This is libc.info, produced by makeinfo version 7.2 from libc.texinfo.

This is ‘The GNU C Library Reference Manual’, for version 2.42.

   Copyright © 1993-2025 Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software Needs Free Documentation" and
"GNU Lesser General Public License", the Front-Cover texts being "A GNU
Manual", and with the Back-Cover Texts as in (a) below.  A copy of the
license is included in the section entitled "GNU Free Documentation
License".

   (a) The FSF's Back-Cover Text is: "You have the freedom to copy and
modify this GNU manual.  Buying copies from the FSF supports it in
developing GNU and promoting software freedom."
INFO-DIR-SECTION Software libraries
START-INFO-DIR-ENTRY
* Libc: (libc).                 C library.
END-INFO-DIR-ENTRY

INFO-DIR-SECTION GNU C library functions and macros
START-INFO-DIR-ENTRY
* ALTWERASE: (libc)Local Modes.
* ARGP_ERR_UNKNOWN: (libc)Argp Parser Functions.
* ARG_MAX: (libc)General Limits.
* BAUD_MAX: (libc)Line Speed.
* BC_BASE_MAX: (libc)Utility Limits.
* BC_DIM_MAX: (libc)Utility Limits.
* BC_SCALE_MAX: (libc)Utility Limits.
* BC_STRING_MAX: (libc)Utility Limits.
* BRKINT: (libc)Input Modes.
* BUFSIZ: (libc)Controlling Buffering.
* CCTS_OFLOW: (libc)Control Modes.
* CHAR_BIT: (libc)Width of Type.
* CHILD_MAX: (libc)General Limits.
* CIGNORE: (libc)Control Modes.
* CLK_TCK: (libc)Processor Time.
* CLOCAL: (libc)Control Modes.
* CLOCKS_PER_SEC: (libc)CPU Time.
* CLOCK_BOOTTIME: (libc)Getting the Time.
* CLOCK_BOOTTIME_ALARM: (libc)Getting the Time.
* CLOCK_MONOTONIC: (libc)Getting the Time.
* CLOCK_MONOTONIC_COARSE: (libc)Getting the Time.
* CLOCK_MONOTONIC_RAW: (libc)Getting the Time.
* CLOCK_PROCESS_CPUTIME_ID: (libc)Getting the Time.
* CLOCK_REALTIME: (libc)Getting the Time.
* CLOCK_REALTIME_ALARM: (libc)Getting the Time.
* CLOCK_REALTIME_COARSE: (libc)Getting the Time.
* CLOCK_TAI: (libc)Getting the Time.
* CLOCK_THREAD_CPUTIME_ID: (libc)Getting the Time.
* COLL_WEIGHTS_MAX: (libc)Utility Limits.
* CPU_ALLOC: (libc)CPU Affinity.
* CPU_ALLOC_SIZE: (libc)CPU Affinity.
* CPU_AND: (libc)CPU Affinity.
* CPU_AND_S: (libc)CPU Affinity.
* CPU_CLR: (libc)CPU Affinity.
* CPU_CLR_S: (libc)CPU Affinity.
* CPU_COUNT: (libc)CPU Affinity.
* CPU_COUNT_S: (libc)CPU Affinity.
* CPU_EQUAL: (libc)CPU Affinity.
* CPU_EQUAL_S: (libc)CPU Affinity.
* CPU_FEATURE_ACTIVE: (libc)X86.
* CPU_FEATURE_PRESENT: (libc)X86.
* CPU_FREE: (libc)CPU Affinity.
* CPU_ISSET: (libc)CPU Affinity.
* CPU_ISSET_S: (libc)CPU Affinity.
* CPU_OR: (libc)CPU Affinity.
* CPU_OR_S: (libc)CPU Affinity.
* CPU_SET: (libc)CPU Affinity.
* CPU_SETSIZE: (libc)CPU Affinity.
* CPU_SET_S: (libc)CPU Affinity.
* CPU_XOR: (libc)CPU Affinity.
* CPU_XOR_S: (libc)CPU Affinity.
* CPU_ZERO: (libc)CPU Affinity.
* CPU_ZERO_S: (libc)CPU Affinity.
* CREAD: (libc)Control Modes.
* CRTS_IFLOW: (libc)Control Modes.
* CS5: (libc)Control Modes.
* CS6: (libc)Control Modes.
* CS7: (libc)Control Modes.
* CS8: (libc)Control Modes.
* CSIZE: (libc)Control Modes.
* CSTOPB: (libc)Control Modes.
* DLFO_EH_SEGMENT_TYPE: (libc)Dynamic Linker Introspection.
* DLFO_STRUCT_HAS_EH_COUNT: (libc)Dynamic Linker Introspection.
* DLFO_STRUCT_HAS_EH_DBASE: (libc)Dynamic Linker Introspection.
* DTTOIF: (libc)Directory Entries.
* E2BIG: (libc)Error Codes.
* EACCES: (libc)Error Codes.
* EADDRINUSE: (libc)Error Codes.
* EADDRNOTAVAIL: (libc)Error Codes.
* EADV: (libc)Error Codes.
* EAFNOSUPPORT: (libc)Error Codes.
* EAGAIN: (libc)Error Codes.
* EALREADY: (libc)Error Codes.
* EAUTH: (libc)Error Codes.
* EBACKGROUND: (libc)Error Codes.
* EBADE: (libc)Error Codes.
* EBADF: (libc)Error Codes.
* EBADFD: (libc)Error Codes.
* EBADMSG: (libc)Error Codes.
* EBADR: (libc)Error Codes.
* EBADRPC: (libc)Error Codes.
* EBADRQC: (libc)Error Codes.
* EBADSLT: (libc)Error Codes.
* EBFONT: (libc)Error Codes.
* EBUSY: (libc)Error Codes.
* ECANCELED: (libc)Error Codes.
* ECHILD: (libc)Error Codes.
* ECHO: (libc)Local Modes.
* ECHOCTL: (libc)Local Modes.
* ECHOE: (libc)Local Modes.
* ECHOK: (libc)Local Modes.
* ECHOKE: (libc)Local Modes.
* ECHONL: (libc)Local Modes.
* ECHOPRT: (libc)Local Modes.
* ECHRNG: (libc)Error Codes.
* ECOMM: (libc)Error Codes.
* ECONNABORTED: (libc)Error Codes.
* ECONNREFUSED: (libc)Error Codes.
* ECONNRESET: (libc)Error Codes.
* ED: (libc)Error Codes.
* EDEADLK: (libc)Error Codes.
* EDEADLOCK: (libc)Error Codes.
* EDESTADDRREQ: (libc)Error Codes.
* EDIED: (libc)Error Codes.
* EDOM: (libc)Error Codes.
* EDOTDOT: (libc)Error Codes.
* EDQUOT: (libc)Error Codes.
* EEXIST: (libc)Error Codes.
* EFAULT: (libc)Error Codes.
* EFBIG: (libc)Error Codes.
* EFTYPE: (libc)Error Codes.
* EGRATUITOUS: (libc)Error Codes.
* EGREGIOUS: (libc)Error Codes.
* EHOSTDOWN: (libc)Error Codes.
* EHOSTUNREACH: (libc)Error Codes.
* EHWPOISON: (libc)Error Codes.
* EIDRM: (libc)Error Codes.
* EIEIO: (libc)Error Codes.
* EILSEQ: (libc)Error Codes.
* EINPROGRESS: (libc)Error Codes.
* EINTR: (libc)Error Codes.
* EINVAL: (libc)Error Codes.
* EIO: (libc)Error Codes.
* EISCONN: (libc)Error Codes.
* EISDIR: (libc)Error Codes.
* EISNAM: (libc)Error Codes.
* EKEYEXPIRED: (libc)Error Codes.
* EKEYREJECTED: (libc)Error Codes.
* EKEYREVOKED: (libc)Error Codes.
* EL2HLT: (libc)Error Codes.
* EL2NSYNC: (libc)Error Codes.
* EL3HLT: (libc)Error Codes.
* EL3RST: (libc)Error Codes.
* ELIBACC: (libc)Error Codes.
* ELIBBAD: (libc)Error Codes.
* ELIBEXEC: (libc)Error Codes.
* ELIBMAX: (libc)Error Codes.
* ELIBSCN: (libc)Error Codes.
* ELNRNG: (libc)Error Codes.
* ELOOP: (libc)Error Codes.
* EMEDIUMTYPE: (libc)Error Codes.
* EMFILE: (libc)Error Codes.
* EMLINK: (libc)Error Codes.
* EMSGSIZE: (libc)Error Codes.
* EMULTIHOP: (libc)Error Codes.
* ENAMETOOLONG: (libc)Error Codes.
* ENAVAIL: (libc)Error Codes.
* ENEEDAUTH: (libc)Error Codes.
* ENETDOWN: (libc)Error Codes.
* ENETRESET: (libc)Error Codes.
* ENETUNREACH: (libc)Error Codes.
* ENFILE: (libc)Error Codes.
* ENOANO: (libc)Error Codes.
* ENOBUFS: (libc)Error Codes.
* ENOCSI: (libc)Error Codes.
* ENODATA: (libc)Error Codes.
* ENODEV: (libc)Error Codes.
* ENOENT: (libc)Error Codes.
* ENOEXEC: (libc)Error Codes.
* ENOKEY: (libc)Error Codes.
* ENOLCK: (libc)Error Codes.
* ENOLINK: (libc)Error Codes.
* ENOMEDIUM: (libc)Error Codes.
* ENOMEM: (libc)Error Codes.
* ENOMSG: (libc)Error Codes.
* ENONET: (libc)Error Codes.
* ENOPKG: (libc)Error Codes.
* ENOPROTOOPT: (libc)Error Codes.
* ENOSPC: (libc)Error Codes.
* ENOSR: (libc)Error Codes.
* ENOSTR: (libc)Error Codes.
* ENOSYS: (libc)Error Codes.
* ENOTBLK: (libc)Error Codes.
* ENOTCONN: (libc)Error Codes.
* ENOTDIR: (libc)Error Codes.
* ENOTEMPTY: (libc)Error Codes.
* ENOTNAM: (libc)Error Codes.
* ENOTRECOVERABLE: (libc)Error Codes.
* ENOTSOCK: (libc)Error Codes.
* ENOTSUP: (libc)Error Codes.
* ENOTTY: (libc)Error Codes.
* ENOTUNIQ: (libc)Error Codes.
* ENXIO: (libc)Error Codes.
* EOF: (libc)EOF and Errors.
* EOPNOTSUPP: (libc)Error Codes.
* EOVERFLOW: (libc)Error Codes.
* EOWNERDEAD: (libc)Error Codes.
* EPERM: (libc)Error Codes.
* EPFNOSUPPORT: (libc)Error Codes.
* EPIPE: (libc)Error Codes.
* EPROCLIM: (libc)Error Codes.
* EPROCUNAVAIL: (libc)Error Codes.
* EPROGMISMATCH: (libc)Error Codes.
* EPROGUNAVAIL: (libc)Error Codes.
* EPROTO: (libc)Error Codes.
* EPROTONOSUPPORT: (libc)Error Codes.
* EPROTOTYPE: (libc)Error Codes.
* EQUIV_CLASS_MAX: (libc)Utility Limits.
* ERANGE: (libc)Error Codes.
* EREMCHG: (libc)Error Codes.
* EREMOTE: (libc)Error Codes.
* EREMOTEIO: (libc)Error Codes.
* ERESTART: (libc)Error Codes.
* ERFKILL: (libc)Error Codes.
* EROFS: (libc)Error Codes.
* ERPCMISMATCH: (libc)Error Codes.
* ESHUTDOWN: (libc)Error Codes.
* ESOCKTNOSUPPORT: (libc)Error Codes.
* ESPIPE: (libc)Error Codes.
* ESRCH: (libc)Error Codes.
* ESRMNT: (libc)Error Codes.
* ESTALE: (libc)Error Codes.
* ESTRPIPE: (libc)Error Codes.
* ETIME: (libc)Error Codes.
* ETIMEDOUT: (libc)Error Codes.
* ETOOMANYREFS: (libc)Error Codes.
* ETXTBSY: (libc)Error Codes.
* EUCLEAN: (libc)Error Codes.
* EUNATCH: (libc)Error Codes.
* EUSERS: (libc)Error Codes.
* EWOULDBLOCK: (libc)Error Codes.
* EXDEV: (libc)Error Codes.
* EXFULL: (libc)Error Codes.
* EXIT_FAILURE: (libc)Exit Status.
* EXIT_SUCCESS: (libc)Exit Status.
* EXPR_NEST_MAX: (libc)Utility Limits.
* FD_CLOEXEC: (libc)Descriptor Flags.
* FD_CLR: (libc)Waiting for I/O.
* FD_ISSET: (libc)Waiting for I/O.
* FD_SET: (libc)Waiting for I/O.
* FD_SETSIZE: (libc)Waiting for I/O.
* FD_ZERO: (libc)Waiting for I/O.
* FE_SNANS_ALWAYS_SIGNAL: (libc)Infinity and NaN.
* FILENAME_MAX: (libc)Limits for Files.
* FLUSHO: (libc)Local Modes.
* FOPEN_MAX: (libc)Opening Streams.
* FP_ILOGB0: (libc)Exponents and Logarithms.
* FP_ILOGBNAN: (libc)Exponents and Logarithms.
* FP_LLOGB0: (libc)Exponents and Logarithms.
* FP_LLOGBNAN: (libc)Exponents and Logarithms.
* F_DUPFD: (libc)Duplicating Descriptors.
* F_GETFD: (libc)Descriptor Flags.
* F_GETFL: (libc)Getting File Status Flags.
* F_GETLK: (libc)File Locks.
* F_GETOWN: (libc)Interrupt Input.
* F_OFD_GETLK: (libc)Open File Description Locks.
* F_OFD_SETLK: (libc)Open File Description Locks.
* F_OFD_SETLKW: (libc)Open File Description Locks.
* F_OK: (libc)Testing File Access.
* F_SETFD: (libc)Descriptor Flags.
* F_SETFL: (libc)Getting File Status Flags.
* F_SETLK: (libc)File Locks.
* F_SETLKW: (libc)File Locks.
* F_SETOWN: (libc)Interrupt Input.
* HUGE_VAL: (libc)Math Error Reporting.
* HUGE_VALF: (libc)Math Error Reporting.
* HUGE_VALL: (libc)Math Error Reporting.
* HUGE_VAL_FN: (libc)Math Error Reporting.
* HUGE_VAL_FNx: (libc)Math Error Reporting.
* HUPCL: (libc)Control Modes.
* I: (libc)Complex Numbers.
* ICANON: (libc)Local Modes.
* ICRNL: (libc)Input Modes.
* IEXTEN: (libc)Local Modes.
* IFNAMSIZ: (libc)Interface Naming.
* IFTODT: (libc)Directory Entries.
* IGNBRK: (libc)Input Modes.
* IGNCR: (libc)Input Modes.
* IGNPAR: (libc)Input Modes.
* IMAXBEL: (libc)Input Modes.
* INADDR_ANY: (libc)Host Address Data Type.
* INADDR_BROADCAST: (libc)Host Address Data Type.
* INADDR_LOOPBACK: (libc)Host Address Data Type.
* INADDR_NONE: (libc)Host Address Data Type.
* INFINITY: (libc)Infinity and NaN.
* INLCR: (libc)Input Modes.
* INPCK: (libc)Input Modes.
* IPPORT_RESERVED: (libc)Ports.
* IPPORT_USERRESERVED: (libc)Ports.
* ISIG: (libc)Local Modes.
* ISTRIP: (libc)Input Modes.
* IXANY: (libc)Input Modes.
* IXOFF: (libc)Input Modes.
* IXON: (libc)Input Modes.
* LINE_MAX: (libc)Utility Limits.
* LINK_MAX: (libc)Limits for Files.
* L_ctermid: (libc)Identifying the Terminal.
* L_cuserid: (libc)Who Logged In.
* L_tmpnam: (libc)Temporary Files.
* MAXNAMLEN: (libc)Limits for Files.
* MAXSYMLINKS: (libc)Symbolic Links.
* MAX_CANON: (libc)Limits for Files.
* MAX_INPUT: (libc)Limits for Files.
* MB_CUR_MAX: (libc)Selecting the Conversion.
* MB_LEN_MAX: (libc)Selecting the Conversion.
* MDMBUF: (libc)Control Modes.
* MSG_DONTROUTE: (libc)Socket Data Options.
* MSG_OOB: (libc)Socket Data Options.
* MSG_PEEK: (libc)Socket Data Options.
* NAME_MAX: (libc)Limits for Files.
* NAN: (libc)Infinity and NaN.
* NCCS: (libc)Mode Data Types.
* NGROUPS_MAX: (libc)General Limits.
* NOFLSH: (libc)Local Modes.
* NOKERNINFO: (libc)Local Modes.
* NSIG: (libc)Standard Signals.
* NULL: (libc)Null Pointer Constant.
* ONLCR: (libc)Output Modes.
* ONOEOT: (libc)Output Modes.
* OPEN_MAX: (libc)General Limits.
* OPOST: (libc)Output Modes.
* OXTABS: (libc)Output Modes.
* O_ACCMODE: (libc)Access Modes.
* O_APPEND: (libc)Operating Modes.
* O_ASYNC: (libc)Operating Modes.
* O_CREAT: (libc)Open-time Flags.
* O_DIRECTORY: (libc)Open-time Flags.
* O_EXCL: (libc)Open-time Flags.
* O_EXEC: (libc)Access Modes.
* O_EXLOCK: (libc)Open-time Flags.
* O_FSYNC: (libc)Operating Modes.
* O_IGNORE_CTTY: (libc)Open-time Flags.
* O_NDELAY: (libc)Operating Modes.
* O_NOATIME: (libc)Operating Modes.
* O_NOCTTY: (libc)Open-time Flags.
* O_NOFOLLOW: (libc)Open-time Flags.
* O_NOLINK: (libc)Open-time Flags.
* O_NONBLOCK: (libc)Open-time Flags.
* O_NONBLOCK: (libc)Operating Modes.
* O_NOTRANS: (libc)Open-time Flags.
* O_PATH: (libc)Access Modes.
* O_RDONLY: (libc)Access Modes.
* O_RDWR: (libc)Access Modes.
* O_READ: (libc)Access Modes.
* O_SHLOCK: (libc)Open-time Flags.
* O_SYNC: (libc)Operating Modes.
* O_TMPFILE: (libc)Open-time Flags.
* O_TRUNC: (libc)Open-time Flags.
* O_WRITE: (libc)Access Modes.
* O_WRONLY: (libc)Access Modes.
* PARENB: (libc)Control Modes.
* PARMRK: (libc)Input Modes.
* PARODD: (libc)Control Modes.
* PATH_MAX: (libc)Limits for Files.
* PA_FLAG_MASK: (libc)Parsing a Template String.
* PENDIN: (libc)Local Modes.
* PF_FILE: (libc)Local Namespace Details.
* PF_INET6: (libc)Internet Namespace.
* PF_INET: (libc)Internet Namespace.
* PF_LOCAL: (libc)Local Namespace Details.
* PF_UNIX: (libc)Local Namespace Details.
* PIPE_BUF: (libc)Limits for Files.
* PTHREAD_ATTR_NO_SIGMASK_NP: (libc)Initial Thread Signal Mask.
* P_tmpdir: (libc)Temporary Files.
* RAND_MAX: (libc)ISO Random.
* RE_DUP_MAX: (libc)General Limits.
* RLIM_INFINITY: (libc)Limits on Resources.
* RSEQ_SIG: (libc)Restartable Sequences.
* R_OK: (libc)Testing File Access.
* SA_NOCLDSTOP: (libc)Flags for Sigaction.
* SA_NOCLDWAIT: (libc)Flags for Sigaction.
* SA_NODEFER: (libc)Flags for Sigaction.
* SA_ONSTACK: (libc)Flags for Sigaction.
* SA_RESETHAND: (libc)Flags for Sigaction.
* SA_RESTART: (libc)Flags for Sigaction.
* SA_SIGINFO: (libc)Flags for Sigaction.
* SEEK_CUR: (libc)File Positioning.
* SEEK_END: (libc)File Positioning.
* SEEK_SET: (libc)File Positioning.
* SIGABRT: (libc)Program Error Signals.
* SIGALRM: (libc)Alarm Signals.
* SIGBUS: (libc)Program Error Signals.
* SIGCHLD: (libc)Job Control Signals.
* SIGCLD: (libc)Job Control Signals.
* SIGCONT: (libc)Job Control Signals.
* SIGEMT: (libc)Program Error Signals.
* SIGFPE: (libc)Program Error Signals.
* SIGHUP: (libc)Termination Signals.
* SIGILL: (libc)Program Error Signals.
* SIGINFO: (libc)Miscellaneous Signals.
* SIGINT: (libc)Termination Signals.
* SIGIO: (libc)Asynchronous I/O Signals.
* SIGIOT: (libc)Program Error Signals.
* SIGKILL: (libc)Termination Signals.
* SIGLOST: (libc)Operation Error Signals.
* SIGPIPE: (libc)Operation Error Signals.
* SIGPOLL: (libc)Asynchronous I/O Signals.
* SIGPROF: (libc)Alarm Signals.
* SIGPWR: (libc)Miscellaneous Signals.
* SIGQUIT: (libc)Termination Signals.
* SIGSEGV: (libc)Program Error Signals.
* SIGSTKFLT: (libc)Program Error Signals.
* SIGSTOP: (libc)Job Control Signals.
* SIGSYS: (libc)Program Error Signals.
* SIGTERM: (libc)Termination Signals.
* SIGTRAP: (libc)Program Error Signals.
* SIGTSTP: (libc)Job Control Signals.
* SIGTTIN: (libc)Job Control Signals.
* SIGTTOU: (libc)Job Control Signals.
* SIGURG: (libc)Asynchronous I/O Signals.
* SIGUSR1: (libc)Miscellaneous Signals.
* SIGUSR2: (libc)Miscellaneous Signals.
* SIGVTALRM: (libc)Alarm Signals.
* SIGWINCH: (libc)Miscellaneous Signals.
* SIGXCPU: (libc)Operation Error Signals.
* SIGXFSZ: (libc)Operation Error Signals.
* SIG_ERR: (libc)Basic Signal Handling.
* SNAN: (libc)Infinity and NaN.
* SNANF: (libc)Infinity and NaN.
* SNANFN: (libc)Infinity and NaN.
* SNANFNx: (libc)Infinity and NaN.
* SNANL: (libc)Infinity and NaN.
* SOCK_DGRAM: (libc)Communication Styles.
* SOCK_RAW: (libc)Communication Styles.
* SOCK_RDM: (libc)Communication Styles.
* SOCK_SEQPACKET: (libc)Communication Styles.
* SOCK_STREAM: (libc)Communication Styles.
* SOL_SOCKET: (libc)Socket-Level Options.
* SPEED_MAX: (libc)Line Speed.
* SSIZE_MAX: (libc)General Limits.
* STREAM_MAX: (libc)General Limits.
* SUN_LEN: (libc)Local Namespace Details.
* S_IFMT: (libc)Testing File Type.
* S_ISBLK: (libc)Testing File Type.
* S_ISCHR: (libc)Testing File Type.
* S_ISDIR: (libc)Testing File Type.
* S_ISFIFO: (libc)Testing File Type.
* S_ISLNK: (libc)Testing File Type.
* S_ISREG: (libc)Testing File Type.
* S_ISSOCK: (libc)Testing File Type.
* S_TYPEISMQ: (libc)Testing File Type.
* S_TYPEISSEM: (libc)Testing File Type.
* S_TYPEISSHM: (libc)Testing File Type.
* TIME_UTC: (libc)Getting the Time.
* TMP_MAX: (libc)Temporary Files.
* TOSTOP: (libc)Local Modes.
* TZNAME_MAX: (libc)General Limits.
* VDISCARD: (libc)Other Special.
* VDSUSP: (libc)Signal Characters.
* VEOF: (libc)Editing Characters.
* VEOL2: (libc)Editing Characters.
* VEOL: (libc)Editing Characters.
* VERASE: (libc)Editing Characters.
* VINTR: (libc)Signal Characters.
* VKILL: (libc)Editing Characters.
* VLNEXT: (libc)Other Special.
* VMIN: (libc)Noncanonical Input.
* VQUIT: (libc)Signal Characters.
* VREPRINT: (libc)Editing Characters.
* VSTART: (libc)Start/Stop Characters.
* VSTATUS: (libc)Other Special.
* VSTOP: (libc)Start/Stop Characters.
* VSUSP: (libc)Signal Characters.
* VTIME: (libc)Noncanonical Input.
* VWERASE: (libc)Editing Characters.
* WCHAR_MAX: (libc)Extended Char Intro.
* WCHAR_MIN: (libc)Extended Char Intro.
* WCOREDUMP: (libc)Process Completion Status.
* WEOF: (libc)EOF and Errors.
* WEOF: (libc)Extended Char Intro.
* WEXITSTATUS: (libc)Process Completion Status.
* WIFEXITED: (libc)Process Completion Status.
* WIFSIGNALED: (libc)Process Completion Status.
* WIFSTOPPED: (libc)Process Completion Status.
* WSTOPSIG: (libc)Process Completion Status.
* WTERMSIG: (libc)Process Completion Status.
* W_OK: (libc)Testing File Access.
* X_OK: (libc)Testing File Access.
* _Complex_I: (libc)Complex Numbers.
* _Exit: (libc)Termination Internals.
* _Fork: (libc)Creating a Process.
* _IOFBF: (libc)Controlling Buffering.
* _IOLBF: (libc)Controlling Buffering.
* _IONBF: (libc)Controlling Buffering.
* _Imaginary_I: (libc)Complex Numbers.
* _PATH_UTMP: (libc)Manipulating the Database.
* _PATH_WTMP: (libc)Manipulating the Database.
* _POSIX2_C_DEV: (libc)System Options.
* _POSIX2_C_VERSION: (libc)Version Supported.
* _POSIX2_FORT_DEV: (libc)System Options.
* _POSIX2_FORT_RUN: (libc)System Options.
* _POSIX2_LOCALEDEF: (libc)System Options.
* _POSIX2_SW_DEV: (libc)System Options.
* _POSIX_CHOWN_RESTRICTED: (libc)Options for Files.
* _POSIX_JOB_CONTROL: (libc)System Options.
* _POSIX_NO_TRUNC: (libc)Options for Files.
* _POSIX_SAVED_IDS: (libc)System Options.
* _POSIX_VDISABLE: (libc)Options for Files.
* _POSIX_VERSION: (libc)Version Supported.
* __fbufsize: (libc)Controlling Buffering.
* __flbf: (libc)Controlling Buffering.
* __fpending: (libc)Controlling Buffering.
* __fpurge: (libc)Flushing Buffers.
* __freadable: (libc)Opening Streams.
* __freading: (libc)Opening Streams.
* __fsetlocking: (libc)Streams and Threads.
* __fwritable: (libc)Opening Streams.
* __fwriting: (libc)Opening Streams.
* __gconv_end_fct: (libc)glibc iconv Implementation.
* __gconv_fct: (libc)glibc iconv Implementation.
* __gconv_init_fct: (libc)glibc iconv Implementation.
* __ppc_get_timebase: (libc)PowerPC.
* __ppc_get_timebase_freq: (libc)PowerPC.
* __ppc_mdoio: (libc)PowerPC.
* __ppc_mdoom: (libc)PowerPC.
* __ppc_set_ppr_low: (libc)PowerPC.
* __ppc_set_ppr_med: (libc)PowerPC.
* __ppc_set_ppr_med_high: (libc)PowerPC.
* __ppc_set_ppr_med_low: (libc)PowerPC.
* __ppc_set_ppr_very_low: (libc)PowerPC.
* __ppc_yield: (libc)PowerPC.
* __riscv_flush_icache: (libc)RISC-V.
* __va_copy: (libc)Argument Macros.
* __x86_get_cpuid_feature_leaf: (libc)X86.
* _dl_find_object: (libc)Dynamic Linker Introspection.
* _exit: (libc)Termination Internals.
* _flushlbf: (libc)Flushing Buffers.
* _tolower: (libc)Case Conversion.
* _toupper: (libc)Case Conversion.
* a64l: (libc)Encode Binary Data.
* abort: (libc)Aborting a Program.
* abs: (libc)Absolute Value.
* accept: (libc)Accepting Connections.
* access: (libc)Testing File Access.
* acos: (libc)Inverse Trig Functions.
* acosf: (libc)Inverse Trig Functions.
* acosfN: (libc)Inverse Trig Functions.
* acosfNx: (libc)Inverse Trig Functions.
* acosh: (libc)Hyperbolic Functions.
* acoshf: (libc)Hyperbolic Functions.
* acoshfN: (libc)Hyperbolic Functions.
* acoshfNx: (libc)Hyperbolic Functions.
* acoshl: (libc)Hyperbolic Functions.
* acosl: (libc)Inverse Trig Functions.
* acospi: (libc)Inverse Trig Functions.
* acospif: (libc)Inverse Trig Functions.
* acospifN: (libc)Inverse Trig Functions.
* acospifNx: (libc)Inverse Trig Functions.
* acospil: (libc)Inverse Trig Functions.
* addmntent: (libc)mtab.
* addseverity: (libc)Adding Severity Classes.
* adjtime: (libc)Setting and Adjusting the Time.
* adjtimex: (libc)Setting and Adjusting the Time.
* aio_cancel64: (libc)Cancel AIO Operations.
* aio_cancel: (libc)Cancel AIO Operations.
* aio_error64: (libc)Status of AIO Operations.
* aio_error: (libc)Status of AIO Operations.
* aio_fsync64: (libc)Synchronizing AIO Operations.
* aio_fsync: (libc)Synchronizing AIO Operations.
* aio_init: (libc)Configuration of AIO.
* aio_read64: (libc)Asynchronous Reads/Writes.
* aio_read: (libc)Asynchronous Reads/Writes.
* aio_return64: (libc)Status of AIO Operations.
* aio_return: (libc)Status of AIO Operations.
* aio_suspend64: (libc)Synchronizing AIO Operations.
* aio_suspend: (libc)Synchronizing AIO Operations.
* aio_write64: (libc)Asynchronous Reads/Writes.
* aio_write: (libc)Asynchronous Reads/Writes.
* alarm: (libc)Setting an Alarm.
* aligned_alloc: (libc)Aligned Memory Blocks.
* alloca: (libc)Variable Size Automatic.
* alphasort64: (libc)Scanning Directory Content.
* alphasort: (libc)Scanning Directory Content.
* arc4random: (libc)High Quality Random.
* arc4random_buf: (libc)High Quality Random.
* arc4random_uniform: (libc)High Quality Random.
* argp_error: (libc)Argp Helper Functions.
* argp_failure: (libc)Argp Helper Functions.
* argp_help: (libc)Argp Help.
* argp_parse: (libc)Argp.
* argp_state_help: (libc)Argp Helper Functions.
* argp_usage: (libc)Argp Helper Functions.
* argz_add: (libc)Argz Functions.
* argz_add_sep: (libc)Argz Functions.
* argz_append: (libc)Argz Functions.
* argz_count: (libc)Argz Functions.
* argz_create: (libc)Argz Functions.
* argz_create_sep: (libc)Argz Functions.
* argz_delete: (libc)Argz Functions.
* argz_extract: (libc)Argz Functions.
* argz_insert: (libc)Argz Functions.
* argz_next: (libc)Argz Functions.
* argz_replace: (libc)Argz Functions.
* argz_stringify: (libc)Argz Functions.
* asctime: (libc)Formatting Calendar Time.
* asctime_r: (libc)Formatting Calendar Time.
* asin: (libc)Inverse Trig Functions.
* asinf: (libc)Inverse Trig Functions.
* asinfN: (libc)Inverse Trig Functions.
* asinfNx: (libc)Inverse Trig Functions.
* asinh: (libc)Hyperbolic Functions.
* asinhf: (libc)Hyperbolic Functions.
* asinhfN: (libc)Hyperbolic Functions.
* asinhfNx: (libc)Hyperbolic Functions.
* asinhl: (libc)Hyperbolic Functions.
* asinl: (libc)Inverse Trig Functions.
* asinpi: (libc)Inverse Trig Functions.
* asinpif: (libc)Inverse Trig Functions.
* asinpifN: (libc)Inverse Trig Functions.
* asinpifNx: (libc)Inverse Trig Functions.
* asinpil: (libc)Inverse Trig Functions.
* asprintf: (libc)Dynamic Output.
* assert: (libc)Consistency Checking.
* assert_perror: (libc)Consistency Checking.
* atan2: (libc)Inverse Trig Functions.
* atan2f: (libc)Inverse Trig Functions.
* atan2fN: (libc)Inverse Trig Functions.
* atan2fNx: (libc)Inverse Trig Functions.
* atan2l: (libc)Inverse Trig Functions.
* atan2pi: (libc)Inverse Trig Functions.
* atan2pif: (libc)Inverse Trig Functions.
* atan2pifN: (libc)Inverse Trig Functions.
* atan2pifNx: (libc)Inverse Trig Functions.
* atan2pil: (libc)Inverse Trig Functions.
* atan: (libc)Inverse Trig Functions.
* atanf: (libc)Inverse Trig Functions.
* atanfN: (libc)Inverse Trig Functions.
* atanfNx: (libc)Inverse Trig Functions.
* atanh: (libc)Hyperbolic Functions.
* atanhf: (libc)Hyperbolic Functions.
* atanhfN: (libc)Hyperbolic Functions.
* atanhfNx: (libc)Hyperbolic Functions.
* atanhl: (libc)Hyperbolic Functions.
* atanl: (libc)Inverse Trig Functions.
* atanpi: (libc)Inverse Trig Functions.
* atanpif: (libc)Inverse Trig Functions.
* atanpifN: (libc)Inverse Trig Functions.
* atanpifNx: (libc)Inverse Trig Functions.
* atanpil: (libc)Inverse Trig Functions.
* atexit: (libc)Cleanups on Exit.
* atof: (libc)Parsing of Floats.
* atoi: (libc)Parsing of Integers.
* atol: (libc)Parsing of Integers.
* atoll: (libc)Parsing of Integers.
* backtrace: (libc)Backtraces.
* backtrace_symbols: (libc)Backtraces.
* backtrace_symbols_fd: (libc)Backtraces.
* basename: (libc)Finding Tokens in a String.
* basename: (libc)Finding Tokens in a String.
* bcmp: (libc)String/Array Comparison.
* bcopy: (libc)Copying Strings and Arrays.
* bind: (libc)Setting Address.
* bind_textdomain_codeset: (libc)Charset conversion in gettext.
* bindtextdomain: (libc)Locating gettext catalog.
* brk: (libc)Resizing the Data Segment.
* bsearch: (libc)Array Search Function.
* btowc: (libc)Converting a Character.
* bzero: (libc)Copying Strings and Arrays.
* cabs: (libc)Absolute Value.
* cabsf: (libc)Absolute Value.
* cabsfN: (libc)Absolute Value.
* cabsfNx: (libc)Absolute Value.
* cabsl: (libc)Absolute Value.
* cacos: (libc)Inverse Trig Functions.
* cacosf: (libc)Inverse Trig Functions.
* cacosfN: (libc)Inverse Trig Functions.
* cacosfNx: (libc)Inverse Trig Functions.
* cacosh: (libc)Hyperbolic Functions.
* cacoshf: (libc)Hyperbolic Functions.
* cacoshfN: (libc)Hyperbolic Functions.
* cacoshfNx: (libc)Hyperbolic Functions.
* cacoshl: (libc)Hyperbolic Functions.
* cacosl: (libc)Inverse Trig Functions.
* call_once: (libc)Call Once.
* calloc: (libc)Allocating Cleared Space.
* canonicalize: (libc)FP Bit Twiddling.
* canonicalize_file_name: (libc)Symbolic Links.
* canonicalizef: (libc)FP Bit Twiddling.
* canonicalizefN: (libc)FP Bit Twiddling.
* canonicalizefNx: (libc)FP Bit Twiddling.
* canonicalizel: (libc)FP Bit Twiddling.
* carg: (libc)Operations on Complex.
* cargf: (libc)Operations on Complex.
* cargfN: (libc)Operations on Complex.
* cargfNx: (libc)Operations on Complex.
* cargl: (libc)Operations on Complex.
* casin: (libc)Inverse Trig Functions.
* casinf: (libc)Inverse Trig Functions.
* casinfN: (libc)Inverse Trig Functions.
* casinfNx: (libc)Inverse Trig Functions.
* casinh: (libc)Hyperbolic Functions.
* casinhf: (libc)Hyperbolic Functions.
* casinhfN: (libc)Hyperbolic Functions.
* casinhfNx: (libc)Hyperbolic Functions.
* casinhl: (libc)Hyperbolic Functions.
* casinl: (libc)Inverse Trig Functions.
* catan: (libc)Inverse Trig Functions.
* catanf: (libc)Inverse Trig Functions.
* catanfN: (libc)Inverse Trig Functions.
* catanfNx: (libc)Inverse Trig Functions.
* catanh: (libc)Hyperbolic Functions.
* catanhf: (libc)Hyperbolic Functions.
* catanhfN: (libc)Hyperbolic Functions.
* catanhfNx: (libc)Hyperbolic Functions.
* catanhl: (libc)Hyperbolic Functions.
* catanl: (libc)Inverse Trig Functions.
* catclose: (libc)The catgets Functions.
* catgets: (libc)The catgets Functions.
* catopen: (libc)The catgets Functions.
* cbrt: (libc)Exponents and Logarithms.
* cbrtf: (libc)Exponents and Logarithms.
* cbrtfN: (libc)Exponents and Logarithms.
* cbrtfNx: (libc)Exponents and Logarithms.
* cbrtl: (libc)Exponents and Logarithms.
* ccos: (libc)Trig Functions.
* ccosf: (libc)Trig Functions.
* ccosfN: (libc)Trig Functions.
* ccosfNx: (libc)Trig Functions.
* ccosh: (libc)Hyperbolic Functions.
* ccoshf: (libc)Hyperbolic Functions.
* ccoshfN: (libc)Hyperbolic Functions.
* ccoshfNx: (libc)Hyperbolic Functions.
* ccoshl: (libc)Hyperbolic Functions.
* ccosl: (libc)Trig Functions.
* ceil: (libc)Rounding Functions.
* ceilf: (libc)Rounding Functions.
* ceilfN: (libc)Rounding Functions.
* ceilfNx: (libc)Rounding Functions.
* ceill: (libc)Rounding Functions.
* cexp: (libc)Exponents and Logarithms.
* cexpf: (libc)Exponents and Logarithms.
* cexpfN: (libc)Exponents and Logarithms.
* cexpfNx: (libc)Exponents and Logarithms.
* cexpl: (libc)Exponents and Logarithms.
* cfgetibaud: (libc)Line Speed.
* cfgetispeed: (libc)Line Speed.
* cfgetobaud: (libc)Line Speed.
* cfgetospeed: (libc)Line Speed.
* cfmakeraw: (libc)Noncanonical Input.
* cfsetbaud: (libc)Line Speed.
* cfsetibaud: (libc)Line Speed.
* cfsetispeed: (libc)Line Speed.
* cfsetobaud: (libc)Line Speed.
* cfsetospeed: (libc)Line Speed.
* cfsetspeed: (libc)Line Speed.
* chdir: (libc)Working Directory.
* chmod: (libc)Setting Permissions.
* chown: (libc)File Owner.
* cimag: (libc)Operations on Complex.
* cimagf: (libc)Operations on Complex.
* cimagfN: (libc)Operations on Complex.
* cimagfNx: (libc)Operations on Complex.
* cimagl: (libc)Operations on Complex.
* clearenv: (libc)Environment Access.
* clearerr: (libc)Error Recovery.
* clearerr_unlocked: (libc)Error Recovery.
* clock: (libc)CPU Time.
* clock_getres: (libc)Getting the Time.
* clock_gettime: (libc)Getting the Time.
* clock_nanosleep: (libc)Sleeping.
* clock_settime: (libc)Setting and Adjusting the Time.
* clog10: (libc)Exponents and Logarithms.
* clog10f: (libc)Exponents and Logarithms.
* clog10fN: (libc)Exponents and Logarithms.
* clog10fNx: (libc)Exponents and Logarithms.
* clog10l: (libc)Exponents and Logarithms.
* clog: (libc)Exponents and Logarithms.
* clogf: (libc)Exponents and Logarithms.
* clogfN: (libc)Exponents and Logarithms.
* clogfNx: (libc)Exponents and Logarithms.
* clogl: (libc)Exponents and Logarithms.
* close: (libc)Opening and Closing Files.
* close_range: (libc)Opening and Closing Files.
* closedir: (libc)Reading/Closing Directory.
* closefrom: (libc)Opening and Closing Files.
* closelog: (libc)closelog.
* cnd_broadcast: (libc)ISO C Condition Variables.
* cnd_destroy: (libc)ISO C Condition Variables.
* cnd_init: (libc)ISO C Condition Variables.
* cnd_signal: (libc)ISO C Condition Variables.
* cnd_timedwait: (libc)ISO C Condition Variables.
* cnd_wait: (libc)ISO C Condition Variables.
* compoundn: (libc)Exponents and Logarithms.
* compoundnf: (libc)Exponents and Logarithms.
* compoundnfN: (libc)Exponents and Logarithms.
* compoundnfNx: (libc)Exponents and Logarithms.
* compoundnl: (libc)Exponents and Logarithms.
* confstr: (libc)String Parameters.
* conj: (libc)Operations on Complex.
* conjf: (libc)Operations on Complex.
* conjfN: (libc)Operations on Complex.
* conjfNx: (libc)Operations on Complex.
* conjl: (libc)Operations on Complex.
* connect: (libc)Connecting.
* copy_file_range: (libc)Copying File Data.
* copysign: (libc)FP Bit Twiddling.
* copysignf: (libc)FP Bit Twiddling.
* copysignfN: (libc)FP Bit Twiddling.
* copysignfNx: (libc)FP Bit Twiddling.
* copysignl: (libc)FP Bit Twiddling.
* cos: (libc)Trig Functions.
* cosf: (libc)Trig Functions.
* cosfN: (libc)Trig Functions.
* cosfNx: (libc)Trig Functions.
* cosh: (libc)Hyperbolic Functions.
* coshf: (libc)Hyperbolic Functions.
* coshfN: (libc)Hyperbolic Functions.
* coshfNx: (libc)Hyperbolic Functions.
* coshl: (libc)Hyperbolic Functions.
* cosl: (libc)Trig Functions.
* cospi: (libc)Trig Functions.
* cospif: (libc)Trig Functions.
* cospifN: (libc)Trig Functions.
* cospifNx: (libc)Trig Functions.
* cospil: (libc)Trig Functions.
* cpow: (libc)Exponents and Logarithms.
* cpowf: (libc)Exponents and Logarithms.
* cpowfN: (libc)Exponents and Logarithms.
* cpowfNx: (libc)Exponents and Logarithms.
* cpowl: (libc)Exponents and Logarithms.
* cproj: (libc)Operations on Complex.
* cprojf: (libc)Operations on Complex.
* cprojfN: (libc)Operations on Complex.
* cprojfNx: (libc)Operations on Complex.
* cprojl: (libc)Operations on Complex.
* creal: (libc)Operations on Complex.
* crealf: (libc)Operations on Complex.
* crealfN: (libc)Operations on Complex.
* crealfNx: (libc)Operations on Complex.
* creall: (libc)Operations on Complex.
* creat64: (libc)Opening and Closing Files.
* creat: (libc)Opening and Closing Files.
* csin: (libc)Trig Functions.
* csinf: (libc)Trig Functions.
* csinfN: (libc)Trig Functions.
* csinfNx: (libc)Trig Functions.
* csinh: (libc)Hyperbolic Functions.
