'\" t .\"*************************************************************************** .\" Copyright 2018-2024,2025 Thomas E. Dickey * .\" Copyright 1998-2016,2017 Free Software Foundation, Inc. * .\" * .\" Permission is hereby granted, free of charge, to any person obtaining a * .\" copy of this software and associated documentation files (the * .\" "Software"), to deal in the Software without restriction, including * .\" without limitation the rights to use, copy, modify, merge, publish, * .\" distribute, distribute with modifications, sublicense, and/or sell * .\" copies of the Software, and to permit persons to whom the Software is * .\" furnished to do so, subject to the following conditions: * .\" * .\" The above copyright notice and this permission notice shall be included * .\" in all copies or substantial portions of the Software. * .\" * .\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * .\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * .\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * .\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, * .\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR * .\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR * .\" THE USE OR OTHER DEALINGS IN THE SOFTWARE. * .\" * .\" Except as contained in this notice, the name(s) of the above copyright * .\" holders shall not be used in advertising or otherwise to promote the * .\" sale, use or other dealings in this Software without prior written * .\" authorization. * .\"*************************************************************************** .\" .\" $Id: curs_getch.3x,v 1.130 2025/07/05 13:06:45 tom Exp $ .TH curs_getch 3X 2025-07-05 "ncurses 6.5" "Library calls" .ie \n(.g \{\ .ds `` \(lq .ds '' \(rq .ds ^ \(ha .\} .el \{\ .ie t .ds `` `` .el .ds `` "" .ie t .ds '' '' .el .ds '' "" .ds ^ ^ .\} . .ie \n(.g .ds : \: .el .ds : \" empty . .de bP .ie n .IP \(bu 4 .el .IP \(bu 2 .. .SH NAME \fB\%getch\fP, \fB\%wgetch\fP, \fB\%mvgetch\fP, \fB\%mvwgetch\fP, \fB\%ungetch\fP, \fB\%has_key\fP \- get (or push back) characters from \fIcurses\fR terminal keyboard buffer .SH SYNOPSIS .nf .B #include .PP .B int getch(void); .B int wgetch(WINDOW * \fIwin\fP); .B int mvgetch(int \fIy\fP, int \fIx\fP); .B int mvwgetch(WINDOW * \fIwin\fP, int \fIy\fP, int \fIx\fP); .PP .B int ungetch(int \fIc\fP); .PP .\" XXX: Move has_key into its own page like define_key and key_defined? \fI/* extension */\fP .B int has_key(int \fIc\fP); .fi .SH DESCRIPTION .SS "Reading Characters" .B \%wgetch gathers a key event from the terminal keyboard associated with a .I curses window .IR win "." \fB\%ncurses\fP(3X) describes the variants of this function. .PP When input is pending, .B \%wgetch returns an integer identifying the key event; for alphanumeric and punctuation keys, the space bar, and (usually) the Backspace, Tab, Return, and Escape keys, this value corresponds to the character encoding used by the terminal. Use of the control key as a modifier, by holding it down while pressing and releasing another key, often results in a distinct code. The behavior of other keys depends on whether .I win is in keypad mode; see subsection \*(``Keypad Mode\*('' below. .PP If no input is pending, then if the no-delay flag is set in the window (see \fB\%nodelay\fP(3X)), the function returns .BR ERR ";" otherwise, .I curses waits until the terminal has input. If \fB\%cbreak\fP(3X) or \fB\%raw\fP(3X) has been called, this happens after .I curses reads one key event. If \fB\%nocbreak\fP(3X) or \fB\%noraw\fP(3X) has been called, it occurs when .I curses reads a newline. \" "newline" because canonical mode normalizes NL/CR (Because the terminal's canonical or \*(``cooked\*('' mode is line-buffered, multiple .B \%wgetch calls may then be necessary to empty the input queue.) If \fB\%halfdelay\fP(3X) has been called, .I curses waits until input is