sys_time.h(7POSIX) POSIX Programmer's Manual sys_time.h(7POSIX