* csinhf: (libc)Hyperbolic Functions.
* csinhfN: (libc)Hyperbolic Functions.
* csinhfNx: (libc)Hyperbolic Functions.
* csinhl: (libc)Hyperbolic Functions.
* csinl: (libc)Trig Functions.
* csqrt: (libc)Exponents and Logarithms.
* csqrtf: (libc)Exponents and Logarithms.
* csqrtfN: (libc)Exponents and Logarithms.
* csqrtfNx: (libc)Exponents and Logarithms.
* csqrtl: (libc)Exponents and Logarithms.
* ctan: (libc)Trig Functions.
* ctanf: (libc)Trig Functions.
* ctanfN: (libc)Trig Functions.
* ctanfNx: (libc)Trig Functions.
* ctanh: (libc)Hyperbolic Functions.
* ctanhf: (libc)Hyperbolic Functions.
* ctanhfN: (libc)Hyperbolic Functions.
* ctanhfNx: (libc)Hyperbolic Functions.
* ctanhl: (libc)Hyperbolic Functions.
* ctanl: (libc)Trig Functions.
* ctermid: (libc)Identifying the Terminal.
* ctime: (libc)Formatting Calendar Time.
* ctime_r: (libc)Formatting Calendar Time.
* cuserid: (libc)Who Logged In.
* daddl: (libc)Misc FP Arithmetic.
* dcgettext: (libc)Translation with gettext.
* dcngettext: (libc)Advanced gettext functions.
* ddivl: (libc)Misc FP Arithmetic.
* dfmal: (libc)Misc FP Arithmetic.
* dgettext: (libc)Translation with gettext.
* difftime: (libc)Calculating Elapsed Time.
* dirfd: (libc)Opening a Directory.
* dirname: (libc)Finding Tokens in a String.
* div: (libc)Integer Division.
* dlinfo: (libc)Dynamic Linker Introspection.
* dmull: (libc)Misc FP Arithmetic.
* dngettext: (libc)Advanced gettext functions.
* dprintf: (libc)Formatted Output Functions.
* drand48: (libc)SVID Random.
* drand48_r: (libc)SVID Random.
* drem: (libc)Remainder Functions.
* dremf: (libc)Remainder Functions.
* dreml: (libc)Remainder Functions.
* dsqrtl: (libc)Misc FP Arithmetic.
* dsubl: (libc)Misc FP Arithmetic.
* dup2: (libc)Duplicating Descriptors.
* dup3: (libc)Duplicating Descriptors.
* dup: (libc)Duplicating Descriptors.
* ecvt: (libc)System V Number Conversion.
* ecvt_r: (libc)System V Number Conversion.
* endfsent: (libc)fstab.
* endgrent: (libc)Scanning All Groups.
* endhostent: (libc)Host Names.
* endmntent: (libc)mtab.
* endnetent: (libc)Networks Database.
* endnetgrent: (libc)Lookup Netgroup.
* endprotoent: (libc)Protocols Database.
* endpwent: (libc)Scanning All Users.
* endservent: (libc)Services Database.
* endutent: (libc)Manipulating the Database.
* endutxent: (libc)XPG Functions.
* envz_add: (libc)Envz Functions.
* envz_entry: (libc)Envz Functions.
* envz_get: (libc)Envz Functions.
* envz_merge: (libc)Envz Functions.
* envz_remove: (libc)Envz Functions.
* envz_strip: (libc)Envz Functions.
* epoll_create: (libc)Other Low-Level I/O APIs.
* epoll_wait: (libc)Other Low-Level I/O APIs.
* erand48: (libc)SVID Random.
* erand48_r: (libc)SVID Random.
* erf: (libc)Special Functions.
* erfc: (libc)Special Functions.
* erfcf: (libc)Special Functions.
* erfcfN: (libc)Special Functions.
* erfcfNx: (libc)Special Functions.
* erfcl: (libc)Special Functions.
* erff: (libc)Special Functions.
* erffN: (libc)Special Functions.
* erffNx: (libc)Special Functions.
* erfl: (libc)Special Functions.
* err: (libc)Error Messages.
* errno: (libc)Checking for Errors.
* error: (libc)Error Messages.
* error_at_line: (libc)Error Messages.
* errx: (libc)Error Messages.
* execl: (libc)Executing a File.
* execle: (libc)Executing a File.
* execlp: (libc)Executing a File.
* execv: (libc)Executing a File.
* execve: (libc)Executing a File.
* execvp: (libc)Executing a File.
* exit: (libc)Normal Termination.
* exp10: (libc)Exponents and Logarithms.
* exp10f: (libc)Exponents and Logarithms.
* exp10fN: (libc)Exponents and Logarithms.
* exp10fNx: (libc)Exponents and Logarithms.
* exp10l: (libc)Exponents and Logarithms.
* exp10m1: (libc)Exponents and Logarithms.
* exp10m1f: (libc)Exponents and Logarithms.
* exp10m1fN: (libc)Exponents and Logarithms.
* exp10m1fNx: (libc)Exponents and Logarithms.
* exp10m1l: (libc)Exponents and Logarithms.
* exp2: (libc)Exponents and Logarithms.
* exp2f: (libc)Exponents and Logarithms.
* exp2fN: (libc)Exponents and Logarithms.
* exp2fNx: (libc)Exponents and Logarithms.
* exp2l: (libc)Exponents and Logarithms.
* exp2m1: (libc)Exponents and Logarithms.
* exp2m1f: (libc)Exponents and Logarithms.
* exp2m1fN: (libc)Exponents and Logarithms.
* exp2m1fNx: (libc)Exponents and Logarithms.
* exp2m1l: (libc)Exponents and Logarithms.
* exp: (libc)Exponents and Logarithms.
* expf: (libc)Exponents and Logarithms.
* expfN: (libc)Exponents and Logarithms.
* expfNx: (libc)Exponents and Logarithms.
* expl: (libc)Exponents and Logarithms.
* explicit_bzero: (libc)Erasing Sensitive Data.
* expm1: (libc)Exponents and Logarithms.
* expm1f: (libc)Exponents and Logarithms.
* expm1fN: (libc)Exponents and Logarithms.
* expm1fNx: (libc)Exponents and Logarithms.
* expm1l: (libc)Exponents and Logarithms.
* fMaddfN: (libc)Misc FP Arithmetic.
* fMaddfNx: (libc)Misc FP Arithmetic.
* fMdivfN: (libc)Misc FP Arithmetic.
* fMdivfNx: (libc)Misc FP Arithmetic.
* fMfmafN: (libc)Misc FP Arithmetic.
* fMfmafNx: (libc)Misc FP Arithmetic.
* fMmulfN: (libc)Misc FP Arithmetic.
* fMmulfNx: (libc)Misc FP Arithmetic.
* fMsqrtfN: (libc)Misc FP Arithmetic.
* fMsqrtfNx: (libc)Misc FP Arithmetic.
* fMsubfN: (libc)Misc FP Arithmetic.
* fMsubfNx: (libc)Misc FP Arithmetic.
* fMxaddfN: (libc)Misc FP Arithmetic.
* fMxaddfNx: (libc)Misc FP Arithmetic.
* fMxdivfN: (libc)Misc FP Arithmetic.
* fMxdivfNx: (libc)Misc FP Arithmetic.
* fMxfmafN: (libc)Misc FP Arithmetic.
* fMxfmafNx: (libc)Misc FP Arithmetic.
* fMxmulfN: (libc)Misc FP Arithmetic.
* fMxmulfNx: (libc)Misc FP Arithmetic.
* fMxsqrtfN: (libc)Misc FP Arithmetic.
* fMxsqrtfNx: (libc)Misc FP Arithmetic.
* fMxsubfN: (libc)Misc FP Arithmetic.
* fMxsubfNx: (libc)Misc FP Arithmetic.
* fabs: (libc)Absolute Value.
* fabsf: (libc)Absolute Value.
* fabsfN: (libc)Absolute Value.
* fabsfNx: (libc)Absolute Value.
* fabsl: (libc)Absolute Value.
* faccessat: (libc)Testing File Access.
* fadd: (libc)Misc FP Arithmetic.
* faddl: (libc)Misc FP Arithmetic.
* fchdir: (libc)Working Directory.
* fchmod: (libc)Setting Permissions.
* fchown: (libc)File Owner.
* fclose: (libc)Closing Streams.
* fcloseall: (libc)Closing Streams.
* fcntl: (libc)Control Operations.
* fcvt: (libc)System V Number Conversion.
* fcvt_r: (libc)System V Number Conversion.
* fdatasync: (libc)Synchronizing I/O.
* fdim: (libc)Misc FP Arithmetic.
* fdimf: (libc)Misc FP Arithmetic.
* fdimfN: (libc)Misc FP Arithmetic.
* fdimfNx: (libc)Misc FP Arithmetic.
* fdiml: (libc)Misc FP Arithmetic.
* fdiv: (libc)Misc FP Arithmetic.
* fdivl: (libc)Misc FP Arithmetic.
* fdopen: (libc)Descriptors and Streams.
* fdopendir: (libc)Opening a Directory.
* feclearexcept: (libc)Status bit operations.
* fedisableexcept: (libc)Control Functions.
* feenableexcept: (libc)Control Functions.
* fegetenv: (libc)Control Functions.
* fegetexcept: (libc)Control Functions.
* fegetexceptflag: (libc)Status bit operations.
* fegetmode: (libc)Control Functions.
* fegetround: (libc)Rounding.
* feholdexcept: (libc)Control Functions.
* feof: (libc)EOF and Errors.
* feof_unlocked: (libc)EOF and Errors.
* feraiseexcept: (libc)Status bit operations.
* ferror: (libc)EOF and Errors.
* ferror_unlocked: (libc)EOF and Errors.
* fesetenv: (libc)Control Functions.
* fesetexcept: (libc)Status bit operations.
* fesetexceptflag: (libc)Status bit operations.
* fesetmode: (libc)Control Functions.
* fesetround: (libc)Rounding.
* fetestexcept: (libc)Status bit operations.
* fetestexceptflag: (libc)Status bit operations.
* feupdateenv: (libc)Control Functions.
* fexecve: (libc)Executing a File.
* fflush: (libc)Flushing Buffers.
* fflush_unlocked: (libc)Flushing Buffers.
* ffma: (libc)Misc FP Arithmetic.
* ffmal: (libc)Misc FP Arithmetic.
* fgetc: (libc)Character Input.
* fgetc_unlocked: (libc)Character Input.
* fgetgrent: (libc)Scanning All Groups.
* fgetgrent_r: (libc)Scanning All Groups.
* fgetpos64: (libc)Portable Positioning.
* fgetpos: (libc)Portable Positioning.
* fgetpwent: (libc)Scanning All Users.
* fgetpwent_r: (libc)Scanning All Users.
* fgets: (libc)Line Input.
* fgets_unlocked: (libc)Line Input.
* fgetwc: (libc)Character Input.
* fgetwc_unlocked: (libc)Character Input.
* fgetws: (libc)Line Input.
* fgetws_unlocked: (libc)Line Input.
* fileno: (libc)Descriptors and Streams.
* fileno_unlocked: (libc)Descriptors and Streams.
* finite: (libc)Floating Point Classes.
* finitef: (libc)Floating Point Classes.
* finitel: (libc)Floating Point Classes.
* flockfile: (libc)Streams and Threads.
* floor: (libc)Rounding Functions.
* floorf: (libc)Rounding Functions.
* floorfN: (libc)Rounding Functions.
* floorfNx: (libc)Rounding Functions.
* floorl: (libc)Rounding Functions.
* fma: (libc)Misc FP Arithmetic.
* fmaf: (libc)Misc FP Arithmetic.
* fmafN: (libc)Misc FP Arithmetic.
* fmafNx: (libc)Misc FP Arithmetic.
* fmal: (libc)Misc FP Arithmetic.
* fmax: (libc)Misc FP Arithmetic.
* fmaxf: (libc)Misc FP Arithmetic.
* fmaxfN: (libc)Misc FP Arithmetic.
* fmaxfNx: (libc)Misc FP Arithmetic.
* fmaximum: (libc)Misc FP Arithmetic.
* fmaximum_mag: (libc)Misc FP Arithmetic.
* fmaximum_mag_num: (libc)Misc FP Arithmetic.
* fmaximum_mag_numf: (libc)Misc FP Arithmetic.
* fmaximum_mag_numfN: (libc)Misc FP Arithmetic.
* fmaximum_mag_numfNx: (libc)Misc FP Arithmetic.
* fmaximum_mag_numl: (libc)Misc FP Arithmetic.
* fmaximum_magf: (libc)Misc FP Arithmetic.
* fmaximum_magfN: (libc)Misc FP Arithmetic.
* fmaximum_magfNx: (libc)Misc FP Arithmetic.
* fmaximum_magl: (libc)Misc FP Arithmetic.
* fmaximum_num: (libc)Misc FP Arithmetic.
* fmaximum_numf: (libc)Misc FP Arithmetic.
* fmaximum_numfN: (libc)Misc FP Arithmetic.
* fmaximum_numfNx: (libc)Misc FP Arithmetic.
* fmaximum_numl: (libc)Misc FP Arithmetic.
* fmaximumf: (libc)Misc FP Arithmetic.
* fmaximumfN: (libc)Misc FP Arithmetic.
* fmaximumfNx: (libc)Misc FP Arithmetic.
* fmaximuml: (libc)Misc FP Arithmetic.
* fmaxl: (libc)Misc FP Arithmetic.
* fmaxmag: (libc)Misc FP Arithmetic.
* fmaxmagf: (libc)Misc FP Arithmetic.
* fmaxmagfN: (libc)Misc FP Arithmetic.
* fmaxmagfNx: (libc)Misc FP Arithmetic.
* fmaxmagl: (libc)Misc FP Arithmetic.
* fmemopen: (libc)String Streams.
* fmin: (libc)Misc FP Arithmetic.
* fminf: (libc)Misc FP Arithmetic.
* fminfN: (libc)Misc FP Arithmetic.
* fminfNx: (libc)Misc FP Arithmetic.
* fminimum: (libc)Misc FP Arithmetic.
* fminimum_mag: (libc)Misc FP Arithmetic.
* fminimum_mag_num: (libc)Misc FP Arithmetic.
* fminimum_mag_numf: (libc)Misc FP Arithmetic.
* fminimum_mag_numfN: (libc)Misc FP Arithmetic.
* fminimum_mag_numfNx: (libc)Misc FP Arithmetic.
* fminimum_mag_numl: (libc)Misc FP Arithmetic.
* fminimum_magf: (libc)Misc FP Arithmetic.
* fminimum_magfN: (libc)Misc FP Arithmetic.
* fminimum_magfNx: (libc)Misc FP Arithmetic.
* fminimum_magl: (libc)Misc FP Arithmetic.
* fminimum_num: (libc)Misc FP Arithmetic.
* fminimum_numf: (libc)Misc FP Arithmetic.
* fminimum_numfN: (libc)Misc FP Arithmetic.
* fminimum_numfNx: (libc)Misc FP Arithmetic.
* fminimum_numl: (libc)Misc FP Arithmetic.
* fminimumf: (libc)Misc FP Arithmetic.
* fminimumfN: (libc)Misc FP Arithmetic.
* fminimumfNx: (libc)Misc FP Arithmetic.
* fminimuml: (libc)Misc FP Arithmetic.
* fminl: (libc)Misc FP Arithmetic.
* fminmag: (libc)Misc FP Arithmetic.
* fminmagf: (libc)Misc FP Arithmetic.
* fminmagfN: (libc)Misc FP Arithmetic.
* fminmagfNx: (libc)Misc FP Arithmetic.
* fminmagl: (libc)Misc FP Arithmetic.
* fmod: (libc)Remainder Functions.
* fmodf: (libc)Remainder Functions.
* fmodfN: (libc)Remainder Functions.
* fmodfNx: (libc)Remainder Functions.
* fmodl: (libc)Remainder Functions.
* fmtmsg: (libc)Printing Formatted Messages.
* fmul: (libc)Misc FP Arithmetic.
* fmull: (libc)Misc FP Arithmetic.
* fnmatch: (libc)Wildcard Matching.
* fopen64: (libc)Opening Streams.
* fopen: (libc)Opening Streams.
* fopencookie: (libc)Streams and Cookies.
* fork: (libc)Creating a Process.
* forkpty: (libc)Pseudo-Terminal Pairs.
* fpathconf: (libc)Pathconf.
* fpclassify: (libc)Floating Point Classes.
* fprintf: (libc)Formatted Output Functions.
* fputc: (libc)Simple Output.
* fputc_unlocked: (libc)Simple Output.
* fputs: (libc)Simple Output.
* fputs_unlocked: (libc)Simple Output.
* fputwc: (libc)Simple Output.
* fputwc_unlocked: (libc)Simple Output.
* fputws: (libc)Simple Output.
* fputws_unlocked: (libc)Simple Output.
* fread: (libc)Block Input/Output.
* fread_unlocked: (libc)Block Input/Output.
* free: (libc)Freeing after Malloc.
* freopen64: (libc)Opening Streams.
* freopen: (libc)Opening Streams.
* frexp: (libc)Normalization Functions.
* frexpf: (libc)Normalization Functions.
* frexpfN: (libc)Normalization Functions.
* frexpfNx: (libc)Normalization Functions.
* frexpl: (libc)Normalization Functions.
* fromfp: (libc)Rounding Functions.
* fromfpf: (libc)Rounding Functions.
* fromfpfN: (libc)Rounding Functions.
* fromfpfNx: (libc)Rounding Functions.
* fromfpl: (libc)Rounding Functions.
* fromfpx: (libc)Rounding Functions.
* fromfpxf: (libc)Rounding Functions.
* fromfpxfN: (libc)Rounding Functions.
* fromfpxfNx: (libc)Rounding Functions.
* fromfpxl: (libc)Rounding Functions.
* fscanf: (libc)Formatted Input Functions.
* fseek: (libc)File Positioning.
* fseeko64: (libc)File Positioning.
* fseeko: (libc)File Positioning.
* fsetpos64: (libc)Portable Positioning.
* fsetpos: (libc)Portable Positioning.
* fsqrt: (libc)Misc FP Arithmetic.
* fsqrtl: (libc)Misc FP Arithmetic.
* fstat64: (libc)Reading Attributes.
* fstat: (libc)Reading Attributes.
* fstatat64: (libc)Reading Attributes.
* fstatat: (libc)Reading Attributes.
* fsub: (libc)Misc FP Arithmetic.
* fsubl: (libc)Misc FP Arithmetic.
* fsync: (libc)Synchronizing I/O.
* ftell: (libc)File Positioning.
* ftello64: (libc)File Positioning.
* ftello: (libc)File Positioning.
* ftruncate64: (libc)File Size.
* ftruncate: (libc)File Size.
* ftrylockfile: (libc)Streams and Threads.
* ftw64: (libc)Working with Directory Trees.
* ftw: (libc)Working with Directory Trees.
* funlockfile: (libc)Streams and Threads.
* futimens: (libc)File Times.
* futimes: (libc)File Times.
* fwide: (libc)Streams and I18N.
* fwprintf: (libc)Formatted Output Functions.
* fwrite: (libc)Block Input/Output.
* fwrite_unlocked: (libc)Block Input/Output.
* fwscanf: (libc)Formatted Input Functions.
* gamma: (libc)Special Functions.
* gammaf: (libc)Special Functions.
* gammal: (libc)Special Functions.
* gcvt: (libc)System V Number Conversion.
* get_avphys_pages: (libc)Query Memory Parameters.
* get_current_dir_name: (libc)Working Directory.
* get_nprocs: (libc)Processor Resources.
* get_nprocs_conf: (libc)Processor Resources.
* get_phys_pages: (libc)Query Memory Parameters.
* getauxval: (libc)Auxiliary Vector.
* getc: (libc)Character Input.
* getc_unlocked: (libc)Character Input.
* getchar: (libc)Character Input.
* getchar_unlocked: (libc)Character Input.
* getcontext: (libc)System V contexts.
* getcpu: (libc)CPU Affinity.
* getcwd: (libc)Working Directory.
* getdate: (libc)General Time String Parsing.
* getdate_r: (libc)General Time String Parsing.
* getdelim: (libc)Line Input.
* getdents64: (libc)Low-level Directory Access.
* getdomainnname: (libc)Host Identification.
* getegid: (libc)Reading Persona.
* getentropy: (libc)Unpredictable Bytes.
* getenv: (libc)Environment Access.
* geteuid: (libc)Reading Persona.
* getfsent: (libc)fstab.
* getfsfile: (libc)fstab.
* getfsspec: (libc)fstab.
* getgid: (libc)Reading Persona.
* getgrent: (libc)Scanning All Groups.
* getgrent_r: (libc)Scanning All Groups.
* getgrgid: (libc)Lookup Group.
* getgrgid_r: (libc)Lookup Group.
* getgrnam: (libc)Lookup Group.
* getgrnam_r: (libc)Lookup Group.
* getgrouplist: (libc)Setting Groups.
* getgroups: (libc)Reading Persona.
* gethostbyaddr: (libc)Host Names.
* gethostbyaddr_r: (libc)Host Names.
* gethostbyname2: (libc)Host Names.
* gethostbyname2_r: (libc)Host Names.
* gethostbyname: (libc)Host Names.
* gethostbyname_r: (libc)Host Names.
* gethostent: (libc)Host Names.
* gethostid: (libc)Host Identification.
* gethostname: (libc)Host Identification.
* getitimer: (libc)Setting an Alarm.
* getline: (libc)Line Input.
* getloadavg: (libc)Processor Resources.
* getlogin: (libc)Who Logged In.
* getmntent: (libc)mtab.
* getmntent_r: (libc)mtab.
* getnetbyaddr: (libc)Networks Database.
* getnetbyname: (libc)Networks Database.
* getnetent: (libc)Networks Database.
* getnetgrent: (libc)Lookup Netgroup.
* getnetgrent_r: (libc)Lookup Netgroup.
* getopt: (libc)Using Getopt.
* getopt_long: (libc)Getopt Long Options.
* getopt_long_only: (libc)Getopt Long Options.
* getpagesize: (libc)Query Memory Parameters.
* getpass: (libc)getpass.
* getpayload: (libc)FP Bit Twiddling.
* getpayloadf: (libc)FP Bit Twiddling.
* getpayloadfN: (libc)FP Bit Twiddling.
* getpayloadfNx: (libc)FP Bit Twiddling.
* getpayloadl: (libc)FP Bit Twiddling.
* getpeername: (libc)Who is Connected.
* getpgid: (libc)Process Group Functions.
* getpgrp: (libc)Process Group Functions.
* getpid: (libc)Process Identification.
* getppid: (libc)Process Identification.
* getpriority: (libc)Traditional Scheduling Functions.
* getprotobyname: (libc)Protocols Database.
* getprotobynumber: (libc)Protocols Database.
* getprotoent: (libc)Protocols Database.
* getpt: (libc)Allocation.
* getpwent: (libc)Scanning All Users.
* getpwent_r: (libc)Scanning All Users.
* getpwnam: (libc)Lookup User.
* getpwnam_r: (libc)Lookup User.
* getpwuid: (libc)Lookup User.
* getpwuid_r: (libc)Lookup User.
* getrandom: (libc)Unpredictable Bytes.
* getrlimit64: (libc)Limits on Resources.
* getrlimit: (libc)Limits on Resources.
* getrusage: (libc)Resource Usage.
* gets: (libc)Line Input.
* getservbyname: (libc)Services Database.
* getservbyport: (libc)Services Database.
* getservent: (libc)Services Database.
* getsid: (libc)Process Group Functions.
* getsockname: (libc)Reading Address.
* getsockopt: (libc)Socket Option Functions.
* getsubopt: (libc)Suboptions.
* gettext: (libc)Translation with gettext.
* gettid: (libc)Process Identification.
* gettimeofday: (libc)Getting the Time.
* getuid: (libc)Reading Persona.
* getumask: (libc)Setting Permissions.
* getutent: (libc)Manipulating the Database.
* getutent_r: (libc)Manipulating the Database.
* getutid: (libc)Manipulating the Database.
* getutid_r: (libc)Manipulating the Database.
* getutline: (libc)Manipulating the Database.
* getutline_r: (libc)Manipulating the Database.
* getutmp: (libc)XPG Functions.
* getutmpx: (libc)XPG Functions.
* getutxent: (libc)XPG Functions.
* getutxid: (libc)XPG Functions.
* getutxline: (libc)XPG Functions.
* getw: (libc)Character Input.
* getwc: (libc)Character Input.
* getwc_unlocked: (libc)Character Input.
* getwchar: (libc)Character Input.
* getwchar_unlocked: (libc)Character Input.
* getwd: (libc)Working Directory.
* glob64: (libc)Calling Glob.
* glob: (libc)Calling Glob.
* globfree64: (libc)More Flags for Globbing.
* globfree: (libc)More Flags for Globbing.
* gmtime: (libc)Broken-down Time.
* gmtime_r: (libc)Broken-down Time.
* grantpt: (libc)Allocation.
* gsignal: (libc)Signaling Yourself.
* gtty: (libc)BSD Terminal Modes.
* hasmntopt: (libc)mtab.
* hcreate: (libc)Hash Search Function.
* hcreate_r: (libc)Hash Search Function.
* hdestroy: (libc)Hash Search Function.
* hdestroy_r: (libc)Hash Search Function.
* hsearch: (libc)Hash Search Function.
* hsearch_r: (libc)Hash Search Function.
* htonl: (libc)Byte Order.
* htons: (libc)Byte Order.
* hypot: (libc)Exponents and Logarithms.
* hypotf: (libc)Exponents and Logarithms.
* hypotfN: (libc)Exponents and Logarithms.
* hypotfNx: (libc)Exponents and Logarithms.
* hypotl: (libc)Exponents and Logarithms.
* iconv: (libc)Generic Conversion Interface.
* iconv_close: (libc)Generic Conversion Interface.
* iconv_open: (libc)Generic Conversion Interface.
* if_freenameindex: (libc)Interface Naming.
* if_indextoname: (libc)Interface Naming.
* if_nameindex: (libc)Interface Naming.
* if_nametoindex: (libc)Interface Naming.
* ilogb: (libc)Exponents and Logarithms.
* ilogbf: (libc)Exponents and Logarithms.
* ilogbfN: (libc)Exponents and Logarithms.
* ilogbfNx: (libc)Exponents and Logarithms.
* ilogbl: (libc)Exponents and Logarithms.
* imaxabs: (libc)Absolute Value.
* imaxdiv: (libc)Integer Division.
* in6addr_any: (libc)Host Address Data Type.
* in6addr_loopback: (libc)Host Address Data Type.
* index: (libc)Search Functions.
* inet_addr: (libc)Host Address Functions.
* inet_aton: (libc)Host Address Functions.
* inet_lnaof: (libc)Host Address Functions.
* inet_makeaddr: (libc)Host Address Functions.
* inet_netof: (libc)Host Address Functions.
* inet_network: (libc)Host Address Functions.
* inet_ntoa: (libc)Host Address Functions.
* inet_ntop: (libc)Host Address Functions.
* inet_pton: (libc)Host Address Functions.
* initgroups: (libc)Setting Groups.
* initstate: (libc)BSD Random.
* initstate_r: (libc)BSD Random.
* innetgr: (libc)Netgroup Membership.
* ioctl: (libc)IOCTLs.
* isalnum: (libc)Classification of Characters.
* isalpha: (libc)Classification of Characters.
* isascii: (libc)Classification of Characters.
* isatty: (libc)Is It a Terminal.
* isblank: (libc)Classification of Characters.
* iscanonical: (libc)Floating Point Classes.
* iscntrl: (libc)Classification of Characters.
* isdigit: (libc)Classification of Characters.
* iseqsig: (libc)FP Comparison Functions.
* isfinite: (libc)Floating Point Classes.
* isgraph: (libc)Classification of Characters.
* isgreater: (libc)FP Comparison Functions.
* isgreaterequal: (libc)FP Comparison Functions.
* isinf: (libc)Floating Point Classes.
* isinff: (libc)Floating Point Classes.
* isinfl: (libc)Floating Point Classes.
* isless: (libc)FP Comparison Functions.
* islessequal: (libc)FP Comparison Functions.
* islessgreater: (libc)FP Comparison Functions.
* islower: (libc)Classification of Characters.
* isnan: (libc)Floating Point Classes.
* isnan: (libc)Floating Point Classes.
* isnanf: (libc)Floating Point Classes.
* isnanl: (libc)Floating Point Classes.
* isnormal: (libc)Floating Point Classes.
* isprint: (libc)Classification of Characters.
* ispunct: (libc)Classification of Characters.
* issignaling: (libc)Floating Point Classes.
* isspace: (libc)Classification of Characters.
* issubnormal: (libc)Floating Point Classes.
* isunordered: (libc)FP Comparison Functions.
* isupper: (libc)Classification of Characters.
* iswalnum: (libc)Classification of Wide Characters.
* iswalpha: (libc)Classification of Wide Characters.
* iswblank: (libc)Classification of Wide Characters.
* iswcntrl: (libc)Classification of Wide Characters.
* iswctype: (libc)Classification of Wide Characters.
* iswdigit: (libc)Classification of Wide Characters.
* iswgraph: (libc)Classification of Wide Characters.
* iswlower: (libc)Classification of Wide Characters.
* iswprint: (libc)Classification of Wide Characters.
* iswpunct: (libc)Classification of Wide Characters.
* iswspace: (libc)Classification of Wide Characters.
* iswupper: (libc)Classification of Wide Characters.
* iswxdigit: (libc)Classification of Wide Characters.
* isxdigit: (libc)Classification of Characters.
* iszero: (libc)Floating Point Classes.
* j0: (libc)Special Functions.
* j0f: (libc)Special Functions.
* j0fN: (libc)Special Functions.
* j0fNx: (libc)Special Functions.
* j0l: (libc)Special Functions.
* j1: (libc)Special Functions.
* j1f: (libc)Special Functions.
* j1fN: (libc)Special Functions.
* j1fNx: (libc)Special Functions.
* j1l: (libc)Special Functions.
* jn: (libc)Special Functions.
* jnf: (libc)Special Functions.
* jnfN: (libc)Special Functions.
* jnfNx: (libc)Special Functions.
* jnl: (libc)Special Functions.
* jrand48: (libc)SVID Random.
* jrand48_r: (libc)SVID Random.
* kill: (libc)Signaling Another Process.
* killpg: (libc)Signaling Another Process.
* l64a: (libc)Encode Binary Data.
* labs: (libc)Absolute Value.
* lcong48: (libc)SVID Random.
* lcong48_r: (libc)SVID Random.
* ldexp: (libc)Normalization Functions.
* ldexpf: (libc)Normalization Functions.
* ldexpfN: (libc)Normalization Functions.
* ldexpfNx: (libc)Normalization Functions.
* ldexpl: (libc)Normalization Functions.
* ldiv: (libc)Integer Division.
* lfind: (libc)Array Search Function.
* lgamma: (libc)Special Functions.
* lgamma_r: (libc)Special Functions.
* lgammaf: (libc)Special Functions.
* lgammafN: (libc)Special Functions.
* lgammafN_r: (libc)Special Functions.
* lgammafNx: (libc)Special Functions.
* lgammafNx_r: (libc)Special Functions.
* lgammaf_r: (libc)Special Functions.
* lgammal: (libc)Special Functions.
* lgammal_r: (libc)Special Functions.
* link: (libc)Hard Links.
* linkat: (libc)Hard Links.
* lio_listio64: (libc)Asynchronous Reads/Writes.
* lio_listio: (libc)Asynchronous Reads/Writes.
* listen: (libc)Listening.
* llabs: (libc)Absolute Value.
* lldiv: (libc)Integer Division.
* llogb: (libc)Exponents and Logarithms.
* llogbf: (libc)Exponents and Logarithms.
* llogbfN: (libc)Exponents and Logarithms.
* llogbfNx: (libc)Exponents and Logarithms.
* llogbl: (libc)Exponents and Logarithms.
* llrint: (libc)Rounding Functions.
* llrintf: (libc)Rounding Functions.
* llrintfN: (libc)Rounding Functions.
* llrintfNx: (libc)Rounding Functions.
* llrintl: (libc)Rounding Functions.
* llround: (libc)Rounding Functions.
* llroundf: (libc)Rounding Functions.
* llroundfN: (libc)Rounding Functions.
* llroundfNx: (libc)Rounding Functions.
* llroundl: (libc)Rounding Functions.
* localeconv: (libc)The Lame Way to Locale Data.
* localtime: (libc)Broken-down Time.
* localtime_r: (libc)Broken-down Time.
* log10: (libc)Exponents and Logarithms.
* log10f: (libc)Exponents and Logarithms.
* log10fN: (libc)Exponents and Logarithms.
* log10fNx: (libc)Exponents and Logarithms.
* log10l: (libc)Exponents and Logarithms.
* log10p1: (libc)Exponents and Logarithms.
* log10p1f: (libc)Exponents and Logarithms.
* log10p1fN: (libc)Exponents and Logarithms.
* log10p1fNx: (libc)Exponents and Logarithms.
* log10p1l: (libc)Exponents and Logarithms.
* log1p: (libc)Exponents and Logarithms.
* log1pf: (libc)Exponents and Logarithms.
* log1pfN: (libc)Exponents and Logarithms.
* log1pfNx: (libc)Exponents and Logarithms.
* log1pl: (libc)Exponents and Logarithms.
* log2: (libc)Exponents and Logarithms.
* log2f: (libc)Exponents and Logarithms.
* log2fN: (libc)Exponents and Logarithms.
* log2fNx: (libc)Exponents and Logarithms.
* log2l: (libc)Exponents and Logarithms.
* log2p1: (libc)Exponents and Logarithms.
* log2p1f: (libc)Exponents and Logarithms.
* log2p1fN: (libc)Exponents and Logarithms.
* log2p1fNx: (libc)Exponents and Logarithms.
* log2p1l: (libc)Exponents and Logarithms.
* log: (libc)Exponents and Logarithms.
* logb: (libc)Exponents and Logarithms.
* logbf: (libc)Exponents and Logarithms.
* logbfN: (libc)Exponents and Logarithms.
* logbfNx: (libc)Exponents and Logarithms.
* logbl: (libc)Exponents and Logarithms.
* logf: (libc)Exponents and Logarithms.
* logfN: (libc)Exponents and Logarithms.
* logfNx: (libc)Exponents and Logarithms.
* login: (libc)Logging In and Out.
* login_tty: (libc)Logging In and Out.
* logl: (libc)Exponents and Logarithms.
* logout: (libc)Logging In and Out.
* logp1: (libc)Exponents and Logarithms.
* logp1f: (libc)Exponents and Logarithms.
* logp1fN: (libc)Exponents and Logarithms.
* logp1fNx: (libc)Exponents and Logarithms.
* logp1l: (libc)Exponents and Logarithms.
* logwtmp: (libc)Logging In and Out.
* longjmp: (libc)Non-Local Details.
* lrand48: (libc)SVID Random.
* lrand48_r: (libc)SVID Random.
* lrint: (libc)Rounding Functions.
* lrintf: (libc)Rounding Functions.
* lrintfN: (libc)Rounding Functions.
* lrintfNx: (libc)Rounding Functions.
* lrintl: (libc)Rounding Functions.
* lround: (libc)Rounding Functions.
* lroundf: (libc)Rounding Functions.
* lroundfN: (libc)Rounding Functions.
* lroundfNx: (libc)Rounding Functions.
* lroundl: (libc)Rounding Functions.
* lsearch: (libc)Array Search Function.
* lseek64: (libc)File Position Primitive.
* lseek: (libc)File Position Primitive.
* lstat64: (libc)Reading Attributes.
* lstat: (libc)Reading Attributes.
* lutimes: (libc)File Times.
* madvise: (libc)Memory-mapped I/O.
* makecontext: (libc)System V contexts.
* mallinfo2: (libc)Statistics of Malloc.
* malloc: (libc)Basic Allocation.
* mallopt: (libc)Malloc Tunable Parameters.
* mblen: (libc)Non-reentrant Character Conversion.
* mbrlen: (libc)Converting a Character.
* mbrtowc: (libc)Converting a Character.
* mbsinit: (libc)Keeping the state.
* mbsnrtowcs: (libc)Converting Strings.
* mbsrtowcs: (libc)Converting Strings.
* mbstowcs: (libc)Non-reentrant String Conversion.
* mbtowc: (libc)Non-reentrant Character Conversion.
* mcheck: (libc)Heap Consistency Checking.
* memalign: (libc)Aligned Memory Blocks.
* memccpy: (libc)Copying Strings and Arrays.
* memchr: (libc)Search Functions.
* memcmp: (libc)String/Array Comparison.
* memcpy: (libc)Copying Strings and Arrays.
* memfd_create: (libc)Memory-mapped I/O.
* memfrob: (libc)Obfuscating Data.
* memmem: (libc)Search Functions.
* memmove: (libc)Copying Strings and Arrays.
* mempcpy: (libc)Copying Strings and Arrays.
* memrchr: (libc)Search Functions.
* memset: (libc)Copying Strings and Arrays.
* mkdir: (libc)Creating Directories.
* mkdirat: (libc)Creating Directories.
* mkdtemp: (libc)Temporary Files.
* mkfifo: (libc)FIFO Special Files.
* mknod: (libc)Making Special Files.
* mkstemp: (libc)Temporary Files.
* mktemp: (libc)Temporary Files.
* mktime: (libc)Broken-down Time.
* mlock2: (libc)Page Lock Functions.
* mlock: (libc)Page Lock Functions.
* mlockall: (libc)Page Lock Functions.
* mmap64: (libc)Memory-mapped I/O.
* mmap: (libc)Memory-mapped I/O.
* modf: (libc)Rounding Functions.
* modff: (libc)Rounding Functions.
* modffN: (libc)Rounding Functions.
* modffNx: (libc)Rounding Functions.
* modfl: (libc)Rounding Functions.
* mount: (libc)Mount-Unmount-Remount.
* mprobe: (libc)Heap Consistency Checking.
* mprotect: (libc)Memory Protection.
* mrand48: (libc)SVID Random.
* mrand48_r: (libc)SVID Random.
* mremap: (libc)Memory-mapped I/O.
* msync: (libc)Memory-mapped I/O.
* mtrace: (libc)Tracing malloc.
* mtx_destroy: (libc)ISO C Mutexes.
* mtx_init: (libc)ISO C Mutexes.
* mtx_lock: (libc)ISO C Mutexes.
* mtx_timedlock: (libc)ISO C Mutexes.
* mtx_trylock: (libc)ISO C Mutexes.
* mtx_unlock: (libc)ISO C Mutexes.
* munlock: (libc)Page Lock Functions.
* munlockall: (libc)Page Lock Functions.
* munmap: (libc)Memory-mapped I/O.
* muntrace: (libc)Tracing malloc.
* nan: (libc)FP Bit Twiddling.
* nanf: (libc)FP Bit Twiddling.
* nanfN: (libc)FP Bit Twiddling.
* nanfNx: (libc)FP Bit Twiddling.
* nanl: (libc)FP Bit Twiddling.
* nanosleep: (libc)Sleeping.
* nearbyint: (libc)Rounding Functions.
* nearbyintf: (libc)Rounding Functions.
* nearbyintfN: (libc)Rounding Functions.
* nearbyintfNx: (libc)Rounding Functions.
* nearbyintl: (libc)Rounding Functions.
* nextafter: (libc)FP Bit Twiddling.
* nextafterf: (libc)FP Bit Twiddling.
* nextafterfN: (libc)FP Bit Twiddling.
* nextafterfNx: (libc)FP Bit Twiddling.
* nextafterl: (libc)FP Bit Twiddling.
* nextdown: (libc)FP Bit Twiddling.
* nextdownf: (libc)FP Bit Twiddling.
* nextdownfN: (libc)FP Bit Twiddling.
* nextdownfNx: (libc)FP Bit Twiddling.
* nextdownl: (libc)FP Bit Twiddling.
* nexttoward: (libc)FP Bit Twiddling.
* nexttowardf: (libc)FP Bit Twiddling.
* nexttowardl: (libc)FP Bit Twiddling.
* nextup: (libc)FP Bit Twiddling.
* nextupf: (libc)FP Bit Twiddling.
* nextupfN: (libc)FP Bit Twiddling.
* nextupfNx: (libc)FP Bit Twiddling.
* nextupl: (libc)FP Bit Twiddling.
* nftw64: (libc)Working with Directory Trees.
* nftw: (libc)Working with Directory Trees.
* ngettext: (libc)Advanced gettext functions.