available or the specified delay elapses. .PP If \fB\%echo\fP(3X) has been called, and the window is not a pad, .I curses writes the returned character .I c to the window (at the cursor position) per the following rules. .bP If .I c matches the terminal's erase character (see \fB\%erasechar\fP(3X)), and the cursor is not at the window's leftmost column, the cursor moves leftward one position and the new position is erased as if \fB\%wmove\fP(3X) and then \fB\%wdelch\fP(3X) were called. When the window's keypad mode is enabled (see below), .B \%KEY_LEFT and .B \%KEY_BACKSPACE are handled the same way. .bP .I curses writes any other .I c to the window, as with \fB\%wechochar\fP(3X). .bP If the window .I win has been moved or modified since the last call to \fB\%wrefresh\fP(3X), .I curses calls .B \%wrefresh on it. .PP If .I c is a carriage return and \fBnl\fP(3X) has been called, .B \%wgetch returns the character code for line feed instead. .SS "Keypad Mode" Call \fB\%keypad\fP(3X) on a window to configure keypad mode when reading input from it. In .IR "keypad mode" "," .I curses treats key strokes not from the alphabetic section of the keyboard (those corresponding to the ECMA-6 character set \(em see \fI\%ascii\fP(7) \(em optionally modified by either the control or shift keys) as .I function keys. (In .IR curses "," the term \*(``function key\*('' includes but is not limited to keycaps engraved with \*(``F1\*('', \*(``PF1\*('', and so on.) If a window is in keypad mode, .B \%wgetch translates these key strokes to a numeric code corresponding to the .B KEY_ symbols listed in subsection \*(``Predefined Key Codes\*('' below. If the window is not in keypad mode, the input queue populates with the characters of the function key's escape sequence, which the application must collect individually with multiple .B \%wgetch calls. .bP The .I \%curses.h header file declares many .I "predefined function keys" whose names begin with .BR KEY_ ";" these object-like macros have integer values outside the range of eight-bit character codes. .bP In .IR \%ncurses "," .I "user-defined function keys" are configured with \fB\%define_key\fP(3X); they have no names, but are also expected to have integer values outside the range of eight-bit character codes. .PP A variable intended to hold a function key code must thus be of type .I short or larger. .PP Most terminals one encounters follow the ECMA-48 standard insofar as their function keys produce character sequences prefixed with the escape character ESC. This fact implies that .I curses cannot distinguish a user's press of the escape key (assuming it sends ESC) from the beginning of a function key's character sequence without waiting to see if, and how soon, further input arrives. .bP If the escape sequence matches a string capability defining a function key for the terminal type (such as .B \%key_home .RB \%( khome ) or .B \%key_up .RB \%( kuu1 )), .B \%wgetch returns the function key code corresponding to the unique sequence defined by the terminal. .bP If the escape sequence matches no function keys defined for the terminal type, call .B \%wgetch repeatedly to obtain the codes of the individual characters of the sequence, in the order they occurred in the input. .bP If .B \%wgetch cannot decide the validity of the input as a function key because it has not read enough characters to disambiguate it, the function waits until it has this information or the .I "escape delay" elapses. Configure the escape delay with the global variable .BR \%ESCDELAY "," an extension (see section \*(``EXTENSIONS\*('' below), or the environment variable of the same name (see section \*(``ENVIRONMENT\*('' of \fB\%ncurses\fP(3X)), also an extension. .PP Consequently, a user of a .I curses application that employs keypad mode may experience a pause or \*(``hang\*('' after pressing the escape key while .I curses