.\" Copyright, the authors of the Linux man-pages project
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.TH time_t 3type 2025-10-29 "Linux man-pages 6.16"
.SH NAME
time_t, suseconds_t, useconds_t \- integer time
.SH LIBRARY
Standard C library
.RI ( libc )
.SH SYNOPSIS
.nf
.B #include <time.h>
.P
.BR typedef " /* ... */  " time_t;
.P
.B #include <sys/types.h>
.P
.BR typedef " /* ... */  " suseconds_t;
.BR typedef " /* ... */  " useconds_t;
.fi
.SH DESCRIPTION
.TP
.I time_t
Used for time in seconds.
According to POSIX,
it is an integer type
of at least 64 bits.
.TP
.I suseconds_t
Used for time in microseconds.
It is a signed integer type
capable of storing values at least in the range
.RB [ \-1 ,
.BR 1000000 ].
.TP
.I useconds_t
Used for time in microseconds.
It is an unsigned integer type
capable of storing values at least in the range
.RB [ 0 ,
.BR 1000000 ].
.SH STANDARDS
.TP
.I time_t
C11, POSIX.1-2024.
.TP
.I suseconds_t
POSIX.1-2024.
.TP
.I useconds_t
None.
.SH HISTORY
.TP
.I time_t
C89, POSIX.1-2001.
.TP
.I suseconds_t
POSIX.1-2001.
.TP
.I useconds_t
POSIX.1-2001.
Removed in POSIX.1-2008.
.SS Header files
.I <sched.h>
defines
.I time_t
since POSIX.1-2008.
.SS time_t
In POSIX.1-2001,
.I time_t
was specified as being either an integer type or a real-floating type.
However,
existing implementations used an integer type,
and POSIX.1-2008 tightened the specification to reflect this.
.P
POSIX.1-2024 required that the width of
.I time_t
is at least 64 bits.
.SH NOTES
On some architectures,
the width of
.I time_t
can be controlled with the feature test macro
.BR _TIME_BITS .
See
.BR feature_test_macros (7).
.P
The following headers also provide
.IR time_t :
.IR <sched.h> ,
.IR <sys/msg.h> ,
.IR <sys/select.h> ,
.IR <sys/sem.h> ,
.IR <sys/shm.h> ,
.IR <sys/stat.h> ,
.IR <sys/time.h> ,
.IR <sys/types.h> ,
and
.IR <utime.h> .
.P
The following headers also provide
.IR suseconds_t :
.I <sys/select.h>
and
.IR <sys/time.h> .
.P
The following headers also provided
.IR useconds_t :
.IR <unistd.h> .
.SH SEE ALSO
.BR stime (2),
.BR time (2),
.BR ctime (3),
.BR difftime (3),
.BR usleep (3),
.BR timeval (3type)