* nice: (libc)Traditional Scheduling Functions.
* nl_langinfo: (libc)The Elegant and Fast Way.
* nrand48: (libc)SVID Random.
* nrand48_r: (libc)SVID Random.
* ntohl: (libc)Byte Order.
* ntohs: (libc)Byte Order.
* ntp_adjtime: (libc)Setting and Adjusting the Time.
* ntp_gettime: (libc)Setting and Adjusting the Time.
* obstack_1grow: (libc)Growing Objects.
* obstack_1grow_fast: (libc)Extra Fast Growing.
* obstack_alignment_mask: (libc)Obstacks Data Alignment.
* obstack_alloc: (libc)Allocation in an Obstack.
* obstack_base: (libc)Status of an Obstack.
* obstack_blank: (libc)Growing Objects.
* obstack_blank_fast: (libc)Extra Fast Growing.
* obstack_chunk_size: (libc)Obstack Chunks.
* obstack_copy0: (libc)Allocation in an Obstack.
* obstack_copy: (libc)Allocation in an Obstack.
* obstack_finish: (libc)Growing Objects.
* obstack_free: (libc)Freeing Obstack Objects.
* obstack_grow0: (libc)Growing Objects.
* obstack_grow: (libc)Growing Objects.
* obstack_init: (libc)Preparing for Obstacks.
* obstack_int_grow: (libc)Growing Objects.
* obstack_int_grow_fast: (libc)Extra Fast Growing.
* obstack_next_free: (libc)Status of an Obstack.
* obstack_object_size: (libc)Growing Objects.
* obstack_object_size: (libc)Status of an Obstack.
* obstack_printf: (libc)Dynamic Output.
* obstack_ptr_grow: (libc)Growing Objects.
* obstack_ptr_grow_fast: (libc)Extra Fast Growing.
* obstack_room: (libc)Extra Fast Growing.
* obstack_vprintf: (libc)Variable Arguments Output.
* offsetof: (libc)Structure Measurement.
* on_exit: (libc)Cleanups on Exit.
* open64: (libc)Opening and Closing Files.
* open: (libc)Opening and Closing Files.
* open_memstream: (libc)String Streams.
* openat64: (libc)Opening and Closing Files.
* openat: (libc)Opening and Closing Files.
* opendir: (libc)Opening a Directory.
* openlog: (libc)openlog.
* openpty: (libc)Pseudo-Terminal Pairs.
* parse_printf_format: (libc)Parsing a Template String.
* pathconf: (libc)Pathconf.
* pause: (libc)Using Pause.
* pclose: (libc)Pipe to a Subprocess.
* perror: (libc)Error Messages.
* pidfd_getpid: (libc)Querying a Process.
* pipe: (libc)Creating a Pipe.
* pkey_alloc: (libc)Memory Protection.
* pkey_free: (libc)Memory Protection.
* pkey_get: (libc)Memory Protection.
* pkey_mprotect: (libc)Memory Protection.
* pkey_set: (libc)Memory Protection.
* poll: (libc)Other Low-Level I/O APIs.
* popen: (libc)Pipe to a Subprocess.
* posix_fallocate64: (libc)Storage Allocation.
* posix_fallocate: (libc)Storage Allocation.
* posix_memalign: (libc)Aligned Memory Blocks.
* posix_openpt: (libc)Allocation.
* pow: (libc)Exponents and Logarithms.
* powf: (libc)Exponents and Logarithms.
* powfN: (libc)Exponents and Logarithms.
* powfNx: (libc)Exponents and Logarithms.
* powl: (libc)Exponents and Logarithms.
* pown: (libc)Exponents and Logarithms.
* pownf: (libc)Exponents and Logarithms.
* pownfN: (libc)Exponents and Logarithms.
* pownfNx: (libc)Exponents and Logarithms.
* pownl: (libc)Exponents and Logarithms.
* powr: (libc)Exponents and Logarithms.
* powrf: (libc)Exponents and Logarithms.
* powrfN: (libc)Exponents and Logarithms.
* powrfNx: (libc)Exponents and Logarithms.
* powrl: (libc)Exponents and Logarithms.
* pread64: (libc)I/O Primitives.
* pread: (libc)I/O Primitives.
* preadv2: (libc)Scatter-Gather.
* preadv64: (libc)Scatter-Gather.
* preadv64v2: (libc)Scatter-Gather.
* preadv: (libc)Scatter-Gather.
* printf: (libc)Formatted Output Functions.
* printf_size: (libc)Predefined Printf Handlers.
* printf_size_info: (libc)Predefined Printf Handlers.
* psignal: (libc)Signal Messages.
* pthread_attr_destroy: (libc)Creating and Destroying Threads.
* pthread_attr_getaffinity_np: (libc)Thread CPU Affinity.
* pthread_attr_getdetachstate: (libc)Creating and Destroying Threads.
* pthread_attr_getsigmask_np: (libc)Initial Thread Signal Mask.
* pthread_attr_init: (libc)Creating and Destroying Threads.
* pthread_attr_setaffinity_np: (libc)Thread CPU Affinity.
* pthread_attr_setdetachstate: (libc)Creating and Destroying Threads.
* pthread_attr_setsigmask_np: (libc)Initial Thread Signal Mask.
* pthread_barrier_destroy: (libc)POSIX Barriers.
* pthread_barrier_init: (libc)POSIX Barriers.
* pthread_barrier_wait: (libc)POSIX Barriers.
* pthread_clockjoin_np: (libc)Joining Threads.
* pthread_cond_clockwait: (libc)Waiting with Explicit Clocks.
* pthread_create: (libc)Creating and Destroying Threads.
* pthread_detach: (libc)Creating and Destroying Threads.
* pthread_equal: (libc)POSIX Threads Other APIs.
* pthread_getaffinity_np: (libc)Thread CPU Affinity.
* pthread_getattr_default_np: (libc)Default Thread Attributes.
* pthread_getcpuclockid: (libc)POSIX Threads Other APIs.
* pthread_getname_np: (libc)Thread Names.
* pthread_getspecific: (libc)Thread-specific Data.
* pthread_gettid_np: (libc)Process Identification.
* pthread_join: (libc)Creating and Destroying Threads.
* pthread_key_create: (libc)Thread-specific Data.
* pthread_key_delete: (libc)Thread-specific Data.
* pthread_kill: (libc)Creating and Destroying Threads.
* pthread_mutex_clocklock: (libc)POSIX Mutexes.
* pthread_mutex_destroy: (libc)POSIX Mutexes.
* pthread_mutex_init: (libc)POSIX Mutexes.
* pthread_mutex_lock: (libc)POSIX Mutexes.
* pthread_mutex_timedlock: (libc)POSIX Mutexes.
* pthread_mutex_trylock: (libc)POSIX Mutexes.
* pthread_mutex_unlock: (libc)POSIX Mutexes.
* pthread_mutexattr_destroy: (libc)POSIX Mutexes.
* pthread_mutexattr_gettype: (libc)POSIX Mutexes.
* pthread_mutexattr_init: (libc)POSIX Mutexes.
* pthread_mutexattr_settype: (libc)POSIX Mutexes.
* pthread_once: (libc)POSIX Threads Other APIs.
* pthread_rwlock_clockrdlock: (libc)Waiting with Explicit Clocks.
* pthread_rwlock_clockwrlock: (libc)Waiting with Explicit Clocks.
* pthread_self: (libc)Creating and Destroying Threads.
* pthread_setaffinity_np: (libc)Thread CPU Affinity.
* pthread_setattr_default_np: (libc)Default Thread Attributes.
* pthread_setname_np: (libc)Thread Names.
* pthread_setspecific: (libc)Thread-specific Data.
* pthread_sigmask: (libc)POSIX Threads Other APIs.
* pthread_spin_destroy: (libc)POSIX Spin Locks.
* pthread_spin_init: (libc)POSIX Spin Locks.
* pthread_spin_lock: (libc)POSIX Spin Locks.
* pthread_spin_trylock: (libc)POSIX Spin Locks.
* pthread_spin_unlock: (libc)POSIX Spin Locks.
* pthread_timedjoin_np: (libc)Joining Threads.
* pthread_tryjoin_np: (libc)Joining Threads.
* ptsname: (libc)Allocation.
* ptsname_r: (libc)Allocation.
* putc: (libc)Simple Output.
* putc_unlocked: (libc)Simple Output.
* putchar: (libc)Simple Output.
* putchar_unlocked: (libc)Simple Output.
* putenv: (libc)Environment Access.
* putpwent: (libc)Writing a User Entry.
* puts: (libc)Simple Output.
* pututline: (libc)Manipulating the Database.
* pututxline: (libc)XPG Functions.
* putw: (libc)Simple Output.
* putwc: (libc)Simple Output.
* putwc_unlocked: (libc)Simple Output.
* putwchar: (libc)Simple Output.
* putwchar_unlocked: (libc)Simple Output.
* pwrite64: (libc)I/O Primitives.
* pwrite: (libc)I/O Primitives.
* pwritev2: (libc)Scatter-Gather.
* pwritev64: (libc)Scatter-Gather.
* pwritev64v2: (libc)Scatter-Gather.
* pwritev: (libc)Scatter-Gather.
* qecvt: (libc)System V Number Conversion.
* qecvt_r: (libc)System V Number Conversion.
* qfcvt: (libc)System V Number Conversion.
* qfcvt_r: (libc)System V Number Conversion.
* qgcvt: (libc)System V Number Conversion.
* qsort: (libc)Array Sort Function.
* raise: (libc)Signaling Yourself.
* rand: (libc)ISO Random.
* rand_r: (libc)ISO Random.
* random: (libc)BSD Random.
* random_r: (libc)BSD Random.
* rawmemchr: (libc)Search Functions.
* read: (libc)I/O Primitives.
* readdir64: (libc)Reading/Closing Directory.
* readdir64_r: (libc)Reading/Closing Directory.
* readdir: (libc)Reading/Closing Directory.
* readdir_r: (libc)Reading/Closing Directory.
* readlink: (libc)Symbolic Links.
* readv: (libc)Scatter-Gather.
* realloc: (libc)Changing Block Size.
* reallocarray: (libc)Changing Block Size.
* realpath: (libc)Symbolic Links.
* recv: (libc)Receiving Data.
* recvfrom: (libc)Receiving Datagrams.
* recvmsg: (libc)Other Socket APIs.
* regcomp: (libc)POSIX Regexp Compilation.
* regerror: (libc)Regexp Cleanup.
* regexec: (libc)Matching POSIX Regexps.
* regfree: (libc)Regexp Cleanup.
* register_printf_function: (libc)Registering New Conversions.
* remainder: (libc)Remainder Functions.
* remainderf: (libc)Remainder Functions.
* remainderfN: (libc)Remainder Functions.
* remainderfNx: (libc)Remainder Functions.
* remainderl: (libc)Remainder Functions.
* remove: (libc)Deleting Files.
* rename: (libc)Renaming Files.
* renameat: (libc)Renaming Files.
* rewind: (libc)File Positioning.
* rewinddir: (libc)Random Access Directory.
* rindex: (libc)Search Functions.
* rint: (libc)Rounding Functions.
* rintf: (libc)Rounding Functions.
* rintfN: (libc)Rounding Functions.
* rintfNx: (libc)Rounding Functions.
* rintl: (libc)Rounding Functions.
* rmdir: (libc)Deleting Files.
* rootn: (libc)Exponents and Logarithms.
* rootnf: (libc)Exponents and Logarithms.
* rootnfN: (libc)Exponents and Logarithms.
* rootnfNx: (libc)Exponents and Logarithms.
* rootnl: (libc)Exponents and Logarithms.
* round: (libc)Rounding Functions.
* roundeven: (libc)Rounding Functions.
* roundevenf: (libc)Rounding Functions.
* roundevenfN: (libc)Rounding Functions.
* roundevenfNx: (libc)Rounding Functions.
* roundevenl: (libc)Rounding Functions.
* roundf: (libc)Rounding Functions.
* roundfN: (libc)Rounding Functions.
* roundfNx: (libc)Rounding Functions.
* roundl: (libc)Rounding Functions.
* rpmatch: (libc)Yes-or-No Questions.
* rsqrt: (libc)Exponents and Logarithms.
* rsqrtf: (libc)Exponents and Logarithms.
* rsqrtfN: (libc)Exponents and Logarithms.
* rsqrtfNx: (libc)Exponents and Logarithms.
* rsqrtl: (libc)Exponents and Logarithms.
* sbrk: (libc)Resizing the Data Segment.
* scalb: (libc)Normalization Functions.
* scalbf: (libc)Normalization Functions.
* scalbl: (libc)Normalization Functions.
* scalbln: (libc)Normalization Functions.
* scalblnf: (libc)Normalization Functions.
* scalblnfN: (libc)Normalization Functions.
* scalblnfNx: (libc)Normalization Functions.
* scalblnl: (libc)Normalization Functions.
* scalbn: (libc)Normalization Functions.
* scalbnf: (libc)Normalization Functions.
* scalbnfN: (libc)Normalization Functions.
* scalbnfNx: (libc)Normalization Functions.
* scalbnl: (libc)Normalization Functions.
* scandir64: (libc)Scanning Directory Content.
* scandir: (libc)Scanning Directory Content.
* scanf: (libc)Formatted Input Functions.
* sched_get_priority_max: (libc)Basic Scheduling Functions.
* sched_get_priority_min: (libc)Basic Scheduling Functions.
* sched_getaffinity: (libc)CPU Affinity.
* sched_getattr: (libc)Extensible Scheduling.
* sched_getcpu: (libc)CPU Affinity.
* sched_getparam: (libc)Basic Scheduling Functions.
* sched_getscheduler: (libc)Basic Scheduling Functions.
* sched_rr_get_interval: (libc)Basic Scheduling Functions.
* sched_setaffinity: (libc)CPU Affinity.
* sched_setattr: (libc)Extensible Scheduling.
* sched_setparam: (libc)Basic Scheduling Functions.
* sched_setscheduler: (libc)Basic Scheduling Functions.
* sched_yield: (libc)Basic Scheduling Functions.
* secure_getenv: (libc)Environment Access.
* seed48: (libc)SVID Random.
* seed48_r: (libc)SVID Random.
* seekdir: (libc)Random Access Directory.
* select: (libc)Waiting for I/O.
* sem_clockwait: (libc)POSIX Semaphores.
* sem_close: (libc)POSIX Semaphores.
* sem_destroy: (libc)POSIX Semaphores.
* sem_getvalue: (libc)POSIX Semaphores.
* sem_init: (libc)POSIX Semaphores.
* sem_open: (libc)POSIX Semaphores.
* sem_post: (libc)POSIX Semaphores.
* sem_timedwait: (libc)POSIX Semaphores.
* sem_trywait: (libc)POSIX Semaphores.
* sem_unlink: (libc)POSIX Semaphores.
* sem_wait: (libc)POSIX Semaphores.
* semctl: (libc)Semaphores.
* semget: (libc)Semaphores.
* semop: (libc)Semaphores.
* semtimedop: (libc)Semaphores.
* send: (libc)Sending Data.
* sendmsg: (libc)Other Socket APIs.
* sendto: (libc)Sending Datagrams.
* setbuf: (libc)Controlling Buffering.
* setbuffer: (libc)Controlling Buffering.
* setcontext: (libc)System V contexts.
* setdomainname: (libc)Host Identification.
* setegid: (libc)Setting Groups.
* setenv: (libc)Environment Access.
* seteuid: (libc)Setting User ID.
* setfsent: (libc)fstab.
* setgid: (libc)Setting Groups.
* setgrent: (libc)Scanning All Groups.
* setgroups: (libc)Setting Groups.
* sethostent: (libc)Host Names.
* sethostid: (libc)Host Identification.
* sethostname: (libc)Host Identification.
* setitimer: (libc)Setting an Alarm.
* setjmp: (libc)Non-Local Details.
* setlinebuf: (libc)Controlling Buffering.
* setlocale: (libc)Setting the Locale.
* setlogmask: (libc)setlogmask.
* setmntent: (libc)mtab.
* setnetent: (libc)Networks Database.
* setnetgrent: (libc)Lookup Netgroup.
* setpayload: (libc)FP Bit Twiddling.
* setpayloadf: (libc)FP Bit Twiddling.
* setpayloadfN: (libc)FP Bit Twiddling.
* setpayloadfNx: (libc)FP Bit Twiddling.
* setpayloadl: (libc)FP Bit Twiddling.
* setpayloadsig: (libc)FP Bit Twiddling.
* setpayloadsigf: (libc)FP Bit Twiddling.
* setpayloadsigfN: (libc)FP Bit Twiddling.
* setpayloadsigfNx: (libc)FP Bit Twiddling.
* setpayloadsigl: (libc)FP Bit Twiddling.
* setpgid: (libc)Process Group Functions.
* setpgrp: (libc)Process Group Functions.
* setpriority: (libc)Traditional Scheduling Functions.
* setprotoent: (libc)Protocols Database.
* setpwent: (libc)Scanning All Users.
* setregid: (libc)Setting Groups.
* setreuid: (libc)Setting User ID.
* setrlimit64: (libc)Limits on Resources.
* setrlimit: (libc)Limits on Resources.
* setservent: (libc)Services Database.
* setsid: (libc)Process Group Functions.
* setsockopt: (libc)Socket Option Functions.
* setstate: (libc)BSD Random.
* setstate_r: (libc)BSD Random.
* settimeofday: (libc)Setting and Adjusting the Time.
* setuid: (libc)Setting User ID.
* setutent: (libc)Manipulating the Database.
* setutxent: (libc)XPG Functions.
* setvbuf: (libc)Controlling Buffering.
* shm_open: (libc)Memory-mapped I/O.
* shm_unlink: (libc)Memory-mapped I/O.
* shutdown: (libc)Closing a Socket.
* sigabbrev_np: (libc)Signal Messages.
* sigaction: (libc)Advanced Signal Handling.
* sigaddset: (libc)Signal Sets.
* sigaltstack: (libc)Signal Stack.
* sigblock: (libc)BSD Signal Handling.
* sigdelset: (libc)Signal Sets.
* sigdescr_np: (libc)Signal Messages.
* sigemptyset: (libc)Signal Sets.
* sigfillset: (libc)Signal Sets.
* siginterrupt: (libc)BSD Signal Handling.
* sigismember: (libc)Signal Sets.
* siglongjmp: (libc)Non-Local Exits and Signals.
* sigmask: (libc)BSD Signal Handling.
* signal: (libc)Basic Signal Handling.
* signbit: (libc)FP Bit Twiddling.
* significand: (libc)Normalization Functions.
* significandf: (libc)Normalization Functions.
* significandl: (libc)Normalization Functions.
* sigpause: (libc)BSD Signal Handling.
* sigpending: (libc)Checking for Pending Signals.
* sigprocmask: (libc)Process Signal Mask.
* sigsetjmp: (libc)Non-Local Exits and Signals.
* sigsetmask: (libc)BSD Signal Handling.
* sigstack: (libc)Signal Stack.
* sigsuspend: (libc)Sigsuspend.
* sin: (libc)Trig Functions.
* sincos: (libc)Trig Functions.
* sincosf: (libc)Trig Functions.
* sincosfN: (libc)Trig Functions.
* sincosfNx: (libc)Trig Functions.
* sincosl: (libc)Trig Functions.
* sinf: (libc)Trig Functions.
* sinfN: (libc)Trig Functions.
* sinfNx: (libc)Trig Functions.
* sinh: (libc)Hyperbolic Functions.
* sinhf: (libc)Hyperbolic Functions.
* sinhfN: (libc)Hyperbolic Functions.
* sinhfNx: (libc)Hyperbolic Functions.
* sinhl: (libc)Hyperbolic Functions.
* sinl: (libc)Trig Functions.
* sinpi: (libc)Trig Functions.
* sinpif: (libc)Trig Functions.
* sinpifN: (libc)Trig Functions.
* sinpifNx: (libc)Trig Functions.
* sinpil: (libc)Trig Functions.
* sleep: (libc)Sleeping.
* snprintf: (libc)Formatted Output Functions.
* socket: (libc)Creating a Socket.
* socketpair: (libc)Socket Pairs.
* sprintf: (libc)Formatted Output Functions.
* sqrt: (libc)Exponents and Logarithms.
* sqrtf: (libc)Exponents and Logarithms.
* sqrtfN: (libc)Exponents and Logarithms.
* sqrtfNx: (libc)Exponents and Logarithms.
* sqrtl: (libc)Exponents and Logarithms.
* srand48: (libc)SVID Random.
* srand48_r: (libc)SVID Random.
* srand: (libc)ISO Random.
* srandom: (libc)BSD Random.
* srandom_r: (libc)BSD Random.
* sscanf: (libc)Formatted Input Functions.
* ssignal: (libc)Basic Signal Handling.
* stat64: (libc)Reading Attributes.
* stat: (libc)Reading Attributes.
* stdc_bit_ceil_uc: (libc)Bit Manipulation.
* stdc_bit_ceil_ui: (libc)Bit Manipulation.
* stdc_bit_ceil_ul: (libc)Bit Manipulation.
* stdc_bit_ceil_ull: (libc)Bit Manipulation.
* stdc_bit_ceil_us: (libc)Bit Manipulation.
* stdc_bit_floor_uc: (libc)Bit Manipulation.
* stdc_bit_floor_ui: (libc)Bit Manipulation.
* stdc_bit_floor_ul: (libc)Bit Manipulation.
* stdc_bit_floor_ull: (libc)Bit Manipulation.
* stdc_bit_floor_us: (libc)Bit Manipulation.
* stdc_bit_width_uc: (libc)Bit Manipulation.
* stdc_bit_width_ui: (libc)Bit Manipulation.
* stdc_bit_width_ul: (libc)Bit Manipulation.
* stdc_bit_width_ull: (libc)Bit Manipulation.
* stdc_bit_width_us: (libc)Bit Manipulation.
* stdc_count_ones_uc: (libc)Bit Manipulation.
* stdc_count_ones_ui: (libc)Bit Manipulation.
* stdc_count_ones_ul: (libc)Bit Manipulation.
* stdc_count_ones_ull: (libc)Bit Manipulation.
* stdc_count_ones_us: (libc)Bit Manipulation.
* stdc_count_zeros_uc: (libc)Bit Manipulation.
* stdc_count_zeros_ui: (libc)Bit Manipulation.
* stdc_count_zeros_ul: (libc)Bit Manipulation.
* stdc_count_zeros_ull: (libc)Bit Manipulation.
* stdc_count_zeros_us: (libc)Bit Manipulation.
* stdc_first_leading_one_uc: (libc)Bit Manipulation.
* stdc_first_leading_one_ui: (libc)Bit Manipulation.
* stdc_first_leading_one_ul: (libc)Bit Manipulation.
* stdc_first_leading_one_ull: (libc)Bit Manipulation.
* stdc_first_leading_one_us: (libc)Bit Manipulation.
* stdc_first_leading_zero_uc: (libc)Bit Manipulation.
* stdc_first_leading_zero_ui: (libc)Bit Manipulation.
* stdc_first_leading_zero_ul: (libc)Bit Manipulation.
* stdc_first_leading_zero_ull: (libc)Bit Manipulation.
* stdc_first_leading_zero_us: (libc)Bit Manipulation.
* stdc_first_trailing_one_uc: (libc)Bit Manipulation.
* stdc_first_trailing_one_ui: (libc)Bit Manipulation.
* stdc_first_trailing_one_ul: (libc)Bit Manipulation.
* stdc_first_trailing_one_ull: (libc)Bit Manipulation.
* stdc_first_trailing_one_us: (libc)Bit Manipulation.
* stdc_first_trailing_zero_uc: (libc)Bit Manipulation.
* stdc_first_trailing_zero_ui: (libc)Bit Manipulation.
* stdc_first_trailing_zero_ul: (libc)Bit Manipulation.
* stdc_first_trailing_zero_ull: (libc)Bit Manipulation.
* stdc_first_trailing_zero_us: (libc)Bit Manipulation.
* stdc_has_single_bit_uc: (libc)Bit Manipulation.
* stdc_has_single_bit_ui: (libc)Bit Manipulation.
* stdc_has_single_bit_ul: (libc)Bit Manipulation.
* stdc_has_single_bit_ull: (libc)Bit Manipulation.
* stdc_has_single_bit_us: (libc)Bit Manipulation.
* stdc_leading_ones_uc: (libc)Bit Manipulation.
* stdc_leading_ones_ui: (libc)Bit Manipulation.
* stdc_leading_ones_ul: (libc)Bit Manipulation.
* stdc_leading_ones_ull: (libc)Bit Manipulation.
* stdc_leading_ones_us: (libc)Bit Manipulation.
* stdc_leading_zeros_uc: (libc)Bit Manipulation.
* stdc_leading_zeros_ui: (libc)Bit Manipulation.
* stdc_leading_zeros_ul: (libc)Bit Manipulation.
* stdc_leading_zeros_ull: (libc)Bit Manipulation.
* stdc_leading_zeros_us: (libc)Bit Manipulation.
* stdc_trailing_ones_uc: (libc)Bit Manipulation.
* stdc_trailing_ones_ui: (libc)Bit Manipulation.
* stdc_trailing_ones_ul: (libc)Bit Manipulation.
* stdc_trailing_ones_ull: (libc)Bit Manipulation.
* stdc_trailing_ones_us: (libc)Bit Manipulation.
* stdc_trailing_zeros_uc: (libc)Bit Manipulation.
* stdc_trailing_zeros_ui: (libc)Bit Manipulation.
* stdc_trailing_zeros_ul: (libc)Bit Manipulation.
* stdc_trailing_zeros_ull: (libc)Bit Manipulation.
* stdc_trailing_zeros_us: (libc)Bit Manipulation.
* stime: (libc)Setting and Adjusting the Time.
* stpcpy: (libc)Copying Strings and Arrays.
* stpncpy: (libc)Truncating Strings.
* strcasecmp: (libc)String/Array Comparison.
* strcasestr: (libc)Search Functions.
* strcat: (libc)Concatenating Strings.
* strchr: (libc)Search Functions.
* strchrnul: (libc)Search Functions.
* strcmp: (libc)String/Array Comparison.
* strcoll: (libc)Collation Functions.
* strcpy: (libc)Copying Strings and Arrays.
* strcspn: (libc)Search Functions.
* strdup: (libc)Copying Strings and Arrays.
* strdupa: (libc)Copying Strings and Arrays.
* strerror: (libc)Error Messages.
* strerror_l: (libc)Error Messages.
* strerror_r: (libc)Error Messages.
* strerror_r: (libc)Error Messages.
* strerrordesc_np: (libc)Error Messages.
* strerrorname_np: (libc)Error Messages.
* strfmon: (libc)Formatting Numbers.
* strfromd: (libc)Printing of Floats.
* strfromf: (libc)Printing of Floats.
* strfromfN: (libc)Printing of Floats.
* strfromfNx: (libc)Printing of Floats.
* strfroml: (libc)Printing of Floats.
* strfry: (libc)Shuffling Bytes.
* strftime: (libc)Formatting Calendar Time.
* strftime_l: (libc)Formatting Calendar Time.
* strlcat: (libc)Truncating Strings.
* strlcpy: (libc)Truncating Strings.
* strlen: (libc)String Length.
* strncasecmp: (libc)String/Array Comparison.
* strncat: (libc)Truncating Strings.
* strncmp: (libc)String/Array Comparison.
* strncpy: (libc)Truncating Strings.
* strndup: (libc)Truncating Strings.
* strndupa: (libc)Truncating Strings.
* strnlen: (libc)String Length.
* strpbrk: (libc)Search Functions.
* strptime: (libc)Low-Level Time String Parsing.
* strrchr: (libc)Search Functions.
* strsep: (libc)Finding Tokens in a String.
* strsignal: (libc)Signal Messages.
* strspn: (libc)Search Functions.
* strstr: (libc)Search Functions.
* strtod: (libc)Parsing of Floats.
* strtof: (libc)Parsing of Floats.
* strtofN: (libc)Parsing of Floats.
* strtofNx: (libc)Parsing of Floats.
* strtoimax: (libc)Parsing of Integers.
* strtok: (libc)Finding Tokens in a String.
* strtok_r: (libc)Finding Tokens in a String.
* strtol: (libc)Parsing of Integers.
* strtold: (libc)Parsing of Floats.
* strtoll: (libc)Parsing of Integers.
* strtoq: (libc)Parsing of Integers.
* strtoul: (libc)Parsing of Integers.
* strtoull: (libc)Parsing of Integers.
* strtoumax: (libc)Parsing of Integers.
* strtouq: (libc)Parsing of Integers.
* strverscmp: (libc)String/Array Comparison.
* strxfrm: (libc)Collation Functions.
* stty: (libc)BSD Terminal Modes.
* swapcontext: (libc)System V contexts.
* swprintf: (libc)Formatted Output Functions.
* swscanf: (libc)Formatted Input Functions.
* symlink: (libc)Symbolic Links.
* sync: (libc)Synchronizing I/O.
* syscall: (libc)System Calls.
* sysconf: (libc)Sysconf Definition.
* syslog: (libc)syslog; vsyslog.
* system: (libc)Running a Command.
* sysv_signal: (libc)Basic Signal Handling.
* tan: (libc)Trig Functions.
* tanf: (libc)Trig Functions.
* tanfN: (libc)Trig Functions.
* tanfNx: (libc)Trig Functions.
* tanh: (libc)Hyperbolic Functions.
* tanhf: (libc)Hyperbolic Functions.
* tanhfN: (libc)Hyperbolic Functions.
* tanhfNx: (libc)Hyperbolic Functions.
* tanhl: (libc)Hyperbolic Functions.
* tanl: (libc)Trig Functions.
* tanpi: (libc)Trig Functions.
* tanpif: (libc)Trig Functions.
* tanpifN: (libc)Trig Functions.
* tanpifNx: (libc)Trig Functions.
* tanpil: (libc)Trig Functions.
* tcdrain: (libc)Line Control.
* tcflow: (libc)Line Control.
* tcflush: (libc)Line Control.
* tcgetattr: (libc)Mode Functions.
* tcgetpgrp: (libc)Terminal Access Functions.
* tcgetsid: (libc)Terminal Access Functions.
* tcsendbreak: (libc)Line Control.
* tcsetattr: (libc)Mode Functions.
* tcsetpgrp: (libc)Terminal Access Functions.
* tdelete: (libc)Tree Search Function.
* tdestroy: (libc)Tree Search Function.
* telldir: (libc)Random Access Directory.
* tempnam: (libc)Temporary Files.
* textdomain: (libc)Locating gettext catalog.
* tfind: (libc)Tree Search Function.
* tgamma: (libc)Special Functions.
* tgammaf: (libc)Special Functions.
* tgammafN: (libc)Special Functions.
* tgammafNx: (libc)Special Functions.
* tgammal: (libc)Special Functions.
* tgkill: (libc)Signaling Another Process.
* thrd_create: (libc)ISO C Thread Management.
* thrd_current: (libc)ISO C Thread Management.
* thrd_detach: (libc)ISO C Thread Management.
* thrd_equal: (libc)ISO C Thread Management.
* thrd_exit: (libc)ISO C Thread Management.
* thrd_join: (libc)ISO C Thread Management.
* thrd_sleep: (libc)ISO C Thread Management.
* thrd_yield: (libc)ISO C Thread Management.
* time: (libc)Getting the Time.
* timegm: (libc)Broken-down Time.
* timelocal: (libc)Broken-down Time.
* times: (libc)Processor Time.
* timespec_get: (libc)Getting the Time.
* timespec_getres: (libc)Getting the Time.
* tmpfile64: (libc)Temporary Files.
* tmpfile: (libc)Temporary Files.
* tmpnam: (libc)Temporary Files.
* tmpnam_r: (libc)Temporary Files.
* toascii: (libc)Case Conversion.
* tolower: (libc)Case Conversion.
* totalorder: (libc)FP Comparison Functions.
* totalorderf: (libc)FP Comparison Functions.
* totalorderfN: (libc)FP Comparison Functions.
* totalorderfNx: (libc)FP Comparison Functions.
* totalorderl: (libc)FP Comparison Functions.
* totalordermag: (libc)FP Comparison Functions.
* totalordermagf: (libc)FP Comparison Functions.
* totalordermagfN: (libc)FP Comparison Functions.
* totalordermagfNx: (libc)FP Comparison Functions.
* totalordermagl: (libc)FP Comparison Functions.
* toupper: (libc)Case Conversion.
* towctrans: (libc)Wide Character Case Conversion.
* towlower: (libc)Wide Character Case Conversion.
* towupper: (libc)Wide Character Case Conversion.
* trunc: (libc)Rounding Functions.
* truncate64: (libc)File Size.
* truncate: (libc)File Size.
* truncf: (libc)Rounding Functions.
* truncfN: (libc)Rounding Functions.
* truncfNx: (libc)Rounding Functions.
* truncl: (libc)Rounding Functions.
* tsearch: (libc)Tree Search Function.
* tss_create: (libc)ISO C Thread-local Storage.
* tss_delete: (libc)ISO C Thread-local Storage.
* tss_get: (libc)ISO C Thread-local Storage.
* tss_set: (libc)ISO C Thread-local Storage.
* ttyname: (libc)Is It a Terminal.
* ttyname_r: (libc)Is It a Terminal.
* twalk: (libc)Tree Search Function.
* twalk_r: (libc)Tree Search Function.
* tzset: (libc)Time Zone State.
* uabs: (libc)Absolute Value.
* ufromfp: (libc)Rounding Functions.
* ufromfpf: (libc)Rounding Functions.
* ufromfpfN: (libc)Rounding Functions.
* ufromfpfNx: (libc)Rounding Functions.
* ufromfpl: (libc)Rounding Functions.
* ufromfpx: (libc)Rounding Functions.
* ufromfpxf: (libc)Rounding Functions.
* ufromfpxfN: (libc)Rounding Functions.
* ufromfpxfNx: (libc)Rounding Functions.
* ufromfpxl: (libc)Rounding Functions.
* uimaxabs: (libc)Absolute Value.
* ulabs: (libc)Absolute Value.
* ulimit: (libc)Limits on Resources.
* ullabs: (libc)Absolute Value.
* umask: (libc)Setting Permissions.
* umount2: (libc)Mount-Unmount-Remount.
* umount: (libc)Mount-Unmount-Remount.
* uname: (libc)Platform Type.
* ungetc: (libc)How Unread.
* ungetwc: (libc)How Unread.
* unlink: (libc)Deleting Files.
* unlinkat: (libc)Deleting Files.
* unlockpt: (libc)Allocation.
* unsetenv: (libc)Environment Access.
* updwtmp: (libc)Manipulating the Database.
* utime: (libc)File Times.
* utimensat: (libc)File Times.
* utimes: (libc)File Times.
* utmpname: (libc)Manipulating the Database.
* utmpxname: (libc)XPG Functions.
* va_arg: (libc)Argument Macros.
* va_copy: (libc)Argument Macros.
* va_end: (libc)Argument Macros.
* va_start: (libc)Argument Macros.
* valloc: (libc)Aligned Memory Blocks.
* vasprintf: (libc)Variable Arguments Output.
* vdprintf: (libc)Variable Arguments Output.
* verr: (libc)Error Messages.
* verrx: (libc)Error Messages.
* versionsort64: (libc)Scanning Directory Content.
* versionsort: (libc)Scanning Directory Content.
* vfork: (libc)Creating a Process.
* vfprintf: (libc)Variable Arguments Output.
* vfscanf: (libc)Variable Arguments Input.
* vfwprintf: (libc)Variable Arguments Output.
* vfwscanf: (libc)Variable Arguments Input.
* vlimit: (libc)Limits on Resources.
* vprintf: (libc)Variable Arguments Output.
* vscanf: (libc)Variable Arguments Input.
* vsnprintf: (libc)Variable Arguments Output.
* vsprintf: (libc)Variable Arguments Output.
* vsscanf: (libc)Variable Arguments Input.
* vswprintf: (libc)Variable Arguments Output.
* vswscanf: (libc)Variable Arguments Input.
* vsyslog: (libc)syslog; vsyslog.
* vwarn: (libc)Error Messages.
* vwarnx: (libc)Error Messages.
* vwprintf: (libc)Variable Arguments Output.
* vwscanf: (libc)Variable Arguments Input.
* wait3: (libc)BSD Wait Functions.
* wait4: (libc)Process Completion.
* wait: (libc)Process Completion.
* waitpid: (libc)Process Completion.
* warn: (libc)Error Messages.
* warnx: (libc)Error Messages.
* wcpcpy: (libc)Copying Strings and Arrays.
* wcpncpy: (libc)Truncating Strings.
* wcrtomb: (libc)Converting a Character.
* wcscasecmp: (libc)String/Array Comparison.
* wcscat: (libc)Concatenating Strings.
* wcschr: (libc)Search Functions.
* wcschrnul: (libc)Search Functions.
* wcscmp: (libc)String/Array Comparison.
* wcscoll: (libc)Collation Functions.
* wcscpy: (libc)Copying Strings and Arrays.
* wcscspn: (libc)Search Functions.
* wcsdup: (libc)Copying Strings and Arrays.
* wcsftime: (libc)Formatting Calendar Time.
* wcslcat: (libc)Truncating Strings.
* wcslcpy: (libc)Truncating Strings.
* wcslen: (libc)String Length.
* wcsncasecmp: (libc)String/Array Comparison.
* wcsncat: (libc)Truncating Strings.
* wcsncmp: (libc)String/Array Comparison.
* wcsncpy: (libc)Truncating Strings.
* wcsnlen: (libc)String Length.
* wcsnrtombs: (libc)Converting Strings.
* wcspbrk: (libc)Search Functions.
* wcsrchr: (libc)Search Functions.
* wcsrtombs: (libc)Converting Strings.
* wcsspn: (libc)Search Functions.
* wcsstr: (libc)Search Functions.
* wcstod: (libc)Parsing of Floats.
* wcstof: (libc)Parsing of Floats.
* wcstofN: (libc)Parsing of Floats.
* wcstofNx: (libc)Parsing of Floats.
* wcstoimax: (libc)Parsing of Integers.
* wcstok: (libc)Finding Tokens in a String.
* wcstol: (libc)Parsing of Integers.
* wcstold: (libc)Parsing of Floats.
* wcstoll: (libc)Parsing of Integers.
* wcstombs: (libc)Non-reentrant String Conversion.
* wcstoq: (libc)Parsing of Integers.
* wcstoul: (libc)Parsing of Integers.
* wcstoull: (libc)Parsing of Integers.
* wcstoumax: (libc)Parsing of Integers.
* wcstouq: (libc)Parsing of Integers.
* wcswcs: (libc)Search Functions.
* wcsxfrm: (libc)Collation Functions.
* wctob: (libc)Converting a Character.
* wctomb: (libc)Non-reentrant Character Conversion.
* wctrans: (libc)Wide Character Case Conversion.
* wctype: (libc)Classification of Wide Characters.
* wmemchr: (libc)Search Functions.
* wmemcmp: (libc)String/Array Comparison.
* wmemcpy: (libc)Copying Strings and Arrays.
* wmemmove: (libc)Copying Strings and Arrays.
* wmempcpy: (libc)Copying Strings and Arrays.
* wmemset: (libc)Copying Strings and Arrays.
* wordexp: (libc)Calling Wordexp.
* wordfree: (libc)Calling Wordexp.
* wprintf: (libc)Formatted Output Functions.
* write: (libc)I/O Primitives.
* writev: (libc)Scatter-Gather.
* wscanf: (libc)Formatted Input Functions.
* y0: (libc)Special Functions.
* y0f: (libc)Special Functions.
* y0fN: (libc)Special Functions.
* y0fNx: (libc)Special Functions.
* y0l: (libc)Special Functions.
* y1: (libc)Special Functions.
* y1f: (libc)Special Functions.
* y1fN: (libc)Special Functions.
* y1fNx: (libc)Special Functions.
* y1l: (libc)Special Functions.
* yn: (libc)Special Functions.
* ynf: (libc)Special Functions.
* ynfN: (libc)Special Functions.
* ynfNx: (libc)Special Functions.
* ynl: (libc)Special Functions.
END-INFO-DIR-ENTRY