collects sufficient characters to disambiguate the input. If the window is in \*(``no time-out\*('' mode, the escape delay is effectively infinite; see \fB\%notimeout\fP(3X). In the event of such a pause, further typing \*(``awakens\*('' .IR curses "." .SS "Ungetting Characters" .B \%ungetch places .I c into the input queue to be returned by the next call to .BR \%wgetch "." A single input queue serves all windows associated with the screen. .SS "Predefined Key Codes" The header file .I \%curses.h defines the following function key codes. .bP Except for the special case of .BR \%KEY_RESIZE "," a window's keypad mode must be enabled for .B \%wgetch to read these codes from it. .bP Not all of these are necessarily supported on any particular terminal. .bP The naming convention may seem obscure, with some apparent misspellings (such as \*(``RSUME\*('' for \*(``resume\*(''); the names correspond to the .I \%term\%info capability names for the keys, and were standardized before the IBM PC/AT keyboard layout achieved a dominant position in industry. .PP .RS .\" XXX: Move this list into ncurses(3X), rather than duplicating it in .\" get_wch(3X) or having that page cross reference this one? .TS Lb Lb Lb Lx. Symbol Key name = KEY_BREAK Break key .ne 4 KEY_DOWN Arrow keys KEY_UP \^ KEY_LEFT \^ KEY_RIGHT \^ KEY_HOME Home key (upward+left arrow) KEY_BACKSPACE Backspace KEY_F0 T{ Function keys; space for 64 keys is reserved T} KEY_F(\fIn\fP) T{ Function key \fIn\fP where 0 \(<= \fIn\fP \(<= 63 T} KEY_DL Delete line KEY_IL Insert line KEY_DC Delete character KEY_IC Insert character/Enter insert mode KEY_EIC Exit insert character mode KEY_CLEAR Clear screen KEY_EOS Clear to end of screen KEY_EOL Clear to end of line KEY_SF Scroll one line forward KEY_SR Scroll one line backward (reverse) KEY_NPAGE Next page/Page up KEY_PPAGE Previous page/Page down KEY_STAB Set tab KEY_CTAB Clear tab KEY_CATAB Clear all tabs KEY_ENTER Enter/Send KEY_SRESET Soft (partial) reset KEY_RESET (Hard) reset KEY_PRINT Print/Copy KEY_LL Home down/Bottom (lower left) KEY_A1 Upper left of keypad KEY_A3 Upper right of keypad KEY_B2 Center of keypad KEY_C1 Lower left of keypad KEY_C3 Lower right of keypad KEY_BTAB Back tab key KEY_BEG Beg(inning) key KEY_CANCEL Cancel key KEY_CLOSE Close key KEY_COMMAND Cmd (command) key KEY_COPY Copy key KEY_CREATE Create key KEY_END End key KEY_EXIT Exit key KEY_FIND Find key KEY_HELP Help key KEY_MARK Mark key KEY_MESSAGE Message key KEY_MOUSE Mouse event occurred KEY_MOVE Move key KEY_NEXT Next object key KEY_OPEN Open key KEY_OPTIONS Options key KEY_PREVIOUS Previous object key KEY_REDO Redo key KEY_REFERENCE Ref(erence) key KEY_REFRESH Refresh key KEY_REPLACE Replace key KEY_RESIZE Screen resized KEY_RESTART Restart key KEY_RESUME Resume key KEY_SAVE Save key KEY_SELECT Select key KEY_SUSPEND Suspend key KEY_UNDO Undo key _ KEY_SBEG Shifted beginning key KEY_SCANCEL Shifted cancel key KEY_SCOMMAND Shifted command key KEY_SCOPY Shifted copy key KEY_SCREATE Shifted create key KEY_SDC Shifted delete character key KEY_SDL Shifted delete line key KEY_SEND Shifted end key KEY_SEOL Shifted clear line key KEY_SEXIT Shifted exit key KEY_SFIND Shifted find key KEY_SHELP Shifted help key KEY_SHOME Shifted home key KEY_SIC Shifted insert key KEY_SLEFT Shifted left arrow key KEY_SMESSAGE Shifted message key KEY_SMOVE Shifted move key KEY_SNEXT Shifted next object key KEY_SOPTIONS Shifted options key KEY_SPREVIOUS Shifted previous object key KEY_SPRINT Shifted print key KEY_SREDO Shifted redo key KEY_SREPLACE Shifted replace key KEY_SRIGHT Shifted right arrow key KEY_SRSUME Shifted resume key KEY_SSAVE Shifted save key KEY_SSUSPEND Shifted suspend key KEY_SUNDO Shifted undo key .TE .RE .PP Many keyboards feature a nine-key directional pad. .PP .RS .TS allbox center; C C C. A1 up A3 left B2 right C1 down C3 .TE .RE .sp Two of the symbols in the list above do .I not correspond to a physical key. .bP .B \%wgetch returns .BR \%KEY_RESIZE "," even if the window's keypad mode is disabled, if .I \%ncurses has handled a .I \%SIGWINCH signal since .B \%wgetch was called; see \fB\%initscr\fP(3X) and \fB\%resizeterm\fP(3X). .bP .B \%wgetch returns .B \%KEY_MOUSE to indicate that a mouse event is pending collection; see \fB\%curs_mouse\fP(3X). Receipt of this code requires a window's keypad mode to be enabled, because to interpret mouse input (as with \fI\%xterm\fP(1)'s mouse protocol), .I \%ncurses must read an escape sequence, as with a function key. .SS "Testing Key Codes" In .IR \%ncurses "," .B \%has_key returns a Boolean value indicating whether the terminal type recognizes its parameter as a key code value. See also \fB\%define_key\fP(3X) and \fB\%key_defined\fP(3X). .SH RETURN VALUE .B \%wgetch returns a key code identifying the key event as described above, which may include .B \%KEY_RESIZE or .B \%KEY_MOUSE indicating non-key events, or .B ERR on failure. .B \%wgetch fails if its timeout expires without any data arriving, which cannot happen if \fB\%nodelay\fP(3X) is in effect on the window. .PP In .IR \%ncurses , .B \%wgetch also fails if .bP the .I curses screen has not been initialized, .bP (for functions taking a .I \%WINDOW pointer argument) .I win is a null pointer, or .bP execution was interrupted by a signal, in which case the library sets .I \%errno to .IR \%EINTR "." .PP Functions prefixed with \*(``mv\*('' first perform cursor movement and fail if the position .RI ( y , .IR x ")" is outside the window boundaries. .PP .B \%ungetch returns .B OK on success and .B ERR on failure. In .IR \%ncurses , .B \%ungetch fails if .bP the .I curses screen has not been initialized, or .bP there is no more room in the input queue. .PP .B \%has_key returns .B TRUE or .BR FALSE "." .SH NOTES .BR \%getch "," .BR \%mvgetch "," and .B \%mvwgetch may be implemented as macros. .PP .I curses discourages assignment of the ESC key to a discrete function by the programmer because the library requires a delay while it awaits the potential remainder of a terminal escape sequence. .PP Some key strokes are indistinguishable from control characters; for example, .B \%KEY_ENTER may be the same as .BR \*^M "," .\" as with att630 or pccon+keys and .B \%KEY_BACKSPACE may be the same as .B \*^H .\" as with att505 or vt52-basic or .BR \*^? "." .\" as with pccon+keys or vt320 Consult the .I \%term\%info entry for the terminal type to determine whether this is the case; see \fB\%infocmp\fP(1). Some .I curses implementations, including .IR \%ncurses "," honor the .I \%term\%info key definitions; others treat such control characters specially. .PP .I curses distinguishes the Enter keys in the alphabetic and numeric keypad sections of a keyboard because (most) terminals do. .B \%KEY_ENTER refers to the key on the numeric keypad and, like other function keys, is reliably recognized only if the window's keypad mode is enabled. .bP The .I \%term\%info .B \%key_enter .RB ( kent ) capability describes the character (sequence) sent by the Enter key of a terminal's numeric (or similar) keypad. .bP \*(``Enter or send\*('' is X/Open Curses's description of this key. .PP .I curses treats the Enter or Return key in the .I alphabetic section of the keyboard differently. .bP It usually produces a control code for carriage return .RB ( \*^M ) or line feed .RB ( \*^J ). .bP Depending on the terminal mode (raw, cbreak, or canonical), and whether \fB\%nl\fP(3X) or \fB\%nonl\fP(3X) has been called, .B \%wgetch may return either a carriage return or line feed upon an Enter or Return key stroke. .PP Use of .B \%wgetch with \fB\%echo\fP(3X) and neither \fB\%cbreak\fP(3X) nor \fB\%raw\fP(3X) is not well-defined. .PP Historically, the list of key code macros above was influenced by the keyboard