File: libc.info,  Node: Standard Locales,  Next: Locale Names,  Prev: Setting the Locale,  Up: Locales

7.5 Standard Locales
====================

The only locale names you can count on finding on all operating systems
are these three standard ones:

‘"C"’
     This is the standard C locale.  The attributes and behavior it
     provides are specified in the ISO C standard.  When your program
     starts up, it initially uses this locale by default.

‘"POSIX"’
     This is the standard POSIX locale.  Currently, it is an alias for
     the standard C locale.

‘""’
     The empty name says to select a locale based on environment
     variables.  *Note Locale Categories::.

   Defining and installing named locales is normally a responsibility of
the system administrator at your site (or the person who installed the
GNU C Library).  It is also possible for the user to create private
locales.  All this will be discussed later when describing the tool to
do so.

   If your program needs to use something other than the ‘C’ locale, it
will be more portable if you use whatever locale the user specifies with
the environment, rather than trying to specify some non-standard locale
explicitly by name.  Remember, different machines might have different
sets of locales installed.


File: libc.info,  Node: Locale Names,  Next: Locale Information,  Prev: Standard Locales,  Up: Locales

7.6 Locale Names
================

The following command prints a list of locales supported by the system:

       locale -a

   *Portability Note:* With the notable exception of the standard locale
names ‘C’ and ‘POSIX’, locale names are system-specific.

   Most locale names follow XPG syntax and consist of up to four parts:

     LANGUAGE[_TERRITORY[.CODESET]][@MODIFIER]

   Beside the first part, all of them are allowed to be missing.  If the
full specified locale is not found, less specific ones are looked for.
The various parts will be stripped off, in the following order:

  1. codeset
  2. normalized codeset
  3. territory
  4. modifier

   For example, the locale name ‘de_AT.iso885915@euro’ denotes a
German-language locale for use in Austria, using the ISO-8859-15
(Latin-9) character set, and with the Euro as the currency symbol.

   In addition to locale names which follow XPG syntax, systems may
provide aliases such as ‘german’.  Both categories of names must not
contain the slash character ‘/’.

   If the locale name starts with a slash ‘/’, it is treated as a path
relative to the configured locale directories; see ‘LOCPATH’ below.  The
specified path must not contain a component ‘..’, or the name is
invalid, and ‘setlocale’ will fail.

   *Portability Note:* POSIX suggests that if a locale name starts with
a slash ‘/’, it is resolved as an absolute path.  However, the GNU C
Library treats it as a relative path under the directories listed in
‘LOCPATH’ (or the default locale directory if ‘LOCPATH’ is unset).

   Locale names which are longer than an implementation-defined limit
are invalid and cause ‘setlocale’ to fail.

   As a special case, locale names used with ‘LC_ALL’ can combine
several locales, reflecting different locale settings for different
categories.  For example, you might want to use a U.S. locale with ISO
A4 paper format, so you set ‘LANG’ to ‘en_US.UTF-8’, and ‘LC_PAPER’ to
‘de_DE.UTF-8’.  In this case, the ‘LC_ALL’-style combined locale name is

     LC_CTYPE=en_US.UTF-8;LC_TIME=en_US.UTF-8;LC_PAPER=de_DE.UTF-8;...

   followed by other category settings not shown here.

   The path used for finding locale data can be set using the ‘LOCPATH’
environment variable.  This variable lists the directories in which to
search for locale definitions, separated by a colon ‘:’.

   The default path for finding locale data is system specific.  A
typical value for the ‘LOCPATH’ default is:

     /usr/share/locale

   The value of ‘LOCPATH’ is ignored by privileged programs for security
reasons, and only the default directory is used.


File: libc.info,  Node: Locale Information,  Next: Formatting Numbers,  Prev: Locale Names,  Up: Locales

7.7 Accessing Locale Information
================================

There are several ways to access locale information.  The simplest way
is to let the C library itself do the work.  Several of the functions in
this library implicitly access the locale data, and use what information
is provided by the currently selected locale.  This is how the locale
model is meant to work normally.

   As an example take the ‘strftime’ function, which is meant to nicely
format date and time information (*note Formatting Calendar Time::).
Part of the standard information contained in the ‘LC_TIME’ category is
the names of the months.  Instead of requiring the programmer to take
care of providing the translations the ‘strftime’ function does this all
by itself.  ‘%A’ in the format string is replaced by the appropriate
weekday name of the locale currently selected by ‘LC_TIME’.  This is an
easy example, and wherever possible functions do things automatically in
this way.

   But there are quite often situations when there is simply no function
to perform the task, or it is simply not possible to do the work
automatically.  For these cases it is necessary to access the
information in the locale directly.  To do this the C library provides
two functions: ‘localeconv’ and ‘nl_langinfo’.  The former is part of
ISO C and therefore portable, but has a brain-damaged interface.  The
second is part of the Unix interface and is portable in as far as the
system follows the Unix standards.

* Menu:

* The Lame Way to Locale Data::   ISO C's ‘localeconv’.
* The Elegant and Fast Way::      X/Open's ‘nl_langinfo’.


File: libc.info,  Node: The Lame Way to Locale Data,  Next: The Elegant and Fast Way,  Up: Locale Information

7.7.1 ‘localeconv’: It is portable but ...
------------------------------------------

Together with the ‘setlocale’ function the ISO C people invented the
‘localeconv’ function.  It is a masterpiece of poor design.  It is
expensive to use, not extensible, and not generally usable as it
provides access to only ‘LC_MONETARY’ and ‘LC_NUMERIC’ related
information.  Nevertheless, if it is applicable to a given situation it
should be used since it is very portable.  The function ‘strfmon’
formats monetary amounts according to the selected locale using this
information.

 -- Function: struct lconv * localeconv (void)

     Preliminary: | MT-Unsafe race:localeconv locale | AS-Unsafe |
     AC-Safe | *Note POSIX Safety Concepts::.

     The ‘localeconv’ function returns a pointer to a structure whose
     components contain information about how numeric and monetary
     values should be formatted in the current locale.

     You should not modify the structure or its contents.  The structure
     might be overwritten by subsequent calls to ‘localeconv’, or by
     calls to ‘setlocale’, but no other function in the library
     overwrites this value.

 -- Data Type: struct lconv

     ‘localeconv’'s return value is of this data type.  Its elements are
     described in the following subsections.

   If a member of the structure ‘struct lconv’ has type ‘char’, and the
value is ‘CHAR_MAX’, it means that the current locale has no value for
that parameter.

* Menu:

* General Numeric::             Parameters for formatting numbers and
                                 currency amounts.
* Currency Symbol::             How to print the symbol that identifies an
                                 amount of money (e.g. ‘$’).
* Sign of Money Amount::        How to print the (positive or negative) sign
                                 for a monetary amount, if one exists.


File: libc.info,  Node: General Numeric,  Next: Currency Symbol,  Up: The Lame Way to Locale Data

7.7.1.1 Generic Numeric Formatting Parameters
.............................................

These are the standard members of ‘struct lconv’; there may be others.

‘char *decimal_point’
‘char *mon_decimal_point’
     These are the decimal-point separators used in formatting
     non-monetary and monetary quantities, respectively.  In the ‘C’
     locale, the value of ‘decimal_point’ is ‘"."’, and the value of
     ‘mon_decimal_point’ is ‘""’.

‘char *thousands_sep’
‘char *mon_thousands_sep’
     These are the separators used to delimit groups of digits to the
     left of the decimal point in formatting non-monetary and monetary
     quantities, respectively.  In the ‘C’ locale, both members have a
     value of ‘""’ (the empty string).

‘char *grouping’
‘char *mon_grouping’
     These are strings that specify how to group the digits to the left
     of the decimal point.  ‘grouping’ applies to non-monetary
     quantities and ‘mon_grouping’ applies to monetary quantities.  Use
     either ‘thousands_sep’ or ‘mon_thousands_sep’ to separate the digit
     groups.

     Each member of these strings is to be interpreted as an integer
     value of type ‘char’.  Successive numbers (from left to right) give
     the sizes of successive groups (from right to left, starting at the
     decimal point.)  The last member is either ‘0’, in which case the
     previous member is used over and over again for all the remaining
     groups, or ‘CHAR_MAX’, in which case there is no more grouping--or,
     put another way, any remaining digits form one large group without
     separators.

     For example, if ‘grouping’ is ‘"\04\03\02"’, the correct grouping
     for the number ‘123456787654321’ is ‘12’, ‘34’, ‘56’, ‘78’, ‘765’,
     ‘4321’.  This uses a group of 4 digits at the end, preceded by a
     group of 3 digits, preceded by groups of 2 digits (as many as
     needed).  With a separator of ‘,’, the number would be printed as
     ‘12,34,56,78,765,4321’.

     A value of ‘"\03"’ indicates repeated groups of three digits, as
     normally used in the U.S.

     In the standard ‘C’ locale, both ‘grouping’ and ‘mon_grouping’ have
     a value of ‘""’.  This value specifies no grouping at all.

‘char int_frac_digits’
‘char frac_digits’
     These are small integers indicating how many fractional digits (to
     the right of the decimal point) should be displayed in a monetary
     value in international and local formats, respectively.  (Most
     often, both members have the same value.)

     In the standard ‘C’ locale, both of these members have the value
     ‘CHAR_MAX’, meaning "unspecified".  The ISO standard doesn't say
     what to do when you find this value; we recommend printing no
     fractional digits.  (This locale also specifies the empty string
     for ‘mon_decimal_point’, so printing any fractional digits would be
     confusing!)


File: libc.info,  Node: Currency Symbol,  Next: Sign of Money Amount,  Prev: General Numeric,  Up: The Lame Way to Locale Data

7.7.1.2 Printing the Currency Symbol
....................................

These members of the ‘struct lconv’ structure specify how to print the
symbol to identify a monetary value--the international analog of ‘$’ for
US dollars.

   Each country has two standard currency symbols.  The “local currency
symbol” is used commonly within the country, while the “international
currency symbol” is used internationally to refer to that country's
currency when it is necessary to indicate the country unambiguously.

   For example, many countries use the dollar as their monetary unit,
and when dealing with international currencies it's important to specify
that one is dealing with (say) Canadian dollars instead of U.S. dollars
or Australian dollars.  But when the context is known to be Canada,
there is no need to make this explicit--dollar amounts are implicitly
assumed to be in Canadian dollars.

‘char *currency_symbol’
     The local currency symbol for the selected locale.

     In the standard ‘C’ locale, this member has a value of ‘""’ (the
     empty string), meaning "unspecified".  The ISO standard doesn't say
     what to do when you find this value; we recommend you simply print
     the empty string as you would print any other string pointed to by
     this variable.

‘char *int_curr_symbol’
     The international currency symbol for the selected locale.

     The value of ‘int_curr_symbol’ should normally consist of a
     three-letter abbreviation determined by the international standard
     ‘ISO 4217 Codes for the Representation of Currency and Funds’,
     followed by a one-character separator (often a space).

     In the standard ‘C’ locale, this member has a value of ‘""’ (the
     empty string), meaning "unspecified".  We recommend you simply
     print the empty string as you would print any other string pointed
     to by this variable.

‘char p_cs_precedes’
‘char n_cs_precedes’
‘char int_p_cs_precedes’
‘char int_n_cs_precedes’
     These members are ‘1’ if the ‘currency_symbol’ or ‘int_curr_symbol’
     strings should precede the value of a monetary amount, or ‘0’ if
     the strings should follow the value.  The ‘p_cs_precedes’ and
     ‘int_p_cs_precedes’ members apply to positive amounts (or zero),
     and the ‘n_cs_precedes’ and ‘int_n_cs_precedes’ members apply to
     negative amounts.

     In the standard ‘C’ locale, all of these members have a value of
     ‘CHAR_MAX’, meaning "unspecified".  The ISO standard doesn't say
     what to do when you find this value.  We recommend printing the
     currency symbol before the amount, which is right for most
     countries.  In other words, treat all nonzero values alike in these
     members.

     The members with the ‘int_’ prefix apply to the ‘int_curr_symbol’
     while the other two apply to ‘currency_symbol’.

‘char p_sep_by_space’
‘char n_sep_by_space’
‘char int_p_sep_by_space’
‘char int_n_sep_by_space’
     These members are ‘1’ if a space should appear between the
     ‘currency_symbol’ or ‘int_curr_symbol’ strings and the amount, or
     ‘0’ if no space should appear.  The ‘p_sep_by_space’ and
     ‘int_p_sep_by_space’ members apply to positive amounts (or zero),
     and the ‘n_sep_by_space’ and ‘int_n_sep_by_space’ members apply to
     negative amounts.

     In the standard ‘C’ locale, all of these members have a value of
     ‘CHAR_MAX’, meaning "unspecified".  The ISO standard doesn't say
     what you should do when you find this value; we suggest you treat
     it as 1 (print a space).  In other words, treat all nonzero values
     alike in these members.

     The members with the ‘int_’ prefix apply to the ‘int_curr_symbol’
     while the other two apply to ‘currency_symbol’.  There is one
     specialty with the ‘int_curr_symbol’, though.  Since all legal
     values contain a space at the end of the string one either prints
     this space (if the currency symbol must appear in front and must be
     separated) or one has to avoid printing this character at all
     (especially when at the end of the string).


File: libc.info,  Node: Sign of Money Amount,  Prev: Currency Symbol,  Up: The Lame Way to Locale Data

7.7.1.3 Printing the Sign of a Monetary Amount
..............................................

These members of the ‘struct lconv’ structure specify how to print the
sign (if any) of a monetary value.

‘char *positive_sign’
‘char *negative_sign’
     These are strings used to indicate positive (or zero) and negative
     monetary quantities, respectively.

     In the standard ‘C’ locale, both of these members have a value of
     ‘""’ (the empty string), meaning "unspecified".

     The ISO standard doesn't say what to do when you find this value;
     we recommend printing ‘positive_sign’ as you find it, even if it is
     empty.  For a negative value, print ‘negative_sign’ as you find it
     unless both it and ‘positive_sign’ are empty, in which case print
     ‘-’ instead.  (Failing to indicate the sign at all seems rather
     unreasonable.)

‘char p_sign_posn’
‘char n_sign_posn’
‘char int_p_sign_posn’
‘char int_n_sign_posn’
     These members are small integers that indicate how to position the
     sign for nonnegative and negative monetary quantities,
     respectively.  (The string used for the sign is what was specified
     with ‘positive_sign’ or ‘negative_sign’.)  The possible values are
     as follows:

     ‘0’
          The currency symbol and quantity should be surrounded by
          parentheses.

     ‘1’
          Print the sign string before the quantity and currency symbol.

     ‘2’
          Print the sign string after the quantity and currency symbol.

     ‘3’
          Print the sign string right before the currency symbol.

     ‘4’
          Print the sign string right after the currency symbol.

     ‘CHAR_MAX’
          "Unspecified".  Both members have this value in the standard
          ‘C’ locale.

     The ISO standard doesn't say what you should do when the value is
     ‘CHAR_MAX’.  We recommend you print the sign after the currency
     symbol.

     The members with the ‘int_’ prefix apply to the ‘int_curr_symbol’
     while the other two apply to ‘currency_symbol’.


File: libc.info,  Node: The Elegant and Fast Way,  Prev: The Lame Way to Locale Data,  Up: Locale Information

7.7.2 Pinpoint Access to Locale Data
------------------------------------

When writing the X/Open Portability Guide the authors realized that the
‘localeconv’ function is not enough to provide reasonable access to
locale information.  The information which was meant to be available in
the locale (as later specified in the POSIX.1 standard) requires more
ways to access it.  Therefore the ‘nl_langinfo’ function was introduced.

 -- Function: char * nl_langinfo (nl_item ITEM)

     Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | *Note POSIX
     Safety Concepts::.

     The ‘nl_langinfo’ function can be used to access individual
     elements of the locale categories.  Unlike the ‘localeconv’
     function, which returns all the information, ‘nl_langinfo’ lets the
     caller select what information it requires.  This is very fast and
     it is not a problem to call this function multiple times.

     A second advantage is that in addition to the numeric and monetary
     formatting information, information from the ‘LC_TIME’ and
     ‘LC_MESSAGES’ categories is available.

     The type ‘nl_item’ is defined in ‘nl_types.h’.  The argument ITEM
     is a numeric value defined in the header ‘langinfo.h’.  The X/Open
     standard defines the following values:

     ‘CODESET’
          ‘nl_langinfo’ returns a string with the name of the coded
          character set used in the selected locale.

     ‘ABDAY_1’
     ‘ABDAY_2’
     ‘ABDAY_3’
     ‘ABDAY_4’
     ‘ABDAY_5’
     ‘ABDAY_6’
     ‘ABDAY_7’
          ‘nl_langinfo’ returns the abbreviated weekday name.  ‘ABDAY_1’
          corresponds to Sunday.
     ‘DAY_1’
     ‘DAY_2’
     ‘DAY_3’
     ‘DAY_4’
     ‘DAY_5’
     ‘DAY_6’
     ‘DAY_7’
          Similar to ‘ABDAY_1’, etc., but here the return value is the
          unabbreviated weekday name.
     ‘ABMON_1’
     ‘ABMON_2’
     ‘ABMON_3’
     ‘ABMON_4’
     ‘ABMON_5’
     ‘ABMON_6’
     ‘ABMON_7’
     ‘ABMON_8’
     ‘ABMON_9’
     ‘ABMON_10’
     ‘ABMON_11’
     ‘ABMON_12’
          The return value is the abbreviated name of the month, in the
          grammatical form used when the month forms part of a complete
          date.  ‘ABMON_1’ corresponds to January.
     ‘MON_1’
     ‘MON_2’
     ‘MON_3’
     ‘MON_4’
     ‘MON_5’
     ‘MON_6’
     ‘MON_7’
     ‘MON_8’
     ‘MON_9’
     ‘MON_10’
     ‘MON_11’
     ‘MON_12’
          Similar to ‘ABMON_1’, etc., but here the month names are not
          abbreviated.  Here the first value ‘MON_1’ also corresponds to
          January.
     ‘ALTMON_1’
     ‘ALTMON_2’
     ‘ALTMON_3’
     ‘ALTMON_4’
     ‘ALTMON_5’
     ‘ALTMON_6’
     ‘ALTMON_7’
     ‘ALTMON_8’
     ‘ALTMON_9’
     ‘ALTMON_10’
     ‘ALTMON_11’
     ‘ALTMON_12’
          Similar to ‘MON_1’, etc., but here the month names are in the
          grammatical form used when the month is named by itself.  The
          ‘strftime’ functions use these month names for the conversion
          specifier ‘%OB’ (*note Formatting Calendar Time::).

          Note that not all languages need two different forms of the
          month names, so the strings returned for ‘MON_...’ and
          ‘ALTMON_...’ may or may not be the same, depending on the
          locale.

          *NB:* ‘ABALTMON_...’ constants corresponding to the ‘%Ob’
          conversion specifier are not currently provided, but are
          expected to be in a future release.  In the meantime, it is
          possible to use ‘_NL_ABALTMON_...’.
     ‘AM_STR’
     ‘PM_STR’
          The return values are strings which can be used in the
          representation of time as an hour from 1 to 12 plus an am/pm
          specifier.

          Note that in locales which do not use this time representation
          these strings might be empty, in which case the am/pm format
          cannot be used at all.
     ‘D_T_FMT’
          The return value can be used as a format string for ‘strftime’
          to represent time and date in a locale-specific way.
     ‘D_FMT’
          The return value can be used as a format string for ‘strftime’
          to represent a date in a locale-specific way.
     ‘T_FMT’
          The return value can be used as a format string for ‘strftime’
          to represent time in a locale-specific way.
     ‘T_FMT_AMPM’
          The return value can be used as a format string for ‘strftime’
          to represent time in the am/pm format.

          Note that if the am/pm format does not make any sense for the
          selected locale, the return value might be the same as the one
          for ‘T_FMT’.
     ‘ERA’
          The return value represents the era used in the current
          locale.

          Most locales do not define this value.  An example of a locale
          which does define this value is the Japanese one.  In Japan,
          the traditional representation of dates includes the name of
          the era corresponding to the then-emperor's reign.

          Normally it should not be necessary to use this value
          directly.  Specifying the ‘E’ modifier in their format strings
          causes the ‘strftime’ functions to use this information.  The
          format of the returned string is not specified, and therefore
          you should not assume knowledge of it on different systems.
     ‘ERA_YEAR’
          The return value gives the year in the relevant era of the
          locale.  As for ‘ERA’ it should not be necessary to use this
          value directly.
     ‘ERA_D_T_FMT’
          This return value can be used as a format string for
          ‘strftime’ to represent dates and times in a locale-specific
          era-based way.
     ‘ERA_D_FMT’
          This return value can be used as a format string for
          ‘strftime’ to represent a date in a locale-specific era-based
          way.
     ‘ERA_T_FMT’
          This return value can be used as a format string for
          ‘strftime’ to represent time in a locale-specific era-based
          way.
     ‘ALT_DIGITS’
          The return value is a representation of up to 100 values used
          to represent the values 0 to 99.  As for ‘ERA’ this value is
          not intended to be used directly, but instead indirectly
          through the ‘strftime’ function.  When the modifier ‘O’ is
          used in a format which would otherwise use numerals to
          represent hours, minutes, seconds, weekdays, months, or weeks,
          the appropriate value for the locale is used instead.
     ‘INT_CURR_SYMBOL’
          The same as the value returned by ‘localeconv’ in the
          ‘int_curr_symbol’ element of the ‘struct lconv’.
     ‘CURRENCY_SYMBOL’
     ‘CRNCYSTR’
          The same as the value returned by ‘localeconv’ in the
          ‘currency_symbol’ element of the ‘struct lconv’.

          ‘CRNCYSTR’ is a deprecated alias still required by Unix98.
     ‘MON_DECIMAL_POINT’
          The same as the value returned by ‘localeconv’ in the
          ‘mon_decimal_point’ element of the ‘struct lconv’.
     ‘MON_THOUSANDS_SEP’
          The same as the value returned by ‘localeconv’ in the
          ‘mon_thousands_sep’ element of the ‘struct lconv’.
     ‘MON_GROUPING’
          The same as the value returned by ‘localeconv’ in the
          ‘mon_grouping’ element of the ‘struct lconv’.
     ‘POSITIVE_SIGN’
          The same as the value returned by ‘localeconv’ in the
          ‘positive_sign’ element of the ‘struct lconv’.
     ‘NEGATIVE_SIGN’
          The same as the value returned by ‘localeconv’ in the
          ‘negative_sign’ element of the ‘struct lconv’.
     ‘INT_FRAC_DIGITS’
          The same as the value returned by ‘localeconv’ in the
          ‘int_frac_digits’ element of the ‘struct lconv’.
     ‘FRAC_DIGITS’
          The same as the value returned by ‘localeconv’ in the
          ‘frac_digits’ element of the ‘struct lconv’.
     ‘P_CS_PRECEDES’
          The same as the value returned by ‘localeconv’ in the
          ‘p_cs_precedes’ element of the ‘struct lconv’.
     ‘P_SEP_BY_SPACE’
          The same as the value returned by ‘localeconv’ in the
          ‘p_sep_by_space’ element of the ‘struct lconv’.
     ‘N_CS_PRECEDES’
          The same as the value returned by ‘localeconv’ in the
          ‘n_cs_precedes’ element of the ‘struct lconv’.
     ‘N_SEP_BY_SPACE’
          The same as the value returned by ‘localeconv’ in the
          ‘n_sep_by_space’ element of the ‘struct lconv’.
     ‘P_SIGN_POSN’
          The same as the value returned by ‘localeconv’ in the
          ‘p_sign_posn’ element of the ‘struct lconv’.
     ‘N_SIGN_POSN’
          The same as the value returned by ‘localeconv’ in the
          ‘n_sign_posn’ element of the ‘struct lconv’.