of the AT&T 7300 (also known variously as the \*(``3B1\*('', \*(``Safari 4\*('', and \*(``UNIX PC\*(''), a 1985 machine rich in function keys. Today's computer keyboards are based on that of the IBM PC/AT and tend to have fewer. A .I curses application can expect such a keyboard to transmit key codes .BR \%KEY_UP "," .BR \%KEY_DOWN "," .BR \%KEY_LEFT "," .BR \%KEY_RIGHT "," .BR \%KEY_HOME "," .BR \%KEY_END "," .B \%KEY_PPAGE (Page Up), .B \%KEY_NPAGE (Page Down), .B \%KEY_IC (Insert), .B \%KEY_DC (Delete), .BR \%KEY_A1 "," .BR \%KEY_A3 "," .BR \%KEY_B2 "," .BR \%KEY_C1 "," .BR \%KEY_C3 "," and .BI \%KEY_F( n ) for 1 \(<= .I n \(<= 12. .\" Other numeric keypad keys from the DEC VT220 (specifically, the .\" LK201 commonly used with it) and IBM PC/AT keyboards -- the comma .\" (DEC); plus, star, and slash (PC); and zero, dot, and minus (both) .\" have no standard key capability codes. .SH EXTENSIONS In .IR \%ncurses "," when a window's \*(``no time-out\*('' mode is .I not set, the .B \%ESCDELAY variable configures the duration of the timer used to disambiguate a function key character sequence from a series of key strokes beginning with ESC typed by the user; see \fB\%curs_variables\fP(3X). .PP .B \%has_key is an .I \%ncurses extension, and is not found in SVr4 .IR curses "," 4.4BSD .IR curses "," or any other previous .I curses implementation. .SH PORTABILITY Applications employing .I \%ncurses extensions should condition their use on the visibility of the .B \%NCURSES_VERSION preprocessor macro. .PP Except as noted in section \*(``EXTENSIONS\*('' above, X/Open Curses Issue\ 4 describes these functions. It specifies no error conditions for them. .PP SVr4 describes a successful return value only as \*(``an integer value other than .IR ERR \*(''. \" Courier roman in source; SVID 4, vol. 3, p. 494 .PP .I \%wgetch reads only single-byte characters. .PP The echo behavior of these functions on input of .I KEY_ or backspace characters is not documented in SVr4 .IR curses "." .PP The behavior of .I \%wgetch in the presence of signal handlers is not documented in SVr4 .I curses and is unspecified by X/Open Curses. In historical .I curses implementations, it varied depending on whether the operating system's dispatch of a signal to a handler interrupted a \fIread\fP(2) call in progress, and also (in some implementations) whether an input timeout or non-blocking mode had been set. A portable .I curses application prepares for two cases: (a) signal receipt does not interrupt .IR \%wgetch ";" and (b) signal receipt interrupts .I \%wgetch and causes it to return .I ERR with .I \%errno set to .IR \%EINTR "." .PP .I \%KEY_MOUSE is mentioned in X/Open Curses, along with a few related .I \%term\%info capabilities, but no higher-level functions use the feature. The implementation in .I \%ncurses is an extension. .PP .I \%KEY_RESIZE and .I \%has_key are extensions first implemented for .IR \%ncurses "." By 2022, .I \%PDCurses .\" https://web.archive.org/web/20220117232009/https://pdcurses.org/docs/MANUAL.html and NetBSD .I curses .\" https://web.archive.org/web/20200923185647/https://man.netbsd.org/curses_input.3 had added them along with .IR \%KEY_MOUSE "." .SH HISTORY 4BSD (1980) introduced .I \%wgetch and its variants. .PP SVr3 (1987) added .IR \%ungetch "." .PP .I \%ncurses 1.9.9g (1996) furnished the .I \%has_key extension. .SH SEE ALSO ECMA-6 \*(``7-bit coded Character Set\*('' \% .PP ECMA-48 \*(``Control Functions for Coded Character Sets\*('' \% .PP \fB\%curs_get_wch\fP(3X) describes comparable functions of the .I \%ncurses library in its wide-character configuration .RI \%( ncursesw ). .PP \fB\%curses\fP(3X), \fB\%curs_addch\fP(3X), \fB\%curs_inopts\fP(3X), \fB\%curs_mouse\fP(3X), \fB\%curs_move\fP(3X), \fB\%curs_outopts\fP(3X), \fB\%curs_refresh\fP(3X), \fB\%curs_variables\fP(3X), \fB\%resizeterm\fP(3X), \fB\%ascii\fP(7)