     ‘INT_P_CS_PRECEDES’
          The same as the value returned by ‘localeconv’ in the
          ‘int_p_cs_precedes’ element of the ‘struct lconv’.
     ‘INT_P_SEP_BY_SPACE’
          The same as the value returned by ‘localeconv’ in the
          ‘int_p_sep_by_space’ element of the ‘struct lconv’.
     ‘INT_N_CS_PRECEDES’
          The same as the value returned by ‘localeconv’ in the
          ‘int_n_cs_precedes’ element of the ‘struct lconv’.
     ‘INT_N_SEP_BY_SPACE’
          The same as the value returned by ‘localeconv’ in the
          ‘int_n_sep_by_space’ element of the ‘struct lconv’.
     ‘INT_P_SIGN_POSN’
          The same as the value returned by ‘localeconv’ in the
          ‘int_p_sign_posn’ element of the ‘struct lconv’.
     ‘INT_N_SIGN_POSN’
          The same as the value returned by ‘localeconv’ in the
          ‘int_n_sign_posn’ element of the ‘struct lconv’.

     ‘DECIMAL_POINT’
     ‘RADIXCHAR’
          The same as the value returned by ‘localeconv’ in the
          ‘decimal_point’ element of the ‘struct lconv’.

          The name ‘RADIXCHAR’ is a deprecated alias still used in
          Unix98.
     ‘THOUSANDS_SEP’
     ‘THOUSEP’
          The same as the value returned by ‘localeconv’ in the
          ‘thousands_sep’ element of the ‘struct lconv’.

          The name ‘THOUSEP’ is a deprecated alias still used in Unix98.
     ‘GROUPING’
          The same as the value returned by ‘localeconv’ in the
          ‘grouping’ element of the ‘struct lconv’.
     ‘YESEXPR’
          The return value is a regular expression which can be used
          with the ‘regex’ function to recognize a positive response to
          a yes/no question.  The GNU C Library provides the ‘rpmatch’
          function for easier handling in applications.
     ‘NOEXPR’
          The return value is a regular expression which can be used
          with the ‘regex’ function to recognize a negative response to
          a yes/no question.
     ‘YESSTR’
          The return value is a locale-specific translation of the
          positive response to a yes/no question.

          Using this value is deprecated since it is a very special case
          of message translation, and is better handled by the message
          translation functions (*note Message Translation::).

          The use of this symbol is deprecated.  Instead message
          translation should be used.
     ‘NOSTR’
          The return value is a locale-specific translation of the
          negative response to a yes/no question.  What is said for
          ‘YESSTR’ is also true here.

          The use of this symbol is deprecated.  Instead message
          translation should be used.

     The file ‘langinfo.h’ defines a lot more symbols but none of them
     are official.  Using them is not portable, and the format of the
     return values might change.  Therefore we recommended you not use
     them.

     Note that the return value for any valid argument can be used in
     all situations (with the possible exception of the am/pm time
     formatting codes).  If the user has not selected any locale for the
     appropriate category, ‘nl_langinfo’ returns the information from
     the ‘"C"’ locale.  It is therefore possible to use this function as
     shown in the example below.

     If the argument ITEM is not valid, a pointer to an empty string is
     returned.

   An example of ‘nl_langinfo’ usage is a function which has to print a
given date and time in a locale-specific way.  At first one might think
that, since ‘strftime’ internally uses the locale information, writing
something like the following is enough:

     size_t
     i18n_time_n_data (char *s, size_t len, const struct tm *tp)
     {
       return strftime (s, len, "%X %D", tp);
     }

   The format contains no weekday or month names and therefore is
internationally usable.  Wrong!  The output produced is something like
‘"hh:mm:ss MM/DD/YY"’.  This format is only recognizable in the USA.
Other countries use different formats.  Therefore the function should be
rewritten like this:

     size_t
     i18n_time_n_data (char *s, size_t len, const struct tm *tp)
     {
       return strftime (s, len, nl_langinfo (D_T_FMT), tp);
     }

   Now it uses the date and time format of the locale selected when the
program runs.  If the user selects the locale correctly there should
never be a misunderstanding over the time and date format.


File: libc.info,  Node: Formatting Numbers,  Next: Yes-or-No Questions,  Prev: Locale Information,  Up: Locales

7.8 A dedicated function to format numbers
==========================================

We have seen that the structure returned by ‘localeconv’ as well as the
values given to ‘nl_langinfo’ allow you to retrieve the various pieces
of locale-specific information to format numbers and monetary amounts.
We have also seen that the underlying rules are quite complex.

   Therefore the X/Open standards introduce a function which uses such
locale information, making it easier for the user to format numbers
according to these rules.

 -- Function: ssize_t strfmon (char *S, size_t MAXSIZE, const char
          *FORMAT, ...)
     Preliminary: | MT-Safe locale | AS-Unsafe heap | AC-Unsafe mem |
     *Note POSIX Safety Concepts::.

     The ‘strfmon’ function is similar to the ‘strftime’ function in
     that it takes a buffer, its size, a format string, and values to
     write into the buffer as text in a form specified by the format
     string.  Like ‘strftime’, the function also returns the number of
     bytes written into the buffer.

     There are two differences: ‘strfmon’ can take more than one
     argument, and, of course, the format specification is different.
     Like ‘strftime’, the format string consists of normal text, which
     is output as is, and format specifiers, which are indicated by a
     ‘%’.  Immediately after the ‘%’, you can optionally specify various
     flags and formatting information before the main formatting
     character, in a similar way to ‘printf’:

        • Immediately following the ‘%’ there can be one or more of the
          following flags:
          ‘=F’
               The single byte character F is used for this field as the
               numeric fill character.  By default this character is a
               space character.  Filling with this character is only
               performed if a left precision is specified.  It is not
               just to fill to the given field width.
          ‘^’
               The number is printed without grouping the digits
               according to the rules of the current locale.  By default
               grouping is enabled.
          ‘+’, ‘(’
               At most one of these flags can be used.  They select
               which format to represent the sign of a currency amount.
               By default, and if ‘+’ is given, the locale equivalent of
               +/- is used.  If ‘(’ is given, negative amounts are
               enclosed in parentheses.  The exact format is determined
               by the values of the ‘LC_MONETARY’ category of the locale
               selected at program runtime.
          ‘!’
               The output will not contain the currency symbol.
          ‘-’
               The output will be formatted left-justified instead of
               right-justified if it does not fill the entire field
               width.

     The next part of the specification is an optional field width.  If
     no width is specified 0 is taken.  During output, the function
     first determines how much space is required.  If it requires at
     least as many characters as given by the field width, it is output
     using as much space as necessary.  Otherwise, it is extended to use
     the full width by filling with the space character.  The presence
     or absence of the ‘-’ flag determines the side at which such
     padding occurs.  If present, the spaces are added at the right
     making the output left-justified, and vice versa.

     So far the format looks familiar, being similar to the ‘printf’ and
     ‘strftime’ formats.  However, the next two optional fields
     introduce something new.  The first one is a ‘#’ character followed
     by a decimal digit string.  The value of the digit string specifies
     the number of _digit_ positions to the left of the decimal point
     (or equivalent).  This does _not_ include the grouping character
     when the ‘^’ flag is not given.  If the space needed to print the
     number does not fill the whole width, the field is padded at the
     left side with the fill character, which can be selected using the
     ‘=’ flag and by default is a space.  For example, if the field
     width is selected as 6 and the number is 123, the fill character is
     ‘*’ the result will be ‘***123’.

     The second optional field starts with a ‘.’ (period) and consists
     of another decimal digit string.  Its value describes the number of
     characters printed after the decimal point.  The default is
     selected from the current locale (‘frac_digits’, ‘int_frac_digits’,
     see *note General Numeric::).  If the exact representation needs
     more digits than given by the field width, the displayed value is
     rounded.  If the number of fractional digits is selected to be
     zero, no decimal point is printed.

     As a GNU extension, the ‘strfmon’ implementation in the GNU C
     Library allows an optional ‘L’ next as a format modifier.  If this
     modifier is given, the argument is expected to be a ‘long double’
     instead of a ‘double’ value.

     Finally, the last component is a format specifier.  There are three
     specifiers defined:

     ‘i’
          Use the locale's rules for formatting an international
          currency value.
     ‘n’
          Use the locale's rules for formatting a national currency
          value.
     ‘%’
          Place a ‘%’ in the output.  There must be no flag, width
          specifier or modifier given, only ‘%%’ is allowed.

     As for ‘printf’, the function reads the format string from left to
     right and uses the values passed to the function following the
     format string.  The values are expected to be either of type
     ‘double’ or ‘long double’, depending on the presence of the
     modifier ‘L’.  The result is stored in the buffer pointed to by S.
     At most MAXSIZE characters are stored.

     The return value of the function is the number of characters stored
     in S, including the terminating ‘NULL’ byte.  If the number of
     characters stored would exceed MAXSIZE, the function returns -1 and
     the content of the buffer S is unspecified.  In this case ‘errno’
     is set to ‘E2BIG’.

   A few examples should make clear how the function works.  It is
assumed that all the following pieces of code are executed in a program
which uses the USA locale (‘en_US’).  The simplest form of the format is
this:

     strfmon (buf, 100, "@%n@%n@%n@", 123.45, -567.89, 12345.678);

The output produced is
     "@$123.45@-$567.89@$12,345.68@"

   We can notice several things here.  First, the widths of the output
numbers are different.  We have not specified a width in the format
string, and so this is no wonder.  Second, the third number is printed
using thousands separators.  The thousands separator for the ‘en_US’
locale is a comma.  The number is also rounded.  .678 is rounded to .68
since the format does not specify a precision and the default value in
the locale is 2.  Finally, note that the national currency symbol is
printed since ‘%n’ was used, not ‘i’.  The next example shows how we can
align the output.

     strfmon (buf, 100, "@%=*11n@%=*11n@%=*11n@", 123.45, -567.89, 12345.678);

The output this time is:

     "@    $123.45@   -$567.89@ $12,345.68@"

   Two things stand out.  Firstly, all fields have the same width
(eleven characters) since this is the width given in the format and
since no number required more characters to be printed.  The second
important point is that the fill character is not used.  This is correct
since the white space was not used to achieve a precision given by a ‘#’
modifier, but instead to fill to the given width.  The difference
becomes obvious if we now add a width specification.

     strfmon (buf, 100, "@%=*11#5n@%=*11#5n@%=*11#5n@",
              123.45, -567.89, 12345.678);

The output is

     "@ $***123.45@-$***567.89@ $12,456.68@"

   Here we can see that all the currency symbols are now aligned, and
that the space between the currency sign and the number is filled with
the selected fill character.  Note that although the width is selected
to be 5 and 123.45 has three digits left of the decimal point, the space
is filled with three asterisks.  This is correct since, as explained
above, the width does not include the positions used to store thousands
separators.  One last example should explain the remaining
functionality.

     strfmon (buf, 100, "@%=0(16#5.3i@%=0(16#5.3i@%=0(16#5.3i@",
              123.45, -567.89, 12345.678);

This rather complex format string produces the following output:

     "@ USD 000123,450 @(USD 000567.890)@ USD 12,345.678 @"

   The most noticeable change is the alternative way of representing
negative numbers.  In financial circles this is often done using
parentheses, and this is what the ‘(’ flag selected.  The fill character
is now ‘0’.  Note that this ‘0’ character is not regarded as a numeric
zero, and therefore the first and second numbers are not printed using a
thousands separator.  Since we used the format specifier ‘i’ instead of
‘n’, the international form of the currency symbol is used.  This is a
four letter string, in this case ‘"USD "’.  The last point is that since
the precision right of the decimal point is selected to be three, the
first and second numbers are printed with an extra zero at the end and
the third number is printed without rounding.


File: libc.info,  Node: Yes-or-No Questions,  Prev: Formatting Numbers,  Up: Locales

7.9 Yes-or-No Questions
=======================

Some non GUI programs ask a yes-or-no question.  If the messages
(especially the questions) are translated into foreign languages, be
sure that you localize the answers too.  It would be very bad habit to
ask a question in one language and request the answer in another, often
English.

   The GNU C Library contains ‘rpmatch’ to give applications easy access
to the corresponding locale definitions.

 -- Function: int rpmatch (const char *RESPONSE)

     Preliminary: | MT-Safe locale | AS-Unsafe corrupt heap lock dlopen
     | AC-Unsafe corrupt lock mem fd | *Note POSIX Safety Concepts::.

     The function ‘rpmatch’ checks the string in RESPONSE for whether or
     not it is a correct yes-or-no answer and if yes, which one.  The
     check uses the ‘YESEXPR’ and ‘NOEXPR’ data in the ‘LC_MESSAGES’
     category of the currently selected locale.  The return value is as
     follows:

     ‘1’
          The user entered an affirmative answer.

     ‘0’
          The user entered a negative answer.

     ‘-1’
          The answer matched neither the ‘YESEXPR’ nor the ‘NOEXPR’
          regular expression.

     This function is not standardized but available beside in the GNU C
     Library at least also in the IBM AIX library.

This function would normally be used like this:

       ...
       /* Use a safe default.  */
       _Bool doit = false;

       fputs (gettext ("Do you really want to do this? "), stdout);
       fflush (stdout);
       /* Prepare the ‘getline’ call.  */
       line = NULL;
       len = 0;
       while (getline (&line, &len, stdin) >= 0)
         {
           /* Check the response.  */
           int res = rpmatch (line);
           if (res >= 0)
             {
               /* We got a definitive answer.  */
               if (res > 0)
                 doit = true;
               break;
             }
         }
       /* Free what ‘getline’ allocated.  */
       free (line);

   Note that the loop continues until a read error is detected or until
a definitive (positive or negative) answer is read.


File: libc.info,  Node: Message Translation,  Next: Searching and Sorting,  Prev: Locales,  Up: Top

8 Message Translation
*********************

The program's interface with the user should be designed to ease the
user's task.  One way to ease the user's task is to use messages in
whatever language the user prefers.

   Printing messages in different languages can be implemented in
different ways.  One could add all the different languages in the source
code and choose among the variants every time a message has to be
printed.  This is certainly not a good solution since extending the set
of languages is cumbersome (the code must be changed) and the code
itself can become really big with dozens of message sets.

   A better solution is to keep the message sets for each language in
separate files which are loaded at runtime depending on the language
selection of the user.

   The GNU C Library provides two different sets of functions to support
message translation.  The ‘catgets’ family of functions were previously
the only family defined in the X/Open standard but they were derived
from industry decisions and therefore not necessarily based on
reasonable decisions.  However, the preferable ‘gettext’ family of
functions was standardized in POSIX-1.2024.

   As mentioned above, the message catalog handling provides easy
extendability by using external data files which contain the message
translations.  I.e., these files contain for each of the messages used
in the program a translation for the appropriate language.  So the tasks
of the message handling functions are

   • locate the external data file with the appropriate translations
   • load the data and make it possible to address the messages
   • map a given key to the translated message

   The two approaches mainly differ in the implementation of this last
step.  Decisions made in the last step influence the rest of the design.

* Menu:

* Message catalogs a la X/Open::  The ‘catgets’ family of functions.
* The Uniforum approach::         The ‘gettext’ family of functions.


File: libc.info,  Node: Message catalogs a la X/Open,  Next: The Uniforum approach,  Up: Message Translation

8.1 X/Open Message Catalog Handling
===================================

The ‘catgets’ functions are based on the simple scheme:

     Associate every message to translate in the source code with a
     unique identifier.  To retrieve a message from a catalog file
     solely the identifier is used.

   This means for the author of the program that s/he will have to make
sure the meaning of the identifier in the program code and in the
message catalogs is always the same.

   Before a message can be translated the catalog file must be located.
The user of the program must be able to guide the responsible function
to find whatever catalog the user wants.  This is separated from what
the programmer had in mind.

   All the types, constants and functions for the ‘catgets’ functions
are defined/declared in the ‘nl_types.h’ header file.

* Menu:

* The catgets Functions::      The ‘catgets’ function family.
* The message catalog files::  Format of the message catalog files.
* The gencat program::         How to generate message catalogs files which
                                can be used by the functions.
* Common Usage::               How to use the ‘catgets’ interface.


File: libc.info,  Node: The catgets Functions,  Next: The message catalog files,  Up: Message catalogs a la X/Open

8.1.1 The ‘catgets’ function family
-----------------------------------

 -- Function: nl_catd catopen (const char *CAT_NAME, int FLAG)

     Preliminary: | MT-Safe env | AS-Unsafe heap | AC-Unsafe mem | *Note
     POSIX Safety Concepts::.

     The ‘catopen’ function tries to locate the message data file named
     CAT_NAME and loads it when found.  The return value is of an opaque
     type and can be used in calls to the other functions to refer to
     this loaded catalog.

     The return value is ‘(nl_catd) -1’ in case the function failed and
     no catalog was loaded.  The global variable ‘errno’ contains a code
     for the error causing the failure.  But even if the function call
     succeeded this does not mean that all messages can be translated.

     Locating the catalog file must happen in a way which lets the user
     of the program influence the decision.  It is up to the user to
     decide about the language to use and sometimes it is useful to use
     alternate catalog files.  All this can be specified by the user by
     setting some environment variables.

     The first problem is to find out where all the message catalogs are
     stored.  Every program could have its own place to keep all the
     different files but usually the catalog files are grouped by
     languages and the catalogs for all programs are kept in the same
     place.

     To tell the ‘catopen’ function where the catalog for the program
     can be found the user can set the environment variable ‘NLSPATH’ to
     a value which describes her/his choice.  Since this value must be
     usable for different languages and locales it cannot be a simple
     string.  Instead it is a format string (similar to ‘printf’'s).  An
     example is

          /usr/share/locale/%L/%N:/usr/share/locale/%L/LC_MESSAGES/%N

     First one can see that more than one directory can be specified
     (with the usual syntax of separating them by colons).  The next
     things to observe are the format string, ‘%L’ and ‘%N’ in this
     case.  The ‘catopen’ function knows about several of them and the
     replacement for all of them is of course different.

     ‘%N’
          This format element is substituted with the name of the
          catalog file.  This is the value of the CAT_NAME argument
          given to ‘catgets’.

     ‘%L’
          This format element is substituted with the name of the
          currently selected locale for translating messages.  How this
          is determined is explained below.

     ‘%l’
          (This is the lowercase ell.)  This format element is
          substituted with the language element of the locale name.  The
          string describing the selected locale is expected to have the
          form ‘LANG[_TERR[.CODESET]]’ and this format uses the first
          part LANG.

     ‘%t’
          This format element is substituted by the territory part TERR
          of the name of the currently selected locale.  See the
          explanation of the format above.

     ‘%c’
          This format element is substituted by the codeset part CODESET
          of the name of the currently selected locale.  See the
          explanation of the format above.

     ‘%%’
          Since ‘%’ is used as a meta character there must be a way to
          express the ‘%’ character in the result itself.  Using ‘%%’
          does this just like it works for ‘printf’.

     Using ‘NLSPATH’ allows arbitrary directories to be searched for
     message catalogs while still allowing different languages to be
     used.  If the ‘NLSPATH’ environment variable is not set, the
     default value is

          PREFIX/share/locale/%L/%N:PREFIX/share/locale/%L/LC_MESSAGES/%N

     where PREFIX is given to ‘configure’ while installing the GNU C
     Library (this value is in many cases ‘/usr’ or the empty string).

     The remaining problem is to decide which must be used.  The value
     decides about the substitution of the format elements mentioned
     above.  First of all the user can specify a path in the message
     catalog name (i.e., the name contains a slash character).  In this
     situation the ‘NLSPATH’ environment variable is not used.  The
     catalog must exist as specified in the program, perhaps relative to
     the current working directory.  This situation in not desirable and
     catalogs names never should be written this way.  Beside this, this
     behavior is not portable to all other platforms providing the
     ‘catgets’ interface.

     Otherwise the values of environment variables from the standard
     environment are examined (*note Standard Environment::).  Which
     variables are examined is decided by the FLAG parameter of
     ‘catopen’.  If the value is ‘NL_CAT_LOCALE’ (which is defined in
     ‘nl_types.h’) then the ‘catopen’ function uses the name of the
     locale currently selected for the ‘LC_MESSAGES’ category.

     If FLAG is zero the ‘LANG’ environment variable is examined.  This
     is a left-over from the early days when the concept of locales had
     not even reached the level of POSIX locales.

     The environment variable and the locale name should have a value of
     the form ‘LANG[_TERR[.CODESET]]’ as explained above.  If no
     environment variable is set the ‘"C"’ locale is used which prevents
     any translation.

     The return value of the function is in any case a valid string.
     Either it is a translation from a message catalog or it is the same
     as the STRING parameter.  So a piece of code to decide whether a
     translation actually happened must look like this:

          {
            char *trans = catgets (desc, set, msg, input_string);
            if (trans == input_string)
              {
                /* Something went wrong.  */
              }
          }

     When an error occurs the global variable ‘errno’ is set to

     EBADF
          The catalog does not exist.
     ENOMSG
          The set/message tuple does not name an existing element in the
          message catalog.

     While it sometimes can be useful to test for errors programs
     normally will avoid any test.  If the translation is not available
     it is no big problem if the original, untranslated message is
     printed.  Either the user understands this as well or s/he will
     look for the reason why the messages are not translated.

   Please note that the currently selected locale does not depend on a
call to the ‘setlocale’ function.  It is not necessary that the locale
data files for this locale exist and calling ‘setlocale’ succeeds.  The
‘catopen’ function directly reads the values of the environment
variables.

 -- Function: char * catgets (nl_catd CATALOG_DESC, int SET, int
          MESSAGE, const char *STRING)
     Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
     Concepts::.

     The function ‘catgets’ has to be used to access the message catalog
     previously opened using the ‘catopen’ function.  The CATALOG_DESC
     parameter must be a value previously returned by ‘catopen’.

     The next two parameters, SET and MESSAGE, reflect the internal
     organization of the message catalog files.  This will be explained
     in detail below.  For now it is interesting to know that a catalog
     can consist of several sets and the messages in each thread are
     individually numbered using numbers.  Neither the set number nor
     the message number must be consecutive.  They can be arbitrarily
     chosen.  But each message (unless equal to another one) must have
     its own unique pair of set and message numbers.

     Since it is not guaranteed that the message catalog for the
     language selected by the user exists the last parameter STRING
     helps to handle this case gracefully.  If no matching string can be
     found STRING is returned.  This means for the programmer that

        • the STRING parameters should contain reasonable text (this
          also helps to understand the program seems otherwise there
          would be no hint on the string which is expected to be
          returned.
        • all STRING arguments should be written in the same language.

   It is somewhat uncomfortable to write a program using the ‘catgets’
functions if no supporting functionality is available.  Since each
set/message number tuple must be unique the programmer must keep lists
of the messages at the same time the code is written.  And the work
between several people working on the same project must be coordinated.
We will see how some of these problems can be relaxed a bit (*note
Common Usage::).

 -- Function: int catclose (nl_catd CATALOG_DESC)
     Preliminary: | MT-Safe | AS-Unsafe heap | AC-Unsafe corrupt mem |
     *Note POSIX Safety Concepts::.

     The ‘catclose’ function can be used to free the resources
     associated with a message catalog which previously was opened by a
     call to ‘catopen’.  If the resources can be successfully freed the
     function returns ‘0’.  Otherwise it returns ‘−1’ and the global
     variable ‘errno’ is set.  Errors can occur if the catalog
     descriptor CATALOG_DESC is not valid in which case ‘errno’ is set
     to ‘EBADF’.


File: libc.info,  Node: The message catalog files,  Next: The gencat program,  Prev: The catgets Functions,  Up: Message catalogs a la X/Open

8.1.2 Format of the message catalog files
-----------------------------------------

The only reasonable way to translate all the messages of a function and
store the result in a message catalog file which can be read by the
‘catopen’ function is to write all the message text to the translator
and let her/him translate them all.  I.e., we must have a file with
entries which associate the set/message tuple with a specific
translation.  This file format is specified in the X/Open standard and
is as follows:

   • Lines containing only whitespace characters or empty lines are
     ignored.

   • Lines which contain as the first non-whitespace character a ‘$’
     followed by a whitespace character are comment and are also
     ignored.

   • If a line contains as the first non-whitespace characters the
     sequence ‘$set’ followed by a whitespace character an additional
     argument is required to follow.  This argument can either be:

        − a number.  In this case the value of this number determines
          the set to which the following messages are added.

        − an identifier consisting of alphanumeric characters plus the
          underscore character.  In this case the set get automatically
          a number assigned.  This value is one added to the largest set
          number which so far appeared.

          How to use the symbolic names is explained in section *note
          Common Usage::.

          It is an error if a symbol name appears more than once.  All
          following messages are placed in a set with this number.

   • If a line contains as the first non-whitespace characters the
     sequence ‘$delset’ followed by a whitespace character an additional
     argument is required to follow.  This argument can either be:

        − a number.  In this case the value of this number determines
          the set which will be deleted.

        − an identifier consisting of alphanumeric characters plus the
          underscore character.  This symbolic identifier must match a
          name for a set which previously was defined.  It is an error
          if the name is unknown.

     In both cases all messages in the specified set will be removed.
     They will not appear in the output.  But if this set is later again
     selected with a ‘$set’ command again messages could be added and
     these messages will appear in the output.

   • If a line contains after leading whitespaces the sequence ‘$quote’,
     the quoting character used for this input file is changed to the
     first non-whitespace character following ‘$quote’.  If no
     non-whitespace character is present before the line ends quoting is
     disabled.

     By default no quoting character is used.  In this mode strings are
     terminated with the first unescaped line break.  If there is a
     ‘$quote’ sequence present newline need not be escaped.  Instead a
     string is terminated with the first unescaped appearance of the
     quote character.

     A common usage of this feature would be to set the quote character
     to ‘"’.  Then any appearance of the ‘"’ in the strings must be
     escaped using the backslash (i.e., ‘\"’ must be written).

   • Any other line must start with a number or an alphanumeric
     identifier (with the underscore character included).  The following
     characters (starting after the first whitespace character) will
     form the string which gets associated with the currently selected
     set and the message number represented by the number and identifier
     respectively.

     If the start of the line is a number the message number is obvious.
     It is an error if the same message number already appeared for this
     set.

     If the leading token was an identifier the message number gets
     automatically assigned.  The value is the current maximum message
     number for this set plus one.  It is an error if the identifier was
     already used for a message in this set.  It is OK to reuse the
     identifier for a message in another thread.  How to use the
     symbolic identifiers will be explained below (*note Common
     Usage::).  There is one limitation with the identifier: it must not
     be ‘Set’.  The reason will be explained below.

     The text of the messages can contain escape characters.  The usual
     bunch of characters known from the ISO C language are recognized
     (‘\n’, ‘\t’, ‘\v’, ‘\b’, ‘\r’, ‘\f’, ‘\\’, and ‘\NNN’, where NNN is
     the octal coding of a character code).

   *Important:* The handling of identifiers instead of numbers for the
set and messages is a GNU extension.  Systems strictly following the
X/Open specification do not have this feature.  An example for a message
catalog file is this:

     $ This is a leading comment.
     $quote "

     $set SetOne
     1 Message with ID 1.
     two "   Message with ID \"two\", which gets the value 2 assigned"

     $set SetTwo
     $ Since the last set got the number 1 assigned this set has number 2.
     4000 "The numbers can be arbitrary, they need not start at one."

   This small example shows various aspects:
   • Lines 1 and 9 are comments since they start with ‘$’ followed by a
     whitespace.
   • The quoting character is set to ‘"’.  Otherwise the quotes in the
     message definition would have to be omitted and in this case the
     message with the identifier ‘two’ would lose its leading
     whitespace.
   • Mixing numbered messages with messages having symbolic names is no
     problem and the numbering happens automatically.

   While this file format is pretty easy it is not the best possible for
use in a running program.  The ‘catopen’ function would have to parse
the file and handle syntactic errors gracefully.  This is not so easy
and the whole process is pretty slow.  Therefore the ‘catgets’ functions
expect the data in another more compact and ready-to-use file format.
There is a special program ‘gencat’ which is explained in detail in the
next section.

   Files in this other format are not human readable.  To be easy to use
by programs it is a binary file.  But the format is byte order
independent so translation files can be shared by systems of arbitrary
architecture (as long as they use the GNU C Library).

   Details about the binary file format are not important to know since
these files are always created by the ‘gencat’ program.  The sources of
the GNU C Library also provide the sources for the ‘gencat’ program and
so the interested reader can look through these source files to learn
about the file format.


File: libc.info,  Node: The gencat program,  Next: Common Usage,  Prev: The message catalog files,  Up: Message catalogs a la X/Open

8.1.3 Generate Message Catalogs files
-------------------------------------

The ‘gencat’ program is specified in the X/Open standard and the GNU
implementation follows this specification and so processes all correctly
formed input files.  Additionally some extension are implemented which
help to work in a more reasonable way with the ‘catgets’ functions.

   The ‘gencat’ program can be invoked in two ways:

     `gencat [OPTION ...] [OUTPUT-FILE [INPUT-FILE ...]]`

   This is the interface defined in the X/Open standard.  If no
INPUT-FILE parameter is given, input will be read from standard input.
Multiple input files will be read as if they were concatenated.  If
OUTPUT-FILE is also missing, the output will be written to standard
output.  To provide the interface one is used to from other programs a
second interface is provided.

     `gencat [OPTION ...] -o OUTPUT-FILE [INPUT-FILE ...]`

   The option ‘-o’ is used to specify the output file and all file
arguments are used as input files.

   Beside this one can use ‘-’ or ‘/dev/stdin’ for INPUT-FILE to denote
the standard input.  Corresponding one can use ‘-’ and ‘/dev/stdout’ for
OUTPUT-FILE to denote standard output.  Using ‘-’ as a file name is
allowed in X/Open while using the device names is a GNU extension.

   The ‘gencat’ program works by concatenating all input files and then
*merging* the resulting collection of message sets with a possibly
existing output file.  This is done by removing all messages with
set/message number tuples matching any of the generated messages from
the output file and then adding all the new messages.  To regenerate a
catalog file while ignoring the old contents therefore requires removing
the output file if it exists.  If the output is written to standard
output no merging takes place.

The following table shows the options understood by the ‘gencat’
program.  The X/Open standard does not specify any options for the
program so all of these are GNU extensions.

‘-V’
‘--version’
     Print the version information and exit.
‘-h’
‘--help’
     Print a usage message listing all available options, then exit
     successfully.
‘--new’
     Do not merge the new messages from the input files with the old
     content of the output file.  The old content of the output file is
     discarded.
‘-H’
‘--header=name’
     This option is used to emit the symbolic names given to sets and
     messages in the input files for use in the program.  Details about
     how to use this are given in the next section.  The NAME parameter
     to this option specifies the name of the output file.  It will
     contain a number of C preprocessor ‘#define’s to associate a name
     with a number.

     Please note that the generated file only contains the symbols from
     the input files.  If the output is merged with the previous content
     of the output file the possibly existing symbols from the file(s)
     which generated the old output files are not in the generated
     header file.


File: libc.info,  Node: Common Usage,  Prev: The gencat program,  Up: Message catalogs a la X/Open

8.1.4 How to use the ‘catgets’ interface
----------------------------------------

The ‘catgets’ functions can be used in two different ways.  By following
slavishly the X/Open specs and not relying on the extension and by using
the GNU extensions.  We will take a look at the former method first to
understand the benefits of extensions.

8.1.4.1 Not using symbolic names
................................

Since the X/Open format of the message catalog files does not allow
symbol names we have to work with numbers all the time.  When we start
writing a program we have to replace all appearances of translatable
strings with something like

     catgets (catdesc, set, msg, "string")

CATGETS is retrieved from a call to ‘catopen’ which is normally done
once at the program start.  The ‘"string"’ is the string we want to
translate.  The problems start with the set and message numbers.

   In a bigger program several programmers usually work at the same time
on the program and so coordinating the number allocation is crucial.
Though no two different strings must be indexed by the same tuple of
numbers it is highly desirable to reuse the numbers for equal strings
with equal translations (please note that there might be strings which
are equal in one language but have different translations due to
difference contexts).

   The allocation process can be relaxed a bit by different set numbers
for different parts of the program.  So the number of developers who
have to coordinate the allocation can be reduced.  But still lists must
be keep track of the allocation and errors can easily happen.  These
errors cannot be discovered by the compiler or the ‘catgets’ functions.
Only the user of the program might see wrong messages printed.  In the
worst cases the messages are so irritating that they cannot be
recognized as wrong.  Think about the translations for ‘"true"’ and
‘"false"’ being exchanged.  This could result in a disaster.

8.1.4.2 Using symbolic names
............................

The problems mentioned in the last section derive from the fact that:

  1. the numbers are allocated once and due to the possibly frequent use
     of them it is difficult to change a number later.
  2. the numbers do not allow guessing anything about the string and
     therefore collisions can easily happen.

   By constantly using symbolic names and by providing a method which
maps the string content to a symbolic name (however this will happen)
one can prevent both problems above.  The cost of this is that the
programmer has to write a complete message catalog file while s/he is
writing the program itself.

   This is necessary since the symbolic names must be mapped to numbers
before the program sources can be compiled.  In the last section it was
described how to generate a header containing the mapping of the names.
E.g., for the example message file given in the last section we could
call the ‘gencat’ program as follows (assume ‘ex.msg’ contains the
sources).

     gencat -H ex.h -o ex.cat ex.msg

This generates a header file with the following content:

     #define SetTwoSet 0x2   /* ex.msg:8 */

     #define SetOneSet 0x1   /* ex.msg:4 */
     #define SetOnetwo 0x2   /* ex.msg:6 */

   As can be seen the various symbols given in the source file are
mangled to generate unique identifiers and these identifiers get numbers
assigned.  Reading the source file and knowing about the rules will
allow to predict the content of the header file (it is deterministic)
but this is not necessary.  The ‘gencat’ program can take care for
everything.  All the programmer has to do is to put the generated header
file in the dependency list of the source files of her/his project and
add a rule to regenerate the header if any of the input files change.

   One word about the symbol mangling.  Every symbol consists of two
parts: the name of the message set plus the name of the message or the
special string ‘Set’.  So ‘SetOnetwo’ means this macro can be used to
access the translation with identifier ‘two’ in the message set
‘SetOne’.

   The other names denote the names of the message sets.  The special
string ‘Set’ is used in the place of the message identifier.

   If in the code the second string of the set ‘SetOne’ is used the C
code should look like this:

     catgets (catdesc, SetOneSet, SetOnetwo,
              "   Message with ID \"two\", which gets the value 2 assigned")

   Writing the function this way will allow to change the message number
and even the set number without requiring any change in the C source
code.  (The text of the string is normally not the same; this is only
for this example.)

8.1.4.3 How does to this allow to develop
.........................................

To illustrate the usual way to work with the symbolic version numbers
here is a little example.  Assume we want to write the very complex and
famous greeting program.  We start by writing the code as usual:

     #include <stdio.h>
     int
     main (void)
     {
       printf ("Hello, world!\n");
       return 0;
     }

   Now we want to internationalize the message and therefore replace the
message with whatever the user wants.

     #include <nl_types.h>
     #include <stdio.h>
     #include "msgnrs.h"
     int
     main (void)
     {
       nl_catd catdesc = catopen ("hello.cat", NL_CAT_LOCALE);
       printf (catgets (catdesc, SetMainSet, SetMainHello,
                        "Hello, world!\n"));
       catclose (catdesc);
       return 0;
     }

   We see how the catalog object is opened and the returned descriptor
used in the other function calls.  It is not really necessary to check
for failure of any of the functions since even in these situations the
functions will behave reasonable.  They simply will be return a
translation.

   What remains unspecified here are the constants ‘SetMainSet’ and
‘SetMainHello’.  These are the symbolic names describing the message.
To get the actual definitions which match the information in the catalog
file we have to create the message catalog source file and process it
using the ‘gencat’ program.

     $ Messages for the famous greeting program.
     $quote "

     $set Main
     Hello "Hallo, Welt!\n"

   Now we can start building the program (assume the message catalog
source file is named ‘hello.msg’ and the program source file ‘hello.c’):

     % gencat -H msgnrs.h -o hello.cat hello.msg
     % cat msgnrs.h
     #define MainSet 0x1     /* hello.msg:4 */
     #define MainHello 0x1   /* hello.msg:5 */
     % gcc -o hello hello.c -I.
     % cp hello.cat /usr/share/locale/de/LC_MESSAGES
     % echo $LC_ALL
     de
     % ./hello
     Hallo, Welt!
     %

   The call of the ‘gencat’ program creates the missing header file
‘msgnrs.h’ as well as the message catalog binary.  The former is used in
the compilation of ‘hello.c’ while the later is placed in a directory in
which the ‘catopen’ function will try to locate it.  Please check the
‘LC_ALL’ environment variable and the default path for ‘catopen’
presented in the description above.


File: libc.info,  Node: The Uniforum approach,  Prev: Message catalogs a la X/Open,  Up: Message Translation

8.2 The Uniforum approach to Message Translation
================================================

Sun Microsystems tried to standardize a different approach to message
translation in the Uniforum group.  There never was a real standard
defined but still the interface was used in Sun's operating systems.
Since this approach fits better in the development process of free
software it is also used throughout the GNU project and the GNU
‘gettext’ package provides support for this outside the GNU C Library.

   The code of the ‘libintl’ from GNU ‘gettext’ is the same as the code
in the GNU C Library.  So the documentation in the GNU ‘gettext’ manual
is also valid for the functionality here.  The following text will
describe the library functions in detail.  But the numerous helper
programs are not described in this manual.  Instead people should read
the GNU ‘gettext’ manual (*note GNU gettext utilities: (gettext)Top.).
We will only give a short overview.

   Though the ‘catgets’ functions are available by default on more
systems the ‘gettext’ interface is at least as portable as the former.
The GNU ‘gettext’ package can be used wherever the functions are not
available.

* Menu:

* Message catalogs with gettext::  The ‘gettext’ family of functions.
* Helper programs for gettext::    Programs to handle message catalogs
                                    for ‘gettext’.


File: libc.info,  Node: Message catalogs with gettext,  Next: Helper programs for gettext,  Up: The Uniforum approach

8.2.1 The ‘gettext’ family of functions
---------------------------------------

The paradigms underlying the ‘gettext’ approach to message translations
is different from that of the ‘catgets’ functions the basic functionally
is equivalent.  There are functions of the following categories:

* Menu:

* Translation with gettext::       What has to be done to translate a message.
* Locating gettext catalog::       How to determine which catalog to be used.
* Advanced gettext functions::     Additional functions for more complicated
                                    situations.
* Charset conversion in gettext::  How to specify the output character set
                                    ‘gettext’ uses.
* GUI program problems::           How to use ‘gettext’ in GUI programs.
* Using gettextized software::     The possibilities of the user to influence
                                    the way ‘gettext’ works.


File: libc.info,  Node: Translation with gettext,  Next: Locating gettext catalog,  Up: Message catalogs with gettext

8.2.1.1 What has to be done to translate a message?
...................................................

The ‘gettext’ functions have a very simple interface.  The most basic
function just takes the string which shall be translated as the argument
and it returns the translation.  This is fundamentally different from
the ‘catgets’ approach where an extra key is necessary and the original
string is only used for the error case.

   If the string which has to be translated is the only argument this of
course means the string itself is the key.  I.e., the translation will
be selected based on the original string.  The message catalogs must
therefore contain the original strings plus one translation for any such
string.  The task of the ‘gettext’ function is to compare the argument
string with the available strings in the catalog and return the
appropriate translation.  Of course this process is optimized so that
this process is not more expensive than an access using an atomic key
like in ‘catgets’.

   The ‘gettext’ approach has some advantages but also some
disadvantages.  Please see the GNU ‘gettext’ manual for a detailed
discussion of the pros and cons.

   All the definitions and declarations for ‘gettext’ can be found in
the ‘libintl.h’ header file.  On systems where these functions are not
part of the C library they can be found in a separate library named
‘libintl.a’ (or accordingly different for shared libraries).

 -- Function: char * gettext (const char *MSGID)

     Preliminary: | MT-Safe env | AS-Unsafe corrupt heap lock dlopen |
     AC-Unsafe corrupt lock fd mem | *Note POSIX Safety Concepts::.

     The ‘gettext’ function searches the currently selected message
     catalogs for a string which is equal to MSGID.  If there is such a
     string available it is returned.  Otherwise the argument string
     MSGID is returned.

     Please note that although the return value is ‘char *’ the returned
     string must not be changed.  This broken type results from the
     history of the function and does not reflect the way the function
     should be used.

     Please note that above we wrote "message catalogs" (plural).  This
     is a specialty of the GNU implementation of these functions and we
     will say more about this when we talk about the ways message
     catalogs are selected (*note Locating gettext catalog::).

     The ‘gettext’ function does not modify the value of the global
     ‘errno’ variable.  This is necessary to make it possible to write
     something like

            printf (gettext ("Operation failed: %m\n"));

     Here the ‘errno’ value is used in the ‘printf’ function while
     processing the ‘%m’ format element and if the ‘gettext’ function
     would change this value (it is called before ‘printf’ is called) we
     would get a wrong message.

     So there is no easy way to detect a missing message catalog besides
     comparing the argument string with the result.  But it is normally
     the task of the user to react on missing catalogs.  The program
     cannot guess when a message catalog is really necessary since for a
     user who speaks the language the program was developed in, the
     message does not need any translation.

   The remaining two functions to access the message catalog add some
functionality to select a message catalog which is not the default one.
This is important if parts of the program are developed independently.
Every part can have its own message catalog and all of them can be used
at the same time.  The C library itself is an example: internally it
uses the ‘gettext’ functions but since it must not depend on a currently
selected default message catalog it must specify all ambiguous
information.

 -- Function: char * dgettext (const char *DOMAINNAME, const char
          *MSGID)

     Preliminary: | MT-Safe env | AS-Unsafe corrupt heap lock dlopen |
     AC-Unsafe corrupt lock fd mem | *Note POSIX Safety Concepts::.

     The ‘dgettext’ function acts just like the ‘gettext’ function.  It
     only takes an additional first argument DOMAINNAME which guides the
     selection of the message catalogs which are searched for the
     translation.  If the DOMAINNAME parameter is the null pointer the
     ‘dgettext’ function is exactly equivalent to ‘gettext’ since the
     default value for the domain name is used.

     As for ‘gettext’ the return value type is ‘char *’ which is an
     anachronism.  The returned string must never be modified.

 -- Function: char * dcgettext (const char *DOMAINNAME, const char
          *MSGID, int CATEGORY)

     Preliminary: | MT-Safe env | AS-Unsafe corrupt heap lock dlopen |
     AC-Unsafe corrupt lock fd mem | *Note POSIX Safety Concepts::.

     The ‘dcgettext’ adds another argument to those which ‘dgettext’
     takes.  This argument CATEGORY specifies the last piece of
     information needed to localize the message catalog.  I.e., the
     domain name and the locale category exactly specify which message
     catalog has to be used (relative to a given directory, see below).

     The ‘dgettext’ function can be expressed in terms of ‘dcgettext’ by
     using

          dcgettext (domain, string, LC_MESSAGES)

     instead of

          dgettext (domain, string)

     This also shows which values are expected for the third parameter.
     One has to use the available selectors for the categories available
     in ‘locale.h’.  Normally the available values are ‘LC_CTYPE’,
     ‘LC_COLLATE’, ‘LC_MESSAGES’, ‘LC_MONETARY’, ‘LC_NUMERIC’, and
     ‘LC_TIME’.  Please note that ‘LC_ALL’ must not be used and even
     though the names might suggest this, there is no relation to the
     environment variable of this name.

     The ‘dcgettext’ function is only implemented for compatibility with
     other systems which have ‘gettext’ functions.  There is not really
     any situation where it is necessary (or useful) to use a different
     value than ‘LC_MESSAGES’ for the CATEGORY parameter.  We are
     dealing with messages here and any other choice can only be
     irritating.

     As for ‘gettext’ the return value type is ‘char *’ which is an
     anachronism.  The returned string must never be modified.

   When using the three functions above in a program it is a frequent
case that the MSGID argument is a constant string.  So it is worthwhile
to optimize this case.  Thinking shortly about this one will realize
that as long as no new message catalog is loaded the translation of a
message will not change.  This optimization is actually implemented by
the ‘gettext’, ‘dgettext’ and ‘dcgettext’ functions.


File: libc.info,  Node: Locating gettext catalog,  Next: Advanced gettext functions,  Prev: Translation with gettext,  Up: Message catalogs with gettext

8.2.1.2 How to determine which catalog to be used
.................................................

The functions to retrieve the translations for a given message have a
remarkable simple interface.  But to provide the user of the program
still the opportunity to select exactly the translation s/he wants and
also to provide the programmer the possibility to influence the way to
locate the search for catalogs files there is a quite complicated
underlying mechanism which controls all this.  The code is complicated
the use is easy.

   Basically we have two different tasks to perform which can also be
performed by the ‘catgets’ functions:

  1. Locate the set of message catalogs.  There are a number of files
     for different languages which all belong to the package.  Usually
     they are all stored in the filesystem below a certain directory.

     There can be arbitrarily many packages installed and they can
     follow different guidelines for the placement of their files.

  2. Relative to the location specified by the package the actual
     translation files must be searched, based on the wishes of the
     user.  I.e., for each language the user selects the program should
     be able to locate the appropriate file.

   This is the functionality required by the specifications for
‘gettext’ and this is also what the ‘catgets’ functions are able to do.
But there are some problems unresolved:

   • The language to be used can be specified in several different ways.
     There is no generally accepted standard for this and the user
     always expects the program to understand what s/he means.  E.g., to
     select the German translation one could write ‘de’, ‘german’, or
     ‘deutsch’ and the program should always react the same.

   • Sometimes the specification of the user is too detailed.  If s/he,
     e.g., specifies ‘de_DE.ISO-8859-1’ which means German, spoken in
     Germany, coded using the ISO 8859-1 character set there is the
     possibility that a message catalog matching this exactly is not
     available.  But there could be a catalog matching ‘de’ and if the
     character set used on the machine is always ISO 8859-1 there is no
     reason why this later message catalog should not be used.  (We call
     this “message inheritance”.)

   • If a catalog for a wanted language is not available it is not
     always the second best choice to fall back on the language of the
     developer and simply not translate any message.  Instead a user
     might be better able to read the messages in another language and
     so the user of the program should be able to define a precedence
     order of languages.

   We can divide the configuration actions in two parts: the one is
performed by the programmer, the other by the user.  We will start with
the functions the programmer can use since the user configuration will
be based on this.

   As the functions described in the last sections already mention
separate sets of messages can be selected by a “domain name”.  This is a
simple string which should be unique for each program part that uses a
separate domain.  It is possible to use in one program arbitrarily many
domains at the same time.  E.g., the GNU C Library itself uses a domain
named ‘libc’ while the program using the C Library could use a domain
named ‘foo’.  The important point is that at any time exactly one domain
is active.  This is controlled with the following function.

 -- Function: char * textdomain (const char *DOMAINNAME)

     Preliminary: | MT-Safe | AS-Unsafe lock heap | AC-Unsafe lock mem |
     *Note POSIX Safety Concepts::.

     The ‘textdomain’ function sets the default domain, which is used in
     all future ‘gettext’ calls, to DOMAINNAME.  Please note that
     ‘dgettext’ and ‘dcgettext’ calls are not influenced if the
     DOMAINNAME parameter of these functions is not the null pointer.

     Before the first call to ‘textdomain’ the default domain is
     ‘messages’.  This is the name specified in the specification of the
     ‘gettext’ API. This name is as good as any other name.  No program
     should ever really use a domain with this name since this can only
     lead to problems.

     The function returns the value which is from now on taken as the
     default domain.  If the system went out of memory the returned
     value is ‘NULL’ and the global variable ‘errno’ is set to ‘ENOMEM’.
     Despite the return value type being ‘char *’ the return string must
     not be changed.  It is allocated internally by the ‘textdomain’
     function.

     If the DOMAINNAME parameter is the null pointer no new default
     domain is set.  Instead the currently selected default domain is
     returned.

     If the DOMAINNAME parameter is the empty string the default domain
     is reset to its initial value, the domain with the name ‘messages’.
     This possibility is questionable to use since the domain ‘messages’
     really never should be used.

 -- Function: char * bindtextdomain (const char *DOMAINNAME, const char
          *DIRNAME)

     Preliminary: | MT-Safe | AS-Unsafe heap | AC-Unsafe mem | *Note
     POSIX Safety Concepts::.

     The ‘bindtextdomain’ function can be used to specify the directory
     which contains the message catalogs for domain DOMAINNAME for the
     different languages.  To be correct, this is the directory where
     the hierarchy of directories is expected.  Details are explained
     below.

     For the programmer it is important to note that the translations
     which come with the program have to be placed in a directory
     hierarchy starting at, say, ‘/foo/bar’.  Then the program should
     make a ‘bindtextdomain’ call to bind the domain for the current
     program to this directory.  So it is made sure the catalogs are
     found.  A correctly running program does not depend on the user
     setting an environment variable.

     The ‘bindtextdomain’ function can be used several times and if the
     DOMAINNAME argument is different the previously bound domains will
     not be overwritten.

     If the program which wish to use ‘bindtextdomain’ at some point of
     time use the ‘chdir’ function to change the current working
     directory it is important that the DIRNAME strings ought to be an
     absolute pathname.  Otherwise the addressed directory might vary
     with the time.

     If the DIRNAME parameter is the null pointer ‘bindtextdomain’
     returns the currently selected directory for the domain with the
     name DOMAINNAME.

     The ‘bindtextdomain’ function returns a pointer to a string
     containing the name of the selected directory name.  The string is
     allocated internally in the function and must not be changed by the
     user.  If the system went out of core during the execution of
     ‘bindtextdomain’ the return value is ‘NULL’ and the global variable
     ‘errno’ is set accordingly.


File: libc.info,  Node: Advanced gettext functions,  Next: Charset conversion in gettext,  Prev: Locating gettext catalog,  Up: Message catalogs with gettext

8.2.1.3 Additional functions for more complicated situations
............................................................

The functions of the ‘gettext’ family described so far (and all the
‘catgets’ functions as well) have one problem in the real world which
has been neglected completely in all existing approaches.  What is meant
here is the handling of plural forms.

   Looking through Unix source code before the time anybody thought
about internationalization (and, sadly, even afterwards) one can often
find code similar to the following:

        printf ("%d file%s deleted", n, n == 1 ? "" : "s");

After the first complaints from people internationalizing the code
people either completely avoided formulations like this or used strings
like ‘"file(s)"’.  Both look unnatural and should be avoided.  First
tries to solve the problem correctly looked like this:

        if (n == 1)
          printf ("%d file deleted", n);
        else
          printf ("%d files deleted", n);

   But this does not solve the problem.  It helps languages where the
plural form of a noun is not simply constructed by adding an 's' but
that is all.  Once again people fell into the trap of believing the
rules their language uses are universal.  But the handling of plural
forms differs widely between the language families.  There are two
things we can differ between (and even inside language families);

   • The form how plural forms are build differs.  This is a problem
     with language which have many irregularities.  German, for
     instance, is a drastic case.  Though English and German are part of
     the same language family (Germanic), the almost regular forming of
     plural noun forms (appending an 's') is hardly found in German.

   • The number of plural forms differ.  This is somewhat surprising for
     those who only have experiences with Romanic and Germanic languages
     since here the number is the same (there are two).

     But other language families have only one form or many forms.  More
     information on this in an extra section.

   The consequence of this is that application writers should not try to
solve the problem in their code.  This would be localization since it is
only usable for certain, hardcoded language environments.  Instead the
extended ‘gettext’ interface should be used.

   These extra functions are taking instead of the one key string two
strings and a numerical argument.  The idea behind this is that using
the numerical argument and the first string as a key, the implementation
can select using rules specified by the translator the right plural
form.  The two string arguments then will be used to provide a return
value in case no message catalog is found (similar to the normal
‘gettext’ behavior).  In this case the rules for Germanic language are
used and it is assumed that the first string argument is the singular
form, the second the plural form.

   This has the consequence that programs without language catalogs can
display the correct strings only if the program itself is written using
a Germanic language.  This is a limitation but since the GNU C Library
(as well as the GNU ‘gettext’ package) is written as part of the GNU
package and the coding standards for the GNU project require programs to
be written in English, this solution nevertheless fulfills its purpose.

 -- Function: char * ngettext (const char *MSGID1, const char *MSGID2,
          unsigned long int N)

     Preliminary: | MT-Safe env | AS-Unsafe corrupt heap lock dlopen |
     AC-Unsafe corrupt lock fd mem | *Note POSIX Safety Concepts::.

     The ‘ngettext’ function is similar to the ‘gettext’ function as it
     finds the message catalogs in the same way.  But it takes two extra
     arguments.  The MSGID1 parameter must contain the singular form of
     the string to be converted.  It is also used as the key for the
     search in the catalog.  The MSGID2 parameter is the plural form.
     The parameter N is used to determine the plural form.  If no
     message catalog is found MSGID1 is returned if ‘n == 1’, otherwise
     ‘msgid2’.

     An example for the use of this function is:

            printf (ngettext ("%d file removed", "%d files removed", n), n);

     Please note that the numeric value N has to be passed to the
     ‘printf’ function as well.  It is not sufficient to pass it only to
     ‘ngettext’.

 -- Function: char * dngettext (const char *DOMAIN, const char *MSGID1,
          const char *MSGID2, unsigned long int N)

     Preliminary: | MT-Safe env | AS-Unsafe corrupt heap lock dlopen |
     AC-Unsafe corrupt lock fd mem | *Note POSIX Safety Concepts::.

     The ‘dngettext’ is similar to the ‘dgettext’ function in the way
     the message catalog is selected.  The difference is that it takes
     two extra parameters to provide the correct plural form.  These two
     parameters are handled in the same way ‘ngettext’ handles them.

 -- Function: char * dcngettext (const char *DOMAIN, const char *MSGID1,
          const char *MSGID2, unsigned long int N, int CATEGORY)

     Preliminary: | MT-Safe env | AS-Unsafe corrupt heap lock dlopen |
     AC-Unsafe corrupt lock fd mem | *Note POSIX Safety Concepts::.

     The ‘dcngettext’ is similar to the ‘dcgettext’ function in the way
     the message catalog is selected.  The difference is that it takes
     two extra parameters to provide the correct plural form.  These two
     parameters are handled in the same way ‘ngettext’ handles them.

The problem of plural forms
...........................

A description of the problem can be found at the beginning of the last
section.  Now there is the question how to solve it.  Without the input
of linguists (which was not available) it was not possible to determine
whether there are only a few different forms in which plural forms are
formed or whether the number can increase with every new supported
language.

   Therefore the solution implemented is to allow the translator to
specify the rules of how to select the plural form.  Since the formula
varies with every language this is the only viable solution except for
hardcoding the information in the code (which still would require the
possibility of extensions to not prevent the use of new languages).  The
details are explained in the GNU ‘gettext’ manual.  Here only a bit of
information is provided.

   The information about the plural form selection has to be stored in
the header entry (the one with the empty ‘msgid’ string).  It looks like
this:

     Plural-Forms: nplurals=2; plural=n == 1 ? 0 : 1;

   The ‘nplurals’ value must be a decimal number which specifies how
many different plural forms exist for this language.  The string
following ‘plural’ is an expression using the C language syntax.
Exceptions are that no negative numbers are allowed, numbers must be
decimal, and the only variable allowed is ‘n’.  This expression will be
evaluated whenever one of the functions ‘ngettext’, ‘dngettext’, or
‘dcngettext’ is called.  The numeric value passed to these functions is
then substituted for all uses of the variable ‘n’ in the expression.
The resulting value then must be greater or equal to zero and smaller
than the value given as the value of ‘nplurals’.

The following rules are known at this point.  The language with families
are listed.  But this does not necessarily mean the information can be
generalized for the whole family (as can be easily seen in the table
below).(1)

Only one form:
     Some languages only require one single form.  There is no
     distinction between the singular and plural form.  An appropriate
     header entry would look like this:

          Plural-Forms: nplurals=1; plural=0;

     Languages with this property include:

     Finno-Ugric family
          Hungarian
     Asian family
          Japanese, Korean
     Turkic/Altaic family
          Turkish

Two forms, singular used for one only
     This is the form used in most existing programs since it is what
     English uses.  A header entry would look like this:

          Plural-Forms: nplurals=2; plural=n != 1;

     (Note: this uses the feature of C expressions that boolean
     expressions have to value zero or one.)

     Languages with this property include:

     Germanic family
          Danish, Dutch, English, German, Norwegian, Swedish
     Finno-Ugric family
          Estonian, Finnish
     Latin/Greek family
          Greek
     Semitic family
          Hebrew
     Romance family
          Italian, Portuguese, Spanish
     Artificial
          Esperanto

Two forms, singular used for zero and one
     Exceptional case in the language family.  The header entry would
     be:

          Plural-Forms: nplurals=2; plural=n>1;

     Languages with this property include:

     Romanic family
          French, Brazilian Portuguese

Three forms, special case for zero
     The header entry would be:

          Plural-Forms: nplurals=3; plural=n%10==1 && n%100!=11 ? 0 : n != 0 ? 1 : 2;

     Languages with this property include:

     Baltic family
          Latvian

Three forms, special cases for one and two
     The header entry would be:

          Plural-Forms: nplurals=3; plural=n==1 ? 0 : n==2 ? 1 : 2;

     Languages with this property include:

     Celtic
          Gaeilge (Irish)

Three forms, special case for numbers ending in 1[2-9]
     The header entry would look like this:

          Plural-Forms: nplurals=3; \
              plural=n%10==1 && n%100!=11 ? 0 : \
                     n%10>=2 && (n%100<10 || n%100>=20) ? 1 : 2;

     Languages with this property include:

     Baltic family
          Lithuanian

Three forms, special cases for numbers ending in 1 and 2, 3, 4, except those ending in 1[1-4]
     The header entry would look like this:

          Plural-Forms: nplurals=3; \
              plural=n%100/10==1 ? 2 : n%10==1 ? 0 : (n+9)%10>3 ? 2 : 1;

     Languages with this property include:

     Slavic family
          Croatian, Czech, Russian, Ukrainian

Three forms, special cases for 1 and 2, 3, 4
     The header entry would look like this:

          Plural-Forms: nplurals=3; \
              plural=(n==1) ? 1 : (n>=2 && n<=4) ? 2 : 0;

     Languages with this property include:

     Slavic family
          Slovak

Three forms, special case for one and some numbers ending in 2, 3, or 4
     The header entry would look like this:

          Plural-Forms: nplurals=3; \
              plural=n==1 ? 0 : \
                     n%10>=2 && n%10<=4 && (n%100<10 || n%100>=20) ? 1 : 2;

     Languages with this property include:

     Slavic family
          Polish

Four forms, special case for one and all numbers ending in 02, 03, or 04
     The header entry would look like this:

          Plural-Forms: nplurals=4; \
              plural=n%100==1 ? 0 : n%100==2 ? 1 : n%100==3 || n%100==4 ? 2 : 3;

     Languages with this property include:

     Slavic family
          Slovenian

   ---------- Footnotes ----------

   (1) Additions are welcome.  Send appropriate information to
<bug-glibc-manual@gnu.org>.


File: libc.info,  Node: Charset conversion in gettext,  Next: GUI program problems,  Prev: Advanced gettext functions,  Up: Message catalogs with gettext

8.2.1.4 How to specify the output character set ‘gettext’ uses
..............................................................

‘gettext’ not only looks up a translation in a message catalog, it also
converts the translation on the fly to the desired output character set.
This is useful if the user is working in a different character set than
the translator who created the message catalog, because it avoids
distributing variants of message catalogs which differ only in the
character set.

   The output character set is, by default, the value of ‘nl_langinfo
(CODESET)’, which depends on the ‘LC_CTYPE’ part of the current locale.
But programs which store strings in a locale independent way (e.g.
UTF-8) can request that ‘gettext’ and related functions return the
translations in that encoding, by use of the ‘bind_textdomain_codeset’
function.

   Note that the MSGID argument to ‘gettext’ is not subject to character
set conversion.  Also, when ‘gettext’ does not find a translation for
MSGID, it returns MSGID unchanged - independently of the current output
character set.  It is therefore recommended that all MSGIDs be US-ASCII
strings.

 -- Function: char * bind_textdomain_codeset (const char *DOMAINNAME,
          const char *CODESET)

     Preliminary: | MT-Safe | AS-Unsafe heap | AC-Unsafe mem | *Note
     POSIX Safety Concepts::.

     The ‘bind_textdomain_codeset’ function can be used to specify the
     output character set for message catalogs for domain DOMAINNAME.
     The CODESET argument must be a valid codeset name which can be used
     for the ‘iconv_open’ function, or a null pointer.

     If the CODESET parameter is the null pointer,
     ‘bind_textdomain_codeset’ returns the currently selected codeset
     for the domain with the name DOMAINNAME.  It returns ‘NULL’ if no
     codeset has yet been selected.

     The ‘bind_textdomain_codeset’ function can be used several times.
     If used multiple times with the same DOMAINNAME argument, the later
     call overrides the settings made by the earlier one.

     The ‘bind_textdomain_codeset’ function returns a pointer to a
     string containing the name of the selected codeset.  The string is
     allocated internally in the function and must not be changed by the
     user.  If the system went out of core during the execution of
     ‘bind_textdomain_codeset’, the return value is ‘NULL’ and the
     global variable ‘errno’ is set accordingly.


File: libc.info,  Node: GUI program problems,  Next: Using gettextized software,  Prev: Charset conversion in gettext,  Up: Message catalogs with gettext

8.2.1.5 How to use ‘gettext’ in GUI programs
............................................

One place where the ‘gettext’ functions, if used normally, have big
problems is within programs with graphical user interfaces (GUIs).  The
problem is that many of the strings which have to be translated are very
short.  They have to appear in pull-down menus which restricts the
length.  But strings which are not containing entire sentences or at
least large fragments of a sentence may appear in more than one
situation in the program but might have different translations.  This is
especially true for the one-word strings which are frequently used in
GUI programs.

   As a consequence many people say that the ‘gettext’ approach is wrong
and instead ‘catgets’ should be used which indeed does not have this
problem.  But there is a very simple and powerful method to handle these
kind of problems with the ‘gettext’ functions.

As an example consider the following fictional situation.  A GUI program
has a menu bar with the following entries:

     +------------+------------+--------------------------------------+
     | File       | Printer    |                                      |
     +------------+------------+--------------------------------------+
     | Open     | | Select   |
     | New      | | Open     |
     +----------+ | Connect  |
                  +----------+

   To have the strings ‘File’, ‘Printer’, ‘Open’, ‘New’, ‘Select’, and
‘Connect’ translated there has to be at some point in the code a call to
a function of the ‘gettext’ family.  But in two places the string passed
into the function would be ‘Open’.  The translations might not be the
same and therefore we are in the dilemma described above.

   One solution to this problem is to artificially extend the strings to
make them unambiguous.  But what would the program do if no translation
is available?  The extended string is not what should be printed.  So we
should use a slightly modified version of the functions.

   To extend the strings a uniform method should be used.  E.g., in the
example above, the strings could be chosen as

     Menu|File
     Menu|Printer
     Menu|File|Open
     Menu|File|New
     Menu|Printer|Select
     Menu|Printer|Open
     Menu|Printer|Connect

   Now all the strings are different and if now instead of ‘gettext’ the
following little wrapper function is used, everything works just fine:

       char *
       sgettext (const char *msgid)
       {
         char *msgval = gettext (msgid);
         if (msgval == msgid)
           msgval = strrchr (msgid, '|') + 1;
         return msgval;
       }

   What this little function does is to recognize the case when no
translation is available.  This can be done very efficiently by a
pointer comparison since the return value is the input value.  If there
is no translation we know that the input string is in the format we used
for the Menu entries and therefore contains a ‘|’ character.  We simply
search for the last occurrence of this character and return a pointer to
the character following it.  That's it!

   If one now consistently uses the extended string form and replaces
the ‘gettext’ calls with calls to ‘sgettext’ (this is normally limited
to very few places in the GUI implementation) then it is possible to
produce a program which can be internationalized.

   With advanced compilers (such as GNU C) one can write the ‘sgettext’
functions as an inline function or as a macro like this:

     #define sgettext(msgid) \
       ({ const char *__msgid = (msgid);            \
          char *__msgstr = gettext (__msgid);       \
          if (__msgval == __msgid)                  \
            __msgval = strrchr (__msgid, '|') + 1;  \
          __msgval; })

   The other ‘gettext’ functions (‘dgettext’, ‘dcgettext’ and the
‘ngettext’ equivalents) can and should have corresponding functions as
well which look almost identical, except for the parameters and the call
to the underlying function.

   Now there is of course the question why such functions do not exist
in the GNU C Library?  There are two parts of the answer to this
question.

   • They are easy to write and therefore can be provided by the project
     they are used in.  This is not an answer by itself and must be seen
     together with the second part which is:

   • There is no way the C library can contain a version which can work
     everywhere.  The problem is the selection of the character to
     separate the prefix from the actual string in the extended string.
     The examples above used ‘|’ which is a quite good choice because it
     resembles a notation frequently used in this context and it also is
     a character not often used in message strings.

     But what if the character is used in message strings.  Or if the
     chose character is not available in the character set on the
     machine one compiles (e.g., ‘|’ is not required to exist for ISO C;
     this is why the ‘iso646.h’ file exists in ISO C programming
     environments).

   There is only one more comment to make left.  The wrapper function
above requires that the translations strings are not extended
themselves.  This is only logical.  There is no need to disambiguate the
strings (since they are never used as keys for a search) and one also
saves quite some memory and disk space by doing this.


File: libc.info,  Node: Using gettextized software,  Prev: GUI program problems,  Up: Message catalogs with gettext

8.2.1.6 User influence on ‘gettext’
...................................

The last sections described what the programmer can do to
internationalize the messages of the program.  But it is finally up to
the user to select the message s/he wants to see.  S/He must understand
them.

   The POSIX locale model uses the environment variables ‘LC_COLLATE’,
‘LC_CTYPE’, ‘LC_MESSAGES’, ‘LC_MONETARY’, ‘LC_NUMERIC’, and ‘LC_TIME’ to
select the locale which is to be used.  This way the user can influence
lots of functions.  As we mentioned above, the ‘gettext’ functions also
take advantage of this.

   To understand how this happens it is necessary to take a look at the
various components of the filename which gets computed to locate a
message catalog.  It is composed as follows:

     DIR_NAME/LOCALE/LC_CATEGORY/DOMAIN_NAME.mo

   The default value for DIR_NAME is system specific.  It is computed
from the value given as the prefix while configuring the C library.
This value normally is ‘/usr’ or ‘/’.  For the former the complete
DIR_NAME is:

     /usr/share/locale

   We can use ‘/usr/share’ since the ‘.mo’ files containing the message
catalogs are system independent, so all systems can use the same files.
If the program executed the ‘bindtextdomain’ function for the message
domain that is currently handled, the ‘dir_name’ component is exactly
the value which was given to the function as the second parameter.
I.e., ‘bindtextdomain’ allows overwriting the only system dependent and
fixed value to make it possible to address files anywhere in the
filesystem.

   The CATEGORY is the name of the locale category which was selected in
the program code.  For ‘gettext’ and ‘dgettext’ this is always
‘LC_MESSAGES’, for ‘dcgettext’ this is selected by the value of the
third parameter.  As said above it should be avoided to ever use a
category other than ‘LC_MESSAGES’.

   The LOCALE component is computed based on the category used.  Just
like for the ‘setlocale’ function here comes the user selection into the
play.  Some environment variables are examined in a fixed order and the
first environment variable set determines the return value of the lookup
process.  In detail, for the category ‘LC_xxx’ the following variables
in this order are examined:

‘LANGUAGE’
‘LC_ALL’
‘LC_xxx’
‘LANG’

   This looks very familiar.  With the exception of the ‘LANGUAGE’
environment variable this is exactly the lookup order the ‘setlocale’
function uses.  But why introduce the ‘LANGUAGE’ variable?

   The reason is that the syntax of the values these variables can have
is different to what is expected by the ‘setlocale’ function.  If we
would set ‘LC_ALL’ to a value following the extended syntax that would
mean the ‘setlocale’ function will never be able to use the value of
this variable as well.  An additional variable removes this problem plus
we can select the language independently of the locale setting which
sometimes is useful.

   While for the ‘LC_xxx’ variables the value should consist of exactly
one specification of a locale the ‘LANGUAGE’ variable's value can
consist of a colon separated list of locale names.  The attentive reader
will realize that this is the way we manage to implement one of our
additional demands above: we want to be able to specify an ordered list
of languages.

   Back to the constructed filename we have only one component missing.
The DOMAIN_NAME part is the name which was either registered using the
‘textdomain’ function or which was given to ‘dgettext’ or ‘dcgettext’ as
the first parameter.  Now it becomes obvious that a good choice for the
domain name in the program code is a string which is closely related to
the program/package name.  E.g., for the GNU C Library the domain name
is ‘libc’.

A limited piece of example code should show how the program is supposed
to work:

     {
       setlocale (LC_ALL, "");
       textdomain ("test-package");
       bindtextdomain ("test-package", "/usr/local/share/locale");
       puts (gettext ("Hello, world!"));
     }

   At the program start the default domain is ‘messages’, and the
default locale is "C". The ‘setlocale’ call sets the locale according to
the user's environment variables; remember that correct functioning of
‘gettext’ relies on the correct setting of the ‘LC_MESSAGES’ locale (for
looking up the message catalog) and of the ‘LC_CTYPE’ locale (for the
character set conversion).  The ‘textdomain’ call changes the default
domain to ‘test-package’.  The ‘bindtextdomain’ call specifies that the
message catalogs for the domain ‘test-package’ can be found below the
directory ‘/usr/local/share/locale’.

   If the user sets in her/his environment the variable ‘LANGUAGE’ to
‘de’ the ‘gettext’ function will try to use the translations from the
file

     /usr/local/share/locale/de/LC_MESSAGES/test-package.mo

   From the above descriptions it should be clear which component of
this filename is determined by which source.

   In the above example we assumed the ‘LANGUAGE’ environment variable
to be ‘de’.  This might be an appropriate selection but what happens if
the user wants to use ‘LC_ALL’ because of the wider usability and here
the required value is ‘de_DE.ISO-8859-1’?  We already mentioned above
that a situation like this is not infrequent.  E.g., a person might
prefer reading a dialect and if this is not available fall back on the
standard language.

   The ‘gettext’ functions know about situations like this and can
handle them gracefully.  The functions recognize the format of the value
of the environment variable.  It can split the value is different pieces
and by leaving out the only or the other part it can construct new
values.  This happens of course in a predictable way.  To understand
this one must know the format of the environment variable value.  There
is one more or less standardized form, originally from the X/Open
specification:

   ‘language[_territory[.codeset]][@modifier]’

   Less specific locale names will be stripped in the order of the
following list:

  1. ‘codeset’
  2. ‘normalized codeset’
  3. ‘territory’
  4. ‘modifier’

   The ‘language’ field will never be dropped for obvious reasons.

   The only new thing is the ‘normalized codeset’ entry.  This is
another goodie which is introduced to help reduce the chaos which
derives from the inability of people to standardize the names of
character sets.  Instead of ISO-8859-1 one can often see 8859-1, 88591,
iso8859-1, or iso_8859-1.  The ‘normalized codeset’ value is generated
from the user-provided character set name by applying the following
rules:

  1. Remove all characters besides numbers and letters.
  2. Fold letters to lowercase.
  3. If the same only contains digits prepend the string ‘"iso"’.

So all of the above names will be normalized to ‘iso88591’.  This allows
the program user much more freedom in choosing the locale name.

   Even this extended functionality still does not help to solve the
problem that completely different names can be used to denote the same
locale (e.g., ‘de’ and ‘german’).  To be of help in this situation the
locale implementation and also the ‘gettext’ functions know about
aliases.

   The file ‘/usr/share/locale/locale.alias’ (replace ‘/usr’ with
whatever prefix you used for configuring the C library) contains a
mapping of alternative names to more regular names.  The system manager
is free to add new entries to fill her/his own needs.  The selected
locale from the environment is compared with the entries in the first
column of this file ignoring the case.  If they match, the value of the
second column is used instead for the further handling.

   In the description of the format of the environment variables we
already mentioned the character set as a factor in the selection of the
message catalog.  In fact, only catalogs which contain text written
using the character set of the system/program can be used (directly;
there will come a solution for this some day).  This means for the user
that s/he will always have to take care of this.  If in the collection
of the message catalogs there are files for the same language but coded
using different character sets the user has to be careful.


File: libc.info,  Node: Helper programs for gettext,  Prev: Message catalogs with gettext,  Up: The Uniforum approach

8.2.2 Programs to handle message catalogs for ‘gettext’
-------------------------------------------------------

The GNU C Library does not contain the source code for the programs to
handle message catalogs for the ‘gettext’ functions.  As part of the GNU
project the GNU gettext package contains everything the developer needs.
The functionality provided by the tools in this package by far exceeds
the abilities of the ‘gencat’ program described above for the ‘catgets’
functions.

   There is a program ‘msgfmt’ which is the equivalent program to the
‘gencat’ program.  It generates from the human-readable and -editable
form of the message catalog a binary file which can be used by the
‘gettext’ functions.  But there are several more programs available.

   The ‘xgettext’ program can be used to automatically extract the
translatable messages from a source file.  I.e., the programmer need not
take care of the translations and the list of messages which have to be
translated.  S/He will simply wrap the translatable string in calls to
‘gettext’ et.al and the rest will be done by ‘xgettext’.  This program
has a lot of options which help to customize the output or help to
understand the input better.

   Other programs help to manage the development cycle when new messages
appear in the source files or when a new translation of the messages
appears.  Here it should only be noted that using all the tools in GNU
gettext it is possible to _completely_ automate the handling of message
catalogs.  Besides marking the translatable strings in the source code
and generating the translations the developers do not have anything to
do themselves.


File: libc.info,  Node: Searching and Sorting,  Next: Pattern Matching,  Prev: Message Translation,  Up: Top

9 Searching and Sorting
***********************

This chapter describes functions for searching and sorting arrays of
arbitrary objects.  You pass the appropriate comparison function to be
applied as an argument, along with the size of the objects in the array
and the total number of elements.

* Menu:

* Comparison Functions::        Defining how to compare two objects.
				 Since the sort and search facilities
                                 are general, you have to specify the
                                 ordering.
* Array Search Function::       The ‘bsearch’ function.
* Array Sort Function::         The ‘qsort’ function.
* Search/Sort Example::         An example program.
* Hash Search Function::        The ‘hsearch’ function.
* Tree Search Function::        The ‘tsearch’ function.


File: libc.info,  Node: Comparison Functions,  Next: Array Search Function,  Up: Searching and Sorting

9.1 Defining the Comparison Function
====================================

In order to use the sorted array library functions, you have to describe
how to compare the elements of the array.

   To do this, you supply a comparison function to compare two elements
of the array.  The library will call this function, passing as arguments
pointers to two array elements to be compared.  Your comparison function
should return a value the way ‘strcmp’ (*note String/Array Comparison::)
does: negative if the first argument is "less" than the second, zero if
they are "equal", and positive if the first argument is "greater".

   Here is an example of a comparison function which works with an array
of numbers of type ‘long int’:

     int
     compare_long_ints (const void *a, const void *b)
     {
       const long int *la = a;
       const long int *lb = b;

       return (*la > *lb) - (*la < *lb);
     }

   (The code would have to be more complicated for an array of ‘double’,
to handle NaNs correctly.)

   The header file ‘stdlib.h’ defines a name for the data type of
comparison functions.  This type is a GNU extension.

     int comparison_fn_t (const void *, const void *);


File: libc.info,  Node: Array Search Function,  Next: Array Sort Function,  Prev: Comparison Functions,  Up: Searching and Sorting

9.2 Array Search Function
=========================

Generally searching for a specific element in an array means that
potentially all elements must be checked.  The GNU C Library contains
functions to perform linear search.  The prototypes for the following
two functions can be found in ‘search.h’.

 -- Function: void * lfind (const void *KEY, const void *BASE, size_t
          *NMEMB, size_t SIZE, comparison_fn_t COMPAR)

     Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
     Concepts::.

     The ‘lfind’ function searches in the array with ‘*NMEMB’ elements
     of SIZE bytes pointed to by BASE for an element which matches the
     one pointed to by KEY.  The function pointed to by COMPAR is used
     to decide whether two elements match.

     The return value is a pointer to the matching element in the array
     starting at BASE if it is found.  If no matching element is
     available ‘NULL’ is returned.

     The mean runtime of this function is proportional to ‘*NMEMB/2’,
     assuming random elements of the array are searched for.  This
     function should be used only if elements often get added to or
     deleted from the array in which case it might not be useful to sort
     the array before searching.

 -- Function: void * lsearch (const void *KEY, void *BASE, size_t
          *NMEMB, size_t SIZE, comparison_fn_t COMPAR)

     Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
     Concepts::.

     The ‘lsearch’ function is similar to the ‘lfind’ function.  It
     searches the given array for an element and returns it if found.
     The difference is that if no matching element is found the
     ‘lsearch’ function adds the object pointed to by KEY (with a size
     of SIZE bytes) at the end of the array and it increments the value
     of ‘*NMEMB’ to reflect this addition.

     This means for the caller that if it is not sure that the array
     contains the element one is searching for the memory allocated for
     the array starting at BASE must have room for at least SIZE more
     bytes.  If one is sure the element is in the array it is better to
     use ‘lfind’ so having more room in the array is always necessary
     when calling ‘lsearch’.

   To search a sorted or partially sorted array for an element matching
the key, use the ‘bsearch’ function.  The prototype for this function is
in the header file ‘stdlib.h’.

 -- Function: void * bsearch (const void *KEY, const void *ARRAY, size_t
          COUNT, size_t SIZE, comparison_fn_t COMPARE)

     Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
     Concepts::.

     The ‘bsearch’ function searches ARRAY for an element that is
     equivalent to KEY.  The array contains COUNT elements, each of
     which is of size SIZE bytes.

     The COMPARE function is used to perform the comparison.  This
     function is called with arguments that point to the key and to an
     array element, in that order, and should return an integer less
     than, equal to, or greater than zero corresponding to whether the
     key is considered less than, equal to, or greater than the array
     element.  The function should not alter the array's contents, and
     the same array element should always compare the same way with the
     key.

     Although the array need not be completely sorted, it should be
     partially sorted with respect to KEY.  That is, the array should
     begin with elements that compare less than KEY, followed by
     elements that compare equal to KEY, and ending with elements that
     compare greater than KEY.  Any or all of these element sequences
     can be empty.

     The return value is a pointer to a matching array element, or a
     null pointer if no match is found.  If the array contains more than
     one element that matches, the one that is returned is unspecified.

     This function derives its name from the fact that it is implemented
     using the binary search algorithm.


File: libc.info,  Node: Array Sort Function,  Next: Search/Sort Example,  Prev: Array Search Function,  Up: Searching and Sorting

9.3 Array Sort Function
=======================

To sort an array using an arbitrary comparison function, use the ‘qsort’
function.  The prototype for this function is in ‘stdlib.h’.

 -- Function: void qsort (void *ARRAY, size_t COUNT, size_t SIZE,
          comparison_fn_t COMPARE)

     Preliminary: | MT-Safe | AS-Safe | AC-Unsafe corrupt | *Note POSIX
     Safety Concepts::.

     The ‘qsort’ function sorts the array ARRAY.  The array contains
     COUNT elements, each of which is of size SIZE.

     The COMPARE function is used to perform the comparison on the array
     elements.  This function is called with two pointer arguments and
     should return an integer less than, equal to, or greater than zero
     corresponding to whether its first argument is considered less
     than, equal to, or greater than its second argument.  The function
     must not alter the array's contents, and must define a total
     ordering on the array elements, including any unusual values such
     as floating-point NaN (*note Infinity and NaN::).  Because the
     sorting process can move elements, the function's return value must
     not depend on the element addresses or the relative positions of
     elements within the array, as these are meaningless while ‘qsort’
     is running.

     *Warning:* If two elements compare equal, their order after sorting
     is unpredictable.  That is to say, the sorting is not stable.  This
     can make a difference when the comparison considers only part of
     the elements and two elements that compare equal may differ in
     other respects.  To ensure a stable sort in this situation, you can
     augment each element with an appropriate tie-breaking value, such
     as its original array index.

     Here is a simple example of sorting an array of ‘long int’ in
     numerical order, using the comparison function defined above (*note
     Comparison Functions::):

          {
            long int *array;
            size_t nmemb;
            ...
            qsort (array, nmemb, sizeof *array, compare_long_ints);
          }

     The ‘qsort’ function derives its name from the fact that it was
     originally implemented using the "quick sort" algorithm.

     The implementation of ‘qsort’ attempts to allocate auxiliary memory
     and use the merge sort algorithm, without violating C standard
     requirement that arguments passed to the comparison function point
     within the array.  If the memory allocation fails, ‘qsort’ resorts
     to a slower algorithm.


File: libc.info,  Node: Search/Sort Example,  Next: Hash Search Function,  Prev: Array Sort Function,  Up: Searching and Sorting

9.4 Searching and Sorting Example
=================================

Here is an example showing the use of ‘qsort’ and ‘bsearch’ with an
array of structures.  The elements of the array are sorted by comparing
their ‘name’ fields with the ‘strcmp’ function.  Then, we can look up
individual elements based on their names.


     #include <stdlib.h>
     #include <stdio.h>
     #include <string.h>

     /* Define an array of critters to sort. */

     struct critter
       {
         const char *name;
         const char *species;
       };

     struct critter muppets[] =
       {
         {"Kermit", "frog"},
         {"Piggy", "pig"},
         {"Gonzo", "whatever"},
         {"Fozzie", "bear"},
         {"Sam", "eagle"},
         {"Robin", "frog"},
         {"Animal", "animal"},
         {"Camilla", "chicken"},
         {"Sweetums", "monster"},
         {"Dr. Strangepork", "pig"},
         {"Link Hogthrob", "pig"},
         {"Zoot", "human"},
         {"Dr. Bunsen Honeydew", "human"},
         {"Beaker", "human"},
         {"Swedish Chef", "human"}
       };

     int count = sizeof (muppets) / sizeof (struct critter);



     /* This is the comparison function used for sorting and searching. */

     int
     critter_cmp (const void *v1, const void *v2)
     {
       const struct critter *c1 = v1;
       const struct critter *c2 = v2;

       return strcmp (c1->name, c2->name);
     }


     /* Print information about a critter. */

     void
     print_critter (const struct critter *c)
     {
       printf ("%s, the %s\n", c->name, c->species);
     }


     /* Do the lookup into the sorted array. */

     void
     find_critter (const char *name)
     {
       struct critter target, *result;
       target.name = name;
       result = bsearch (&target, muppets, count, sizeof (struct critter),
                         critter_cmp);
       if (result)
         print_critter (result);
       else
         printf ("Couldn't find %s.\n", name);
     }

     /* Main program. */

     int
     main (void)
     {
       int i;

       for (i = 0; i < count; i++)
         print_critter (&muppets[i]);
       printf ("\n");

       qsort (muppets, count, sizeof (struct critter), critter_cmp);

       for (i = 0; i < count; i++)
         print_critter (&muppets[i]);
       printf ("\n");

       find_critter ("Kermit");
       find_critter ("Gonzo");
       find_critter ("Janice");

       return 0;
     }

   The output from this program looks like:

     Kermit, the frog
     Piggy, the pig
     Gonzo, the whatever
     Fozzie, the bear
     Sam, the eagle
     Robin, the frog
     Animal, the animal
     Camilla, the chicken
     Sweetums, the monster
     Dr. Strangepork, the pig
     Link Hogthrob, the pig
     Zoot, the human
     Dr. Bunsen Honeydew, the human
     Beaker, the human
     Swedish Chef, the human

     Animal, the animal
     Beaker, the human
     Camilla, the chicken
     Dr. Bunsen Honeydew, the human
     Dr. Strangepork, the pig
     Fozzie, the bear
     Gonzo, the whatever
     Kermit, the frog
     Link Hogthrob, the pig
     Piggy, the pig
     Robin, the frog
     Sam, the eagle
     Swedish Chef, the human
     Sweetums, the monster
     Zoot, the human

     Kermit, the frog
     Gonzo, the whatever
     Couldn't find Janice.


File: libc.info,  Node: Hash Search Function,  Next: Tree Search Function,  Prev: Search/Sort Example,  Up: Searching and Sorting

9.5 The ‘hsearch’ function.
===========================

The functions mentioned so far in this chapter are for searching in a
sorted or unsorted array.  There are other methods to organize
information which later should be searched.  The costs of insert, delete
and search differ.  One possible implementation is using hashing tables.
The following functions are declared in the header file ‘search.h’.

 -- Function: int hcreate (size_t NEL)

     Preliminary: | MT-Unsafe race:hsearch | AS-Unsafe heap | AC-Unsafe
     corrupt mem | *Note POSIX Safety Concepts::.

     The ‘hcreate’ function creates a hashing table which can contain at
     least NEL elements.  There is no possibility to grow this table so
     it is necessary to choose the value for NEL wisely.  The method
     used to implement this function might make it necessary to make the
     number of elements in the hashing table larger than the expected
     maximal number of elements.  Hashing tables usually work
     inefficiently if they are filled 80% or more.  The constant access
     time guaranteed by hashing can only be achieved if few collisions
     exist.  See Knuth's "The Art of Computer Programming, Part 3:
     Searching and Sorting" for more information.

     The weakest aspect of this function is that there can be at most
     one hashing table used through the whole program.  The table is
     allocated in local memory out of control of the programmer.  As an
     extension the GNU C Library provides an additional set of functions
     with a reentrant interface which provides a similar interface but
     which allows keeping arbitrarily many hashing tables.

     It is possible to use more than one hashing table in the program
     run if the former table is first destroyed by a call to ‘hdestroy’.

     The function returns a non-zero value if successful.  If it returns
     zero, something went wrong.  This could either mean there is
     already a hashing table in use or the program ran out of memory.

 -- Function: void hdestroy (void)

     Preliminary: | MT-Unsafe race:hsearch | AS-Unsafe heap | AC-Unsafe
     corrupt mem | *Note POSIX Safety Concepts::.

     The ‘hdestroy’ function can be used to free all the resources
     allocated in a previous call of ‘hcreate’.  After a call to this
     function it is again possible to call ‘hcreate’ and allocate a new
     table with possibly different size.

     It is important to remember that the elements contained in the
     hashing table at the time ‘hdestroy’ is called are _not_ freed by
     this function.  It is the responsibility of the program code to
     free those strings (if necessary at all).  Freeing all the element
     memory is not possible without extra, separately kept information
     since there is no function to iterate through all available
     elements in the hashing table.  If it is really necessary to free a
     table and all elements the programmer has to keep a list of all
     table elements and before calling ‘hdestroy’ s/he has to free all
     element's data using this list.  This is a very unpleasant
     mechanism and it also shows that this kind of hashing table is
     mainly meant for tables which are created once and used until the
     end of the program run.

   Entries of the hashing table and keys for the search are defined
using this type:

 -- Data type: ENTRY
     ‘char *key’
          Pointer to a zero-terminated string of characters describing
          the key for the search or the element in the hashing table.

          This is a limiting restriction of the functionality of the
          ‘hsearch’ functions: They can only be used for data sets which
          use the NUL character always and solely to terminate keys.  It
          is not possible to handle general binary data for keys.

     ‘void *data’
          Generic pointer for use by the application.  The hashing table
          implementation preserves this pointer in entries, but does not
          use it in any way otherwise.

 -- Data type: struct entry
     The underlying type of ‘ENTRY’.

 -- Function: ENTRY * hsearch (ENTRY ITEM, ACTION ACTION)

     Preliminary: | MT-Unsafe race:hsearch | AS-Unsafe | AC-Unsafe
     corrupt/action==ENTER | *Note POSIX Safety Concepts::.

     To search in a hashing table created using ‘hcreate’ the ‘hsearch’
     function must be used.  This function can perform a simple search
     for an element (if ACTION has the value ‘FIND’) or it can
     alternatively insert the key element into the hashing table.
     Entries are never replaced.

     The key is denoted by a pointer to an object of type ‘ENTRY’.  For
     locating the corresponding position in the hashing table only the
     ‘key’ element of the structure is used.

     If an entry with a matching key is found the ACTION parameter is
     irrelevant.  The found entry is returned.  If no matching entry is
     found and the ACTION parameter has the value ‘FIND’ the function
     returns a ‘NULL’ pointer.  If no entry is found and the ACTION
     parameter has the value ‘ENTER’ a new entry is added to the hashing
     table which is initialized with the parameter ITEM.  A pointer to
     the newly added entry is returned.

   As mentioned before, the hashing table used by the functions
described so far is global and there can be at any time at most one
hashing table in the program.  A solution is to use the following
functions which are a GNU extension.  All have in common that they
operate on a hashing table which is described by the content of an
object of the type ‘struct hsearch_data’.  This type should be treated
as opaque, none of its members should be changed directly.

 -- Function: int hcreate_r (size_t NEL, struct hsearch_data *HTAB)

     Preliminary: | MT-Safe race:htab | AS-Unsafe heap | AC-Unsafe
     corrupt mem | *Note POSIX Safety Concepts::.

     The ‘hcreate_r’ function initializes the object pointed to by HTAB
     to contain a hashing table with at least NEL elements.  So this
     function is equivalent to the ‘hcreate’ function except that the
     initialized data structure is controlled by the user.

     This allows having more than one hashing table at one time.  The
     memory necessary for the ‘struct hsearch_data’ object can be
     allocated dynamically.  It must be initialized with zero before
     calling this function.

     The return value is non-zero if the operation was successful.  If
     the return value is zero, something went wrong, which probably
     means the program ran out of memory.

 -- Function: void hdestroy_r (struct hsearch_data *HTAB)

     Preliminary: | MT-Safe race:htab | AS-Unsafe heap | AC-Unsafe
     corrupt mem | *Note POSIX Safety Concepts::.

     The ‘hdestroy_r’ function frees all resources allocated by the
     ‘hcreate_r’ function for this very same object HTAB.  As for
     ‘hdestroy’ it is the program's responsibility to free the strings
     for the elements of the table.

 -- Function: int hsearch_r (ENTRY ITEM, ACTION ACTION, ENTRY **RETVAL,
          struct hsearch_data *HTAB)

     Preliminary: | MT-Safe race:htab | AS-Safe | AC-Unsafe
     corrupt/action==ENTER | *Note POSIX Safety Concepts::.

     The ‘hsearch_r’ function is equivalent to ‘hsearch’.  The meaning
     of the first two arguments is identical.  But instead of operating
     on a single global hashing table the function works on the table
     described by the object pointed to by HTAB (which is initialized by
     a call to ‘hcreate_r’).

     Another difference to ‘hcreate’ is that the pointer to the found
     entry in the table is not the return value of the function.  It is
     returned by storing it in a pointer variable pointed to by the
     RETVAL parameter.  The return value of the function is an integer
     value indicating success if it is non-zero and failure if it is
     zero.  In the latter case the global variable ‘errno’ signals the
     reason for the failure.

     ‘ENOMEM’
          The table is filled and ‘hsearch_r’ was called with a so far
          unknown key and ACTION set to ‘ENTER’.
     ‘ESRCH’
          The ACTION parameter is ‘FIND’ and no corresponding element is
          found in the table.


File: libc.info,  Node: Tree Search Function,  Prev: Hash Search Function,  Up: Searching and Sorting

9.6 The ‘tsearch’ function.
===========================

Another common form to organize data for efficient search is to use
trees.  The ‘tsearch’ function family provides a nice interface to
functions to organize possibly large amounts of data by providing a mean
access time proportional to the logarithm of the number of elements.
The GNU C Library implementation even guarantees that this bound is
never exceeded even for input data which cause problems for simple
binary tree implementations.

   The functions described in the chapter are all described in the
System V and X/Open specifications and are therefore quite portable.

   In contrast to the ‘hsearch’ functions the ‘tsearch’ functions can be
used with arbitrary data and not only zero-terminated strings.

   The ‘tsearch’ functions have the advantage that no function to
initialize data structures is necessary.  A simple pointer of type ‘void
*’ initialized to ‘NULL’ is a valid tree and can be extended or
searched.  The prototypes for these functions can be found in the header
file ‘search.h’.

 -- Function: void * tsearch (const void *KEY, void **ROOTP,
          comparison_fn_t COMPAR)

     Preliminary: | MT-Safe race:rootp | AS-Unsafe heap | AC-Unsafe
     corrupt mem | *Note POSIX Safety Concepts::.

     The ‘tsearch’ function searches in the tree pointed to by ‘*ROOTP’
     for an element matching KEY.  The function pointed to by COMPAR is
     used to determine whether two elements match.  *Note Comparison
     Functions::, for a specification of the functions which can be used
     for the COMPAR parameter.

     If the tree does not contain a matching entry the KEY value will be
     added to the tree.  ‘tsearch’ does not make a copy of the object
     pointed to by KEY (how could it since the size is unknown).
     Instead it adds a reference to this object which means the object
     must be available as long as the tree data structure is used.

     The tree is represented by a pointer to a pointer since it is
     sometimes necessary to change the root node of the tree.  So it
     must not be assumed that the variable pointed to by ROOTP has the
     same value after the call.  This also shows that it is not safe to
     call the ‘tsearch’ function more than once at the same time using
     the same tree.  It is no problem to run it more than once at a time
     on different trees.

     The return value is a pointer to the matching element in the tree.
     If a new element was created the pointer points to the new data
     (which is in fact KEY).  If an entry had to be created and the
     program ran out of space ‘NULL’ is returned.

 -- Function: void * tfind (const void *KEY, void *const *ROOTP,
          comparison_fn_t COMPAR)

     Preliminary: | MT-Safe race:rootp | AS-Safe | AC-Safe | *Note POSIX
     Safety Concepts::.

     The ‘tfind’ function is similar to the ‘tsearch’ function.  It
     locates an element matching the one pointed to by KEY and returns a
     pointer to this element.  But if no matching element is available
     no new element is entered (note that the ROOTP parameter points to
     a constant pointer).  Instead the function returns ‘NULL’.

   Another advantage of the ‘tsearch’ functions in contrast to the
‘hsearch’ functions is that there is an easy way to remove elements.

 -- Function: void * tdelete (const void *KEY, void **ROOTP,
          comparison_fn_t COMPAR)

     Preliminary: | MT-Safe race:rootp | AS-Unsafe heap | AC-Unsafe
     corrupt mem | *Note POSIX Safety Concepts::.

     To remove a specific element matching KEY from the tree ‘tdelete’
     can be used.  It locates the matching element using the same method
     as ‘tfind’.  The corresponding element is then removed and a
     pointer to the parent of the deleted node is returned by the
     function.  If there is no matching entry in the tree nothing can be
     deleted and the function returns ‘NULL’.  If the root of the tree
     is deleted ‘tdelete’ returns some unspecified value not equal to
     ‘NULL’.

 -- Function: void tdestroy (void *VROOT, __free_fn_t FREEFCT)

     Preliminary: | MT-Safe | AS-Unsafe heap | AC-Unsafe mem | *Note
     POSIX Safety Concepts::.

     If the complete search tree has to be removed one can use
     ‘tdestroy’.  It frees all resources allocated by the ‘tsearch’
     functions to generate the tree pointed to by VROOT.

     For the data in each tree node the function FREEFCT is called.  The
     pointer to the data is passed as the argument to the function.  If
     no such work is necessary FREEFCT must point to a function doing
     nothing.  It is called in any case.

     This function is a GNU extension and not covered by the System V or
     X/Open specifications.

   In addition to the functions to create and destroy the tree data
structure, there is another function which allows you to apply a
function to all elements of the tree.  The function must have this type:

     void __action_fn_t (const void *nodep, VISIT value, int level);

   The NODEP is the data value of the current node (once given as the
KEY argument to ‘tsearch’).  LEVEL is a numeric value which corresponds
to the depth of the current node in the tree.  The root node has the
depth 0 and its children have a depth of 1 and so on.  The ‘VISIT’ type
is an enumeration type.

 -- Data Type: VISIT
     The ‘VISIT’ value indicates the status of the current node in the
     tree and how the function is called.  The status of a node is
     either 'leaf' or 'internal node'.  For each leaf node the function
     is called exactly once, for each internal node it is called three
     times: before the first child is processed, after the first child
     is processed and after both children are processed.  This makes it
     possible to handle all three methods of tree traversal (or even a
     combination of them).

     ‘preorder’
          The current node is an internal node and the function is
          called before the first child was processed.
     ‘postorder’
          The current node is an internal node and the function is
          called after the first child was processed.
     ‘endorder’
          The current node is an internal node and the function is
          called after the second child was processed.
     ‘leaf’
          The current node is a leaf.

 -- Function: void twalk (const void *ROOT, __action_fn_t ACTION)

     Preliminary: | MT-Safe race:root | AS-Safe | AC-Safe | *Note POSIX
     Safety Concepts::.

     For each node in the tree with a node pointed to by ROOT, the
     ‘twalk’ function calls the function provided by the parameter
     ACTION.  For leaf nodes the function is called exactly once with
     VALUE set to ‘leaf’.  For internal nodes the function is called
     three times, setting the VALUE parameter or ACTION to the
     appropriate value.  The LEVEL argument for the ACTION function is
     computed while descending the tree by increasing the value by one
     for each descent to a child, starting with the value 0 for the root
     node.

     Since the functions used for the ACTION parameter to ‘twalk’ must
     not modify the tree data, it is safe to run ‘twalk’ in more than
     one thread at the same time, working on the same tree.  It is also
     safe to call ‘tfind’ in parallel.  Functions which modify the tree
     must not be used, otherwise the behavior is undefined.  However, it
     is difficult to pass data external to the tree to the callback
     function without resorting to global variables (and thread safety
     issues), so see the ‘twalk_r’ function below.

 -- Function: void twalk_r (const void *ROOT, void (*ACTION) (const void
          *KEY, VISIT WHICH, void *CLOSURE), void *CLOSURE)

     Preliminary: | MT-Safe race:root | AS-Safe | AC-Safe | *Note POSIX
     Safety Concepts::.

     For each node in the tree with a node pointed to by ROOT, the
     ‘twalk_r’ function calls the function provided by the parameter
     ACTION.  For leaf nodes the function is called exactly once with
     WHICH set to ‘leaf’.  For internal nodes the function is called
     three times, setting the WHICH parameter of ACTION to the
     appropriate value.  The CLOSURE parameter is passed down to each
     call of the ACTION function, unmodified.

     It is possible to implement the ‘twalk’ function on top of the
     ‘twalk_r’ function, which is why there is no separate level
     parameter.


          #include <search.h>

          struct twalk_with_twalk_r_closure
          {
            void (*action) (const void *, VISIT, int);
            int depth;
          };

          static void
          twalk_with_twalk_r_action (const void *nodep, VISIT which, void *closure0)
          {
            struct twalk_with_twalk_r_closure *closure = closure0;

            switch (which)
              {
              case leaf:
                closure->action (nodep, which, closure->depth);
                break;
              case preorder:
                closure->action (nodep, which, closure->depth);
                ++closure->depth;
                break;
              case postorder:
                /* The preorder action incremented the depth. */
                closure->action (nodep, which, closure->depth - 1);
                break;
              case endorder:
                --closure->depth;
                closure->action (nodep, which, closure->depth);
                break;
              }
          }

          void
          twalk (const void *root, void (*action) (const void *, VISIT, int))
          {
            struct twalk_with_twalk_r_closure closure = { action, 0 };
            twalk_r (root, twalk_with_twalk_r_action, &closure);
          }


File: libc.info,  Node: Pattern Matching,  Next: I/O Overview,  Prev: Searching and Sorting,  Up: Top

10 Pattern Matching
*******************

The GNU C Library provides pattern matching facilities for two kinds of
patterns: regular expressions and file-name wildcards.  The library also
provides a facility for expanding variable and command references and
parsing text into words in the way the shell does.

* Menu:

* Wildcard Matching::    Matching a wildcard pattern against a single string.
* Globbing::             Finding the files that match a wildcard pattern.
* Regular Expressions::  Matching regular expressions against strings.
* Word Expansion::       Expanding shell variables, nested commands,
			    arithmetic, and wildcards.
			    This is what the shell does with shell commands.


File: libc.info,  Node: Wildcard Matching,  Next: Globbing,  Up: Pattern Matching

10.1 Wildcard Matching
======================

This section describes how to match a wildcard pattern against a
particular string.  The result is a yes or no answer: does the string
fit the pattern or not.  The symbols described here are all declared in
‘fnmatch.h’.

 -- Function: int fnmatch (const char *PATTERN, const char *STRING, int
          FLAGS)

     Preliminary: | MT-Safe env locale | AS-Unsafe heap | AC-Unsafe mem
     | *Note POSIX Safety Concepts::.

     This function tests whether the string STRING matches the pattern
     PATTERN.  It returns ‘0’ if they do match; otherwise, it returns
     the nonzero value ‘FNM_NOMATCH’.  The arguments PATTERN and STRING
     are both strings.

     The argument FLAGS is a combination of flag bits that alter the
     details of matching.  See below for a list of the defined flags.

     In the GNU C Library, ‘fnmatch’ might sometimes report "errors" by
     returning nonzero values that are not equal to ‘FNM_NOMATCH’.

   These are the available flags for the FLAGS argument:

‘FNM_FILE_NAME’

     Treat the ‘/’ character specially, for matching file names.  If
     this flag is set, wildcard constructs in PATTERN cannot match ‘/’
     in STRING.  Thus, the only way to match ‘/’ is with an explicit ‘/’
     in PATTERN.

‘FNM_PATHNAME’

     This is an alias for ‘FNM_FILE_NAME’; it comes from POSIX.2.  We
     don't recommend this name because we don't use the term "pathname"
     for file names.

‘FNM_PERIOD’

     Treat the ‘.’ character specially if it appears at the beginning of
     STRING.  If this flag is set, wildcard constructs in PATTERN cannot
     match ‘.’ as the first character of STRING.

     If you set both ‘FNM_PERIOD’ and ‘FNM_FILE_NAME’, then the special
     treatment applies to ‘.’ following ‘/’ as well as to ‘.’ at the
     beginning of STRING.  (The shell uses the ‘FNM_PERIOD’ and
     ‘FNM_FILE_NAME’ flags together for matching file names.)

‘FNM_NOESCAPE’

     Don't treat the ‘\’ character specially in patterns.  Normally, ‘\’
     quotes the following character, turning off its special meaning (if
     any) so that it matches only itself.  When quoting is enabled, the
     pattern ‘\?’ matches only the string ‘?’, because the question mark
     in the pattern acts like an ordinary character.

     If you use ‘FNM_NOESCAPE’, then ‘\’ is an ordinary character.

‘FNM_LEADING_DIR’

     Ignore a trailing sequence of characters starting with a ‘/’ in
     STRING; that is to say, test whether STRING starts with a directory
     name that PATTERN matches.

     If this flag is set, either ‘foo*’ or ‘foobar’ as a pattern would
     match the string ‘foobar/frobozz’.

‘FNM_CASEFOLD’

     Ignore case in comparing STRING to PATTERN.

     This macro was originally a GNU extension, but was added in
     POSIX.1-2024.

‘FNM_EXTMATCH’

     Besides the normal patterns, also recognize the extended patterns
     introduced in ‘ksh’.  The patterns are written in the form
     explained in the following table where PATTERN-LIST is a ‘|’
     separated list of patterns.

     ‘?(PATTERN-LIST)’
          The pattern matches if zero or one occurrences of any of the
          patterns in the PATTERN-LIST allow matching the input string.

     ‘*(PATTERN-LIST)’
          The pattern matches if zero or more occurrences of any of the
          patterns in the PATTERN-LIST allow matching the input string.

     ‘+(PATTERN-LIST)’
          The pattern matches if one or more occurrences of any of the
          patterns in the PATTERN-LIST allow matching the input string.

     ‘@(PATTERN-LIST)’
          The pattern matches if exactly one occurrence of any of the
          patterns in the PATTERN-LIST allows matching the input string.

     ‘!(PATTERN-LIST)’
          The pattern matches if the input string cannot be matched with
          any of the patterns in the PATTERN-LIST.


File: libc.info,  Node: Globbing,  Next: Regular Expressions,  Prev: Wildcard Matching,  Up: Pattern Matching

10.2 Globbing
=============

The archetypal use of wildcards is for matching against the files in a
directory, and making a list of all the matches.  This is called
“globbing”.

   You could do this using ‘fnmatch’, by reading the directory entries
one by one and testing each one with ‘fnmatch’.  But that would be slow
(and complex, since you would have to handle subdirectories by hand).

   The library provides a function ‘glob’ to make this particular use of
wildcards convenient.  ‘glob’ and the other symbols in this section are
declared in ‘glob.h’.

* Menu:

* Calling Glob::             Basic use of ‘glob’.
* Flags for Globbing::       Flags that enable various options in ‘glob’.
* More Flags for Globbing::  GNU specific extensions to ‘glob’.


File: libc.info,  Node: Calling Glob,  Next: Flags for Globbing,  Up: Globbing

10.2.1 Calling ‘glob’
---------------------

The result of globbing is a vector of file names (strings).  To return
this vector, ‘glob’ uses a special data type, ‘glob_t’, which is a
structure.  You pass ‘glob’ the address of the structure, and it fills
in the structure's fields to tell you about the results.

 -- Data Type: glob_t

     This data type holds a pointer to a word vector.  More precisely,
     it records both the address of the word vector and its size.  The
     GNU implementation contains some more fields which are non-standard
     extensions.

     ‘gl_pathc’
          The number of elements in the vector, excluding the initial
          null entries if the GLOB_DOOFFS flag is used (see gl_offs
          below).

     ‘gl_pathv’
          The address of the vector.  This field has type ‘char **’.

     ‘gl_offs’
          The offset of the first real element of the vector, from its
          nominal address in the ‘gl_pathv’ field.  Unlike the other
          fields, this is always an input to ‘glob’, rather than an
          output from it.

          If you use a nonzero offset, then that many elements at the
          beginning of the vector are left empty.  (The ‘glob’ function
          fills them with null pointers.)

          The ‘gl_offs’ field is meaningful only if you use the
          ‘GLOB_DOOFFS’ flag.  Otherwise, the offset is always zero
          regardless of what is in this field, and the first real
          element comes at the beginning of the vector.

     ‘gl_closedir’
          The address of an alternative implementation of the ‘closedir’
          function.  It is used if the ‘GLOB_ALTDIRFUNC’ bit is set in
          the flag parameter.  The type of this field is
          ‘void (*) (void *)’.

          This is a GNU extension.

     ‘gl_readdir’
          The address of an alternative implementation of the ‘readdir’
          function used to read the contents of a directory.  It is used
          if the ‘GLOB_ALTDIRFUNC’ bit is set in the flag parameter.
          The type of this field is ‘struct dirent *(*) (void *)’.

          An implementation of ‘gl_readdir’ needs to initialize the
          following members of the ‘struct dirent’ object:

          ‘d_type’
               This member should be set to the file type of the entry
               if it is known.  Otherwise, the value ‘DT_UNKNOWN’ can be
               used.  The ‘glob’ function may use the specified file
               type to avoid callbacks in cases where the file type
               indicates that the data is not required.

          ‘d_ino’
               This member needs to be non-zero, otherwise ‘glob’ may
               skip the current entry and call the ‘gl_readdir’ callback
               function again to retrieve another entry.

          ‘d_name’
               This member must be set to the name of the entry.  It
               must be null-terminated.

          The example below shows how to allocate a ‘struct dirent’
          object containing a given name.


               #include <dirent.h>
               #include <errno.h>
               #include <stddef.h>
               #include <stdlib.h>
               #include <string.h>

               struct dirent *
               mkdirent (const char *name)
               {
                 size_t dirent_size = offsetof (struct dirent, d_name) + 1;
                 size_t name_length = strlen (name);
                 size_t total_size = dirent_size + name_length;
                 if (total_size < dirent_size)
                   {
                     errno = ENOMEM;
                     return NULL;
                   }
                 struct dirent *result = malloc (total_size);
                 if (result == NULL)
                   return NULL;
                 result->d_type = DT_UNKNOWN;
                 result->d_ino = 1;            /* Do not skip this entry. */
                 memcpy (result->d_name, name, name_length + 1);
                 return result;
               }

          The ‘glob’ function reads the ‘struct dirent’ members listed
          above and makes a copy of the file name in the ‘d_name’ member
          immediately after the ‘gl_readdir’ callback function returns.
          Future invocations of any of the callback functions may
          deallocate or reuse the buffer.  It is the responsibility of
          the caller of the ‘glob’ function to allocate and deallocate
          the buffer, around the call to ‘glob’ or using the callback
          functions.  For example, an application could allocate the
          buffer in the ‘gl_readdir’ callback function, and deallocate
          it in the ‘gl_closedir’ callback function.

          The ‘gl_readdir’ member is a GNU extension.

     ‘gl_opendir’
          The address of an alternative implementation of the ‘opendir’
          function.  It is used if the ‘GLOB_ALTDIRFUNC’ bit is set in
          the flag parameter.  The type of this field is
          ‘void *(*) (const char *)’.

          This is a GNU extension.

     ‘gl_stat’
          The address of an alternative implementation of the ‘stat’
          function to get information about an object in the filesystem.
          It is used if the ‘GLOB_ALTDIRFUNC’ bit is set in the flag
          parameter.  The type of this field is
          ‘int (*) (const char *, struct stat *)’.

          This is a GNU extension.

     ‘gl_lstat’
          The address of an alternative implementation of the ‘lstat’
          function to get information about an object in the
          filesystems, not following symbolic links.  It is used if the
          ‘GLOB_ALTDIRFUNC’ bit is set in the flag parameter.  The type
          of this field is ‘int (*) (const char *, struct stat *)’.

          This is a GNU extension.

     ‘gl_flags’
          The flags used when ‘glob’ was called.  In addition,
          ‘GLOB_MAGCHAR’ might be set.  See *note Flags for Globbing::
          for more details.

          This is a GNU extension.

   For use in the ‘glob64’ function ‘glob.h’ contains another definition
for a very similar type.  ‘glob64_t’ differs from ‘glob_t’ only in the
types of the members ‘gl_readdir’, ‘gl_stat’, and ‘gl_lstat’.

 -- Data Type: glob64_t

     This data type holds a pointer to a word vector.  More precisely,
     it records both the address of the word vector and its size.  The
     GNU implementation contains some more fields which are non-standard
     extensions.

     ‘gl_pathc’
          The number of elements in the vector, excluding the initial
          null entries if the GLOB_DOOFFS flag is used (see gl_offs
          below).

     ‘gl_pathv’
          The address of the vector.  This field has type ‘char **’.

     ‘gl_offs’
          The offset of the first real element of the vector, from its
          nominal address in the ‘gl_pathv’ field.  Unlike the other
          fields, this is always an input to ‘glob’, rather than an
          output from it.

          If you use a nonzero offset, then that many elements at the
          beginning of the vector are left empty.  (The ‘glob’ function
          fills them with null pointers.)

          The ‘gl_offs’ field is meaningful only if you use the
          ‘GLOB_DOOFFS’ flag.  Otherwise, the offset is always zero
          regardless of what is in this field, and the first real
          element comes at the beginning of the vector.

     ‘gl_closedir’
          The address of an alternative implementation of the ‘closedir’
          function.  It is used if the ‘GLOB_ALTDIRFUNC’ bit is set in
          the flag parameter.  The type of this field is
          ‘void (*) (void *)’.

          This is a GNU extension.

     ‘gl_readdir’
          The address of an alternative implementation of the
          ‘readdir64’ function used to read the contents of a directory.
          It is used if the ‘GLOB_ALTDIRFUNC’ bit is set in the flag
          parameter.  The type of this field is
          ‘struct dirent64 *(*) (void *)’.

          This is a GNU extension.

     ‘gl_opendir’
          The address of an alternative implementation of the ‘opendir’
          function.  It is used if the ‘GLOB_ALTDIRFUNC’ bit is set in
          the flag parameter.  The type of this field is
          ‘void *(*) (const char *)’.

          This is a GNU extension.

     ‘gl_stat’
          The address of an alternative implementation of the ‘stat64’
          function to get information about an object in the filesystem.
          It is used if the ‘GLOB_ALTDIRFUNC’ bit is set in the flag
          parameter.  The type of this field is
          ‘int (*) (const char *, struct stat64 *)’.

          This is a GNU extension.

     ‘gl_lstat’
          The address of an alternative implementation of the ‘lstat64’
          function to get information about an object in the
          filesystems, not following symbolic links.  It is used if the
          ‘GLOB_ALTDIRFUNC’ bit is set in the flag parameter.  The type
          of this field is ‘int (*) (const char *, struct stat64 *)’.

          This is a GNU extension.

     ‘gl_flags’
          The flags used when ‘glob’ was called.  In addition,
          ‘GLOB_MAGCHAR’ might be set.  See *note Flags for Globbing::
          for more details.

          This is a GNU extension.

 -- Function: int glob (const char *PATTERN, int FLAGS, int (*ERRFUNC)
          (const char *FILENAME, int ERROR-CODE), glob_t *VECTOR-PTR)

     Preliminary: | MT-Unsafe race:utent env sig:ALRM timer locale |
     AS-Unsafe dlopen plugin corrupt heap lock | AC-Unsafe corrupt lock
     fd mem | *Note POSIX Safety Concepts::.

     The function ‘glob’ does globbing using the pattern PATTERN in the
     current directory.  It puts the result in a newly allocated vector,
     and stores the size and address of this vector into ‘*VECTOR-PTR’.
     The argument FLAGS is a combination of bit flags; see *note Flags
     for Globbing::, for details of the flags.

     The result of globbing is a sequence of file names.  The function
     ‘glob’ allocates a string for each resulting word, then allocates a
     vector of type ‘char **’ to store the addresses of these strings.
     The last element of the vector is a null pointer.  This vector is
     called the “word vector”.

     To return this vector, ‘glob’ stores both its address and its
     length (number of elements, not counting the terminating null
     pointer) into ‘*VECTOR-PTR’.

     Normally, ‘glob’ sorts the file names alphabetically before
     returning them.  You can turn this off with the flag ‘GLOB_NOSORT’
     if you want to get the information as fast as possible.  Usually
     it's a good idea to let ‘glob’ sort them--if you process the files
     in alphabetical order, the users will have a feel for the rate of
     progress that your application is making.

     If ‘glob’ succeeds, it returns 0.  Otherwise, it returns one of
     these error codes:

     ‘GLOB_ABORTED’

          There was an error opening a directory, and you used the flag
          ‘GLOB_ERR’ or your specified ERRFUNC returned a nonzero value.
          *Note Flags for Globbing::, for an explanation of the
          ‘GLOB_ERR’ flag and ERRFUNC.

     ‘GLOB_NOMATCH’

          The pattern didn't match any existing files.  If you use the
          ‘GLOB_NOCHECK’ flag, then you never get this error code,
          because that flag tells ‘glob’ to _pretend_ that the pattern
          matched at least one file.

     ‘GLOB_NOSPACE’

          It was impossible to allocate memory to hold the result.

     In the event of an error, ‘glob’ stores information in
     ‘*VECTOR-PTR’ about all the matches it has found so far.

     It is important to notice that the ‘glob’ function will not fail if
     it encounters directories or files which cannot be handled without
     the LFS interfaces.  The implementation of ‘glob’ is supposed to
     use these functions internally.  This at least is the assumption
     made by the Unix standard.  The GNU extension of allowing the user
     to provide their own directory handling and ‘stat’ functions
     complicates things a bit.  If these callback functions are used and
     a large file or directory is encountered ‘glob’ _can_ fail.

 -- Function: int glob64 (const char *PATTERN, int FLAGS, int (*ERRFUNC)
          (const char *FILENAME, int ERROR-CODE), glob64_t *VECTOR-PTR)

     Preliminary: | MT-Unsafe race:utent env sig:ALRM timer locale |
     AS-Unsafe dlopen corrupt heap lock | AC-Unsafe corrupt lock fd mem
     | *Note POSIX Safety Concepts::.

     The ‘glob64’ function was added as part of the Large File Summit
     extensions but is not part of the original LFS proposal.  The
     reason for this is simple: it is not necessary.  The necessity for
     a ‘glob64’ function is added by the extensions of the GNU ‘glob’
     implementation which allows the user to provide their own directory
     handling and ‘stat’ functions.  The ‘readdir’ and ‘stat’ functions
     do depend on the choice of ‘_FILE_OFFSET_BITS’ since the definition
     of the types ‘struct dirent’ and ‘struct stat’ will change
     depending on the choice.

     Besides this difference, ‘glob64’ works just like ‘glob’ in all
     aspects.

     This function is a GNU extension.


File: libc.info,  Node: Flags for Globbing,  Next: More Flags for Globbing,  Prev: Calling Glob,  Up: Globbing

10.2.2 Flags for Globbing
-------------------------

This section describes the standard flags that you can specify in the
FLAGS argument to ‘glob’.  Choose the flags you want, and combine them
with the C bitwise OR operator ‘|’.

   Note that there are *note More Flags for Globbing:: available as GNU
extensions.

‘GLOB_APPEND’

     Append the words from this expansion to the vector of words
     produced by previous calls to ‘glob’.  This way you can effectively
     expand several words as if they were concatenated with spaces
     between them.

     In order for appending to work, you must not modify the contents of
     the word vector structure between calls to ‘glob’.  And, if you set
     ‘GLOB_DOOFFS’ in the first call to ‘glob’, you must also set it
     when you append to the results.

     Note that the pointer stored in ‘gl_pathv’ may no longer be valid
     after you call ‘glob’ the second time, because ‘glob’ might have
     relocated the vector.  So always fetch ‘gl_pathv’ from the ‘glob_t’
     structure after each ‘glob’ call; *never* save the pointer across
     calls.

‘GLOB_DOOFFS’

     Leave blank slots at the beginning of the vector of words.  The
     ‘gl_offs’ field says how many slots to leave.  The blank slots
     contain null pointers.

‘GLOB_ERR’

     Give up right away and report an error if there is any difficulty
     reading the directories that must be read in order to expand
     PATTERN fully.  Such difficulties might include a directory in
     which you don't have the requisite access.  Normally, ‘glob’ tries
     its best to keep on going despite any errors, reading whatever
     directories it can.

     You can exercise even more control than this by specifying an
     error-handler function ERRFUNC when you call ‘glob’.  If ERRFUNC is
     not a null pointer, then ‘glob’ doesn't give up right away when it
     can't read a directory; instead, it calls ERRFUNC with two
     arguments, like this:

          (*ERRFUNC) (FILENAME, ERROR-CODE)

     The argument FILENAME is the name of the directory that ‘glob’
     couldn't open or couldn't read, and ERROR-CODE is the ‘errno’ value
     that was reported to ‘glob’.

     If the error handler function returns nonzero, then ‘glob’ gives up
     right away.  Otherwise, it continues.

‘GLOB_MARK’

     If the pattern matches the name of a directory, append ‘/’ to the
     directory's name when returning it.

‘GLOB_NOCHECK’

     If the pattern doesn't match any file names, return the pattern
     itself as if it were a file name that had been matched.  (Normally,
     when the pattern doesn't match anything, ‘glob’ returns that there
     were no matches.)

‘GLOB_NOESCAPE’

     Don't treat the ‘\’ character specially in patterns.  Normally, ‘\’
     quotes the following character, turning off its special meaning (if
     any) so that it matches only itself.  When quoting is enabled, the
     pattern ‘\?’ matches only the string ‘?’, because the question mark
     in the pattern acts like an ordinary character.

     If you use ‘GLOB_NOESCAPE’, then ‘\’ is an ordinary character.

     ‘glob’ does its work by calling the function ‘fnmatch’ repeatedly.
     It handles the flag ‘GLOB_NOESCAPE’ by turning on the
     ‘FNM_NOESCAPE’ flag in calls to ‘fnmatch’.

‘GLOB_NOSORT’

     Don't sort the file names; return them in no particular order.  (In
     practice, the order will depend on the order of the entries in the
     directory.)  The only reason _not_ to sort is to save time.


File: libc.info,  Node: More Flags for Globbing,  Prev: Flags for Globbing,  Up: Globbing

10.2.3 More Flags for Globbing
------------------------------

Beside the flags described in the last section, the GNU implementation
of ‘glob’ allows a few more flags which are also defined in the ‘glob.h’
file.  Some of the extensions implement functionality which is available
in modern shell implementations.

‘GLOB_PERIOD’

     The ‘.’ character (period) is treated special.  It cannot be
     matched by wildcards.  *Note Wildcard Matching::, ‘FNM_PERIOD’.

‘GLOB_MAGCHAR’

     The ‘GLOB_MAGCHAR’ value is not to be given to ‘glob’ in the FLAGS
     parameter.  Instead, ‘glob’ sets this bit in the GL_FLAGS element
     of the GLOB_T structure provided as the result if the pattern used
     for matching contains any wildcard character.

‘GLOB_ALTDIRFUNC’

     Instead of using the normal functions for accessing the filesystem
     the ‘glob’ implementation uses the user-supplied functions
     specified in the structure pointed to by PGLOB parameter.  For more
     information about the functions refer to the sections about
     directory handling see *note Accessing Directories::, and *note
     Reading Attributes::.

‘GLOB_BRACE’

     If this flag is given, the handling of braces in the pattern is
     changed.  It is now required that braces appear correctly grouped.
     I.e., for each opening brace there must be a closing one.  Braces
     can be used recursively.  So it is possible to define one brace
     expression in another one.  It is important to note that the range
     of each brace expression is completely contained in the outer brace
     expression (if there is one).

     The string between the matching braces is separated into single
     expressions by splitting at ‘,’ (comma) characters.  The commas
     themselves are discarded.  Please note what we said above about
     recursive brace expressions.  The commas used to separate the
     subexpressions must be at the same level.  Commas in brace
     subexpressions are not matched.  They are used during expansion of
     the brace expression of the deeper level.  The example below shows
     this

          glob ("{foo/{,bar,biz},baz}", GLOB_BRACE, NULL, &result)

     is equivalent to the sequence

          glob ("foo/", GLOB_BRACE, NULL, &result)
          glob ("foo/bar", GLOB_BRACE|GLOB_APPEND, NULL, &result)
          glob ("foo/biz", GLOB_BRACE|GLOB_APPEND, NULL, &result)
          glob ("baz", GLOB_BRACE|GLOB_APPEND, NULL, &result)

     if we leave aside error handling.

‘GLOB_NOMAGIC’

     If the pattern contains no wildcard constructs (it is a literal
     file name), return it as the sole "matching" word, even if no file
     exists by that name.

‘GLOB_TILDE’

     If this flag is used the character ‘~’ (tilde) is handled specially
     if it appears at the beginning of the pattern.  Instead of being
     taken verbatim it is used to represent the home directory of a
     known user.

     If ‘~’ is the only character in pattern or it is followed by a ‘/’
     (slash), the home directory of the process owner is substituted.
     Using ‘getlogin’ and ‘getpwnam’ the information is read from the
     system databases.  As an example take user ‘bart’ with his home
     directory at ‘/home/bart’.  For him a call like

          glob ("~/bin/*", GLOB_TILDE, NULL, &result)

     would return the contents of the directory ‘/home/bart/bin’.
     Instead of referring to the own home directory it is also possible
     to name the home directory of other users.  To do so one has to
     append the user name after the tilde character.  So the contents of
     user ‘homer’'s ‘bin’ directory can be retrieved by

          glob ("~homer/bin/*", GLOB_TILDE, NULL, &result)

     If the user name is not valid or the home directory cannot be
     determined for some reason the pattern is left untouched and itself
     used as the result.  I.e., if in the last example ‘home’ is not
     available the tilde expansion yields to ‘"~homer/bin/*"’ and ‘glob’
     is not looking for a directory named ‘~homer’.

     This functionality is equivalent to what is available in C-shells
     if the ‘nonomatch’ flag is set.

‘GLOB_TILDE_CHECK’

     If this flag is used ‘glob’ behaves as if ‘GLOB_TILDE’ is given.
     The only difference is that if the user name is not available or
     the home directory cannot be determined for other reasons this
     leads to an error.  ‘glob’ will return ‘GLOB_NOMATCH’ instead of
     using the pattern itself as the name.

     This functionality is equivalent to what is available in C-shells
     if the ‘nonomatch’ flag is not set.

‘GLOB_ONLYDIR’

     If this flag is used the globbing function takes this as a *hint*
     that the caller is only interested in directories matching the
     pattern.  If the information about the type of the file is easily
     available non-directories will be rejected but no extra work will
     be done to determine the information for each file.  I.e., the
     caller must still be able to filter directories out.

     This functionality is only available with the GNU ‘glob’
     implementation.  It is mainly used internally to increase the
     performance but might be useful for a user as well and therefore is
     documented here.

   Calling ‘glob’ will in most cases allocate resources which are used
to represent the result of the function call.  If the same object of
type ‘glob_t’ is used in multiple call to ‘glob’ the resources are freed
or reused so that no leaks appear.  But this does not include the time
when all ‘glob’ calls are done.

 -- Function: void globfree (glob_t *PGLOB)

     Preliminary: | MT-Safe | AS-Unsafe corrupt heap | AC-Unsafe corrupt
     mem | *Note POSIX Safety Concepts::.

     The ‘globfree’ function frees all resources allocated by previous
     calls to ‘glob’ associated with the object pointed to by PGLOB.
     This function should be called whenever the currently used ‘glob_t’
     typed object isn't used anymore.

 -- Function: void globfree64 (glob64_t *PGLOB)

     Preliminary: | MT-Safe | AS-Unsafe corrupt lock | AC-Unsafe corrupt
     lock fd mem | *Note POSIX Safety Concepts::.

     This function is equivalent to ‘globfree’ but it frees records of
     type ‘glob64_t’ which were allocated by ‘glob64’.


File: libc.info,  Node: Regular Expressions,  Next: Word Expansion,  Prev: Globbing,  Up: Pattern Matching

10.3 Regular Expression Matching
================================

The GNU C Library supports two interfaces for matching regular
expressions.  One is the standard POSIX.2 interface, and the other is
what the GNU C Library has had for many years.

   Both interfaces are declared in the header file ‘regex.h’.  If you
define ‘_POSIX_C_SOURCE’, then only the POSIX.2 functions, structures,
and constants are declared.

* Menu:

* POSIX Regexp Compilation::    Using ‘regcomp’ to prepare to match.
* Flags for POSIX Regexps::     Syntax variations for ‘regcomp’.
* Matching POSIX Regexps::      Using ‘regexec’ to match the compiled
				   pattern that you get from ‘regcomp’.
* Regexp Subexpressions::       Finding which parts of the string were matched.
* Subexpression Complications:: Find points of which parts were matched.
* Regexp Cleanup::		Freeing storage; reporting errors.


File: libc.info,  Node: POSIX Regexp Compilation,  Next: Flags for POSIX Regexps,  Up: Regular Expressions

10.3.1 POSIX Regular Expression Compilation
-------------------------------------------

Before you can actually match a regular expression, you must “compile”
it.  This is not true compilation--it produces a special data structure,
not machine instructions.  But it is like ordinary compilation in that
its purpose is to enable you to "execute" the pattern fast.  (*Note
Matching POSIX Regexps::, for how to use the compiled regular expression
for matching.)

   There is a special data type for compiled regular expressions:

 -- Data Type: regex_t

     This type of object holds a compiled regular expression.  It is
     actually a structure.  It has just one field that your programs
     should look at:

     ‘re_nsub’
          This field holds the number of parenthetical subexpressions in
          the regular expression that was compiled.

     There are several other fields, but we don't describe them here,
     because only the functions in the library should use them.

   After you create a ‘regex_t’ object, you can compile a regular
expression into it by calling ‘regcomp’.

 -- Function: int regcomp (regex_t *restrict COMPILED, const char
          *restrict PATTERN, int CFLAGS)

     Preliminary: | MT-Safe locale | AS-Unsafe corrupt heap lock dlopen
     | AC-Unsafe corrupt lock mem fd | *Note POSIX Safety Concepts::.

     The function ‘regcomp’ "compiles" a regular expression into a data
     structure that you can use with ‘regexec’ to match against a
     string.  The compiled regular expression format is designed for
     efficient matching.  ‘regcomp’ stores it into ‘*COMPILED’.

     It's up to you to allocate an object of type ‘regex_t’ and pass its
     address to ‘regcomp’.

     The argument CFLAGS lets you specify various options that control
     the syntax and semantics of regular expressions.  *Note Flags for
     POSIX Regexps::.

     If you use the flag ‘REG_NOSUB’, then ‘regcomp’ omits from the
     compiled regular expression the information necessary to record how
     subexpressions actually match.  In this case, you might as well
     pass ‘0’ for the MATCHPTR and NMATCH arguments when you call
     ‘regexec’.

     If you don't use ‘REG_NOSUB’, then the compiled regular expression
     does have the capacity to record how subexpressions match.  Also,
     ‘regcomp’ tells you how many subexpressions PATTERN has, by storing
     the number in ‘COMPILED->re_nsub’.  You can use that value to
     decide how long an array to allocate to hold information about
     subexpression matches.

     ‘regcomp’ returns ‘0’ if it succeeds in compiling the regular
     expression; otherwise, it returns a nonzero error code (see the
     table below).  You can use ‘regerror’ to produce an error message
     string describing the reason for a nonzero value; see *note Regexp
     Cleanup::.

   Here are the possible nonzero values that ‘regcomp’ can return:

‘REG_BADBR’

     There was an invalid ‘\{...\}’ construct in the regular expression.
     A valid ‘\{...\}’ construct must contain either a single number, or
     two numbers in increasing order separated by a comma.

‘REG_BADPAT’

     There was a syntax error in the regular expression.

‘REG_BADRPT’

     A repetition operator such as ‘?’ or ‘*’ appeared in a bad position
     (with no preceding subexpression to act on).

‘REG_ECOLLATE’

     The regular expression referred to an invalid collating element
     (one not defined in the current locale for string collation).
     *Note Locale Categories::.

‘REG_ECTYPE’

     The regular expression referred to an invalid character class name.

‘REG_EESCAPE’

     The regular expression ended with ‘\’.

‘REG_ESUBREG’

     There was an invalid number in the ‘\DIGIT’ construct.

‘REG_EBRACK’

     There were unbalanced square brackets in the regular expression.

‘REG_EPAREN’

     An extended regular expression had unbalanced parentheses, or a
     basic regular expression had unbalanced ‘\(’ and ‘\)’.

‘REG_EBRACE’

     The regular expression had unbalanced ‘\{’ and ‘\}’.

‘REG_ERANGE’

     One of the endpoints in a range expression was invalid.

‘REG_ESPACE’

     ‘regcomp’ ran out of memory.


File: libc.info,  Node: Flags for POSIX Regexps,  Next: Matching POSIX Regexps,  Prev: POSIX Regexp Compilation,  Up: Regular Expressions

10.3.2 Flags for POSIX Regular Expressions
------------------------------------------

These are the bit flags that you can use in the CFLAGS operand when
compiling a regular expression with ‘regcomp’.

‘REG_EXTENDED’

     Treat the pattern as an extended regular expression, rather than as
     a basic regular expression.

‘REG_ICASE’

     Ignore case when matching letters.

‘REG_NOSUB’

     Don't bother storing the contents of the MATCHPTR array.

‘REG_NEWLINE’

     Treat a newline in STRING as dividing STRING into multiple lines,
     so that ‘$’ can match before the newline and ‘^’ can match after.
     Also, don't permit ‘.’ to match a newline, and don't permit
     ‘[^...]’ to match a newline.

     Otherwise, newline acts like any other ordinary character.


File: libc.info,  Node: Matching POSIX Regexps,  Next: Regexp Subexpressions,  Prev: Flags for POSIX Regexps,  Up: Regular Expressions

10.3.3 Matching a Compiled POSIX Regular Expression
---------------------------------------------------

Once you have compiled a regular expression, as described in *note POSIX
Regexp Compilation::, you can match it against strings using ‘regexec’.
A match anywhere inside the string counts as success, unless the regular
expression contains anchor characters (‘^’ or ‘$’).

 -- Function: int regexec (const regex_t *restrict COMPILED, const char
          *restrict STRING, size_t NMATCH, regmatch_t
          MATCHPTR[restrict], int EFLAGS)

     Preliminary: | MT-Safe locale | AS-Unsafe corrupt heap lock dlopen
     | AC-Unsafe corrupt lock mem fd | *Note POSIX Safety Concepts::.

     This function tries to match the compiled regular expression
     ‘*COMPILED’ against STRING.

     ‘regexec’ returns ‘0’ if the regular expression matches; otherwise,
     it returns a nonzero value.  See the table below for what nonzero
     values mean.  You can use ‘regerror’ to produce an error message
     string describing the reason for a nonzero value; see *note Regexp
     Cleanup::.

     The argument EFLAGS is a word of bit flags that enable various
     options.

     If you want to get information about what part of STRING actually
     matched the regular expression or its subexpressions, use the
     arguments MATCHPTR and NMATCH.  Otherwise, pass ‘0’ for NMATCH, and
     ‘NULL’ for MATCHPTR.  *Note Regexp Subexpressions::.

   You must match the regular expression with the same set of current
locales that were in effect when you compiled the regular expression.

   The function ‘regexec’ accepts the following flags in the EFLAGS
argument:

‘REG_NOTBOL’

     Do not regard the beginning of the specified string as the
     beginning of a line; more generally, don't make any assumptions
     about what text might precede it.

‘REG_NOTEOL’

     Do not regard the end of the specified string as the end of a line;
     more generally, don't make any assumptions about what text might
     follow it.

   Here are the possible nonzero values that ‘regexec’ can return:

‘REG_NOMATCH’

     The pattern didn't match the string.  This isn't really an error.

‘REG_ESPACE’

     ‘regexec’ ran out of memory.


File: libc.info,  Node: Regexp Subexpressions,  Next: Subexpression Complications,  Prev: Matching POSIX Regexps,  Up: Regular Expressions

10.3.4 Match Results with Subexpressions
----------------------------------------

When ‘regexec’ matches parenthetical subexpressions of PATTERN, it
records which parts of STRING they match.  It returns that information
by storing the offsets into an array whose elements are structures of
type ‘regmatch_t’.  The first element of the array (index ‘0’) records
the part of the string that matched the entire regular expression.  Each
other element of the array records the beginning and end of the part
that matched a single parenthetical subexpression.

 -- Data Type: regmatch_t

     This is the data type of the MATCHPTR array that you pass to
     ‘regexec’.  It contains two structure fields, as follows:

     ‘rm_so’
          The offset in STRING of the beginning of a substring.  Add
          this value to STRING to get the address of that part.

     ‘rm_eo’
          The offset in STRING of the end of the substring.

 -- Data Type: regoff_t

     ‘regoff_t’ is an alias for another signed integer type.  The fields
     of ‘regmatch_t’ have type ‘regoff_t’.

   The ‘regmatch_t’ elements correspond to subexpressions positionally;
the first element (index ‘1’) records where the first subexpression
matched, the second element records the second subexpression, and so on.
The order of the subexpressions is the order in which they begin.

   When you call ‘regexec’, you specify how long the MATCHPTR array is,
with the NMATCH argument.  This tells ‘regexec’ how many elements to
store.  If the actual regular expression has more than NMATCH
subexpressions, then you won't get offset information about the rest of
them.  But this doesn't alter whether the pattern matches a particular
string or not.

   If you don't want ‘regexec’ to return any information about where the
subexpressions matched, you can either supply ‘0’ for NMATCH, or use the
flag ‘REG_NOSUB’ when you compile the pattern with ‘regcomp’.


File: libc.info,  Node: Subexpression Complications,  Next: Regexp Cleanup,  Prev: Regexp Subexpressions,  Up: Regular Expressions

10.3.5 Complications in Subexpression Matching
----------------------------------------------

Sometimes a subexpression matches a substring of no characters.  This
happens when ‘f\(o*\)’ matches the string ‘fum’.  (It really matches
just the ‘f’.)  In this case, both of the offsets identify the point in
the string where the null substring was found.  In this example, the
offsets are both ‘1’.

   Sometimes the entire regular expression can match without using some
of its subexpressions at all--for example, when ‘ba\(na\)*’ matches the
string ‘ba’, the parenthetical subexpression is not used.  When this
happens, ‘regexec’ stores ‘-1’ in both fields of the element for that
subexpression.

   Sometimes matching the entire regular expression can match a
particular subexpression more than once--for example, when ‘ba\(na\)*’
matches the string ‘bananana’, the parenthetical subexpression matches
three times.  When this happens, ‘regexec’ usually stores the offsets of
the last part of the string that matched the subexpression.  In the case
of ‘bananana’, these offsets are ‘6’ and ‘8’.

   But the last match is not always the one that is chosen.  It's more
accurate to say that the last _opportunity_ to match is the one that
takes precedence.  What this means is that when one subexpression
appears within another, then the results reported for the inner
subexpression reflect whatever happened on the last match of the outer
subexpression.  For an example, consider ‘\(ba\(na\)*s \)*’ matching the
string ‘bananas bas ’.  The last time the inner expression actually
matches is near the end of the first word.  But it is _considered_ again
in the second word, and fails to match there.  ‘regexec’ reports nonuse
of the "na" subexpression.

   Another place where this rule applies is when the regular expression
     \(ba\(na\)*s \|nefer\(ti\)* \)*
matches ‘bananas nefertiti’.  The "na" subexpression does match in the
first word, but it doesn't match in the second word because the other
alternative is used there.  Once again, the second repetition of the
outer subexpression overrides the first, and within that second
repetition, the "na" subexpression is not used.  So ‘regexec’ reports
nonuse of the "na" subexpression.


File: libc.info,  Node: Regexp Cleanup,  Prev: Subexpression Complications,  Up: Regular Expressions

10.3.6 POSIX Regexp Matching Cleanup
------------------------------------

When you are finished using a compiled regular expression, you can free
the storage it uses by calling ‘regfree’.

 -- Function: void regfree (regex_t *COMPILED)

     Preliminary: | MT-Safe | AS-Unsafe heap | AC-Unsafe mem | *Note
     POSIX Safety Concepts::.

     Calling ‘regfree’ frees all the storage that ‘*COMPILED’ points to.
     This includes various internal fields of the ‘regex_t’ structure
     that aren't documented in this manual.

     ‘regfree’ does not free the object ‘*COMPILED’ itself.

   You should always free the space in a ‘regex_t’ structure with
‘regfree’ before using the structure to compile another regular
expression.

   When ‘regcomp’ or ‘regexec’ reports an error, you can use the
function ‘regerror’ to turn it into an error message string.

 -- Function: size_t regerror (int ERRCODE, const regex_t *restrict
          COMPILED, char *restrict BUFFER, size_t LENGTH)

     Preliminary: | MT-Safe env | AS-Unsafe corrupt heap lock dlopen |
     AC-Unsafe corrupt lock fd mem | *Note POSIX Safety Concepts::.

     This function produces an error message string for the error code
     ERRCODE, and stores the string in LENGTH bytes of memory starting
     at BUFFER.  For the COMPILED argument, supply the same compiled
     regular expression structure that ‘regcomp’ or ‘regexec’ was
     working with when it got the error.  Alternatively, you can supply
     ‘NULL’ for COMPILED; you will still get a meaningful error message,
     but it might not be as detailed.

     If the error message can't fit in LENGTH bytes (including a
     terminating null character), then ‘regerror’ truncates it.  The
     string that ‘regerror’ stores is always null-terminated even if it
     has been truncated.

     The return value of ‘regerror’ is the minimum length needed to
     store the entire error message.  If this is less than LENGTH, then
     the error message was not truncated, and you can use it.
     Otherwise, you should call ‘regerror’ again with a larger buffer.

     Here is a function which uses ‘regerror’, but always dynamically
     allocates a buffer for the error message:

          char *get_regerror (int errcode, regex_t *compiled)
          {
            size_t length = regerror (errcode, compiled, NULL, 0);
            char *buffer = xmalloc (length);
            (void) regerror (errcode, compiled, buffer, length);
            return buffer;
          }


File: libc.info,  Node: Word Expansion,  Prev: Regular Expressions,  Up: Pattern Matching

10.4 Shell-Style Word Expansion
===============================

“Word expansion” means the process of splitting a string into “words”
and substituting for variables, commands, and wildcards just as the
shell does.

   For example, when you write ‘ls -l foo.c’, this string is split into
three separate words--‘ls’, ‘-l’ and ‘foo.c’.  This is the most basic
function of word expansion.

   When you write ‘ls *.c’, this can become many words, because the word
‘*.c’ can be replaced with any number of file names.  This is called
“wildcard expansion”, and it is also a part of word expansion.

   When you use ‘echo $PATH’ to print your path, you are taking
advantage of “variable substitution”, which is also part of word
expansion.

   Ordinary programs can perform word expansion just like the shell by
calling the library function ‘wordexp’.

* Menu:

* Expansion Stages::            What word expansion does to a string.
* Calling Wordexp::             How to call ‘wordexp’.
* Flags for Wordexp::           Options you can enable in ‘wordexp’.
* Wordexp Example::             A sample program that does word expansion.
* Tilde Expansion::             Details of how tilde expansion works.
* Variable Substitution::       Different types of variable substitution.


File: libc.info,  Node: Expansion Stages,  Next: Calling Wordexp,  Up: Word Expansion

10.4.1 The Stages of Word Expansion
-----------------------------------

When word expansion is applied to a sequence of words, it performs the
following transformations in the order shown here:

  1. “Tilde expansion”: Replacement of ‘~foo’ with the name of the home
     directory of ‘foo’.

  2. Next, three different transformations are applied in the same step,
     from left to right:

        • “Variable substitution”: Environment variables are substituted
          for references such as ‘$foo’.

        • “Command substitution”: Constructs such as ‘`cat foo`’ and the
          equivalent ‘$(cat foo)’ are replaced with the output from the
          inner command.

        • “Arithmetic expansion”: Constructs such as ‘$(($x-1))’ are
          replaced with the result of the arithmetic computation.

  3. “Field splitting”: subdivision of the text into “words”.

  4. “Wildcard expansion”: The replacement of a construct such as ‘*.c’
     with a list of ‘.c’ file names.  Wildcard expansion applies to an
     entire word at a time, and replaces that word with 0 or more file
     names that are themselves words.

  5. “Quote removal”: The deletion of string-quotes, now that they have
     done their job by inhibiting the above transformations when
     appropriate.

   For the details of these transformations, and how to write the
constructs that use them, see ‘The BASH Manual’ (to appear).


File: libc.info,  Node: Calling Wordexp,  Next: Flags for Wordexp,  Prev: Expansion Stages,  Up: Word Expansion

10.4.2 Calling ‘wordexp’
------------------------

All the functions, constants and data types for word expansion are
declared in the header file ‘wordexp.h’.

   Word expansion produces a vector of words (strings).  To return this
vector, ‘wordexp’ uses a special data type, ‘wordexp_t’, which is a
structure.  You pass ‘wordexp’ the address of the structure, and it
fills in the structure's fields to tell you about the results.

 -- Data Type: wordexp_t

     This data type holds a pointer to a word vector.  More precisely,
     it records both the address of the word vector and its size.

     ‘we_wordc’
          The number of elements in the vector.

     ‘we_wordv’
          The address of the vector.  This field has type ‘char **’.

     ‘we_offs’
          The offset of the first real element of the vector, from its
          nominal address in the ‘we_wordv’ field.  Unlike the other
          fields, this is always an input to ‘wordexp’, rather than an
          output from it.

          If you use a nonzero offset, then that many elements at the
          beginning of the vector are left empty.  (The ‘wordexp’
          function fills them with null pointers.)

          The ‘we_offs’ field is meaningful only if you use the
          ‘WRDE_DOOFFS’ flag.  Otherwise, the offset is always zero
          regardless of what is in this field, and the first real
          element comes at the beginning of the vector.

 -- Function: int wordexp (const char *WORDS, wordexp_t
          *WORD-VECTOR-PTR, int FLAGS)

     Preliminary: | MT-Unsafe race:utent const:env env sig:ALRM timer
     locale | AS-Unsafe dlopen plugin i18n heap corrupt lock | AC-Unsafe
     corrupt lock fd mem | *Note POSIX Safety Concepts::.

     Perform word expansion on the string WORDS, putting the result in a
     newly allocated vector, and store the size and address of this
     vector into ‘*WORD-VECTOR-PTR’.  The argument FLAGS is a
     combination of bit flags; see *note Flags for Wordexp::, for
     details of the flags.

     You shouldn't use any of the characters ‘|&;<>’ in the string WORDS
     unless they are quoted; likewise for newline.  If you use these
     characters unquoted, you will get the ‘WRDE_BADCHAR’ error code.
     Don't use parentheses or braces unless they are quoted or part of a
     word expansion construct.  If you use quotation characters ‘'"`’,
     they should come in pairs that balance.

     The results of word expansion are a sequence of words.  The
     function ‘wordexp’ allocates a string for each resulting word, then
     allocates a vector of type ‘char **’ to store the addresses of
     these strings.  The last element of the vector is a null pointer.
     This vector is called the “word vector”.

     To return this vector, ‘wordexp’ stores both its address and its
     length (number of elements, not counting the terminating null
     pointer) into ‘*WORD-VECTOR-PTR’.

     If ‘wordexp’ succeeds, it returns 0.  Otherwise, it returns one of
     these error codes:

     ‘WRDE_BADCHAR’

          The input string WORDS contains an unquoted invalid character
          such as ‘|’.

     ‘WRDE_BADVAL’

          The input string refers to an undefined shell variable, and
          you used the flag ‘WRDE_UNDEF’ to forbid such references.

     ‘WRDE_CMDSUB’

          The input string uses command substitution, and you used the
          flag ‘WRDE_NOCMD’ to forbid command substitution.

     ‘WRDE_NOSPACE’

          It was impossible to allocate memory to hold the result.  In
          this case, ‘wordexp’ can store part of the results--as much as
          it could allocate room for.

     ‘WRDE_SYNTAX’

          There was a syntax error in the input string.  For example, an
          unmatched quoting character is a syntax error.  This error
          code is also used to signal division by zero and overflow in
          arithmetic expansion.

 -- Function: void wordfree (wordexp_t *WORD-VECTOR-PTR)

     Preliminary: | MT-Safe | AS-Unsafe corrupt heap | AC-Unsafe corrupt
     mem | *Note POSIX Safety Concepts::.

     Free the storage used for the word-strings and vector that
     ‘*WORD-VECTOR-PTR’ points to.  This does not free the structure
     ‘*WORD-VECTOR-PTR’ itself--only the other data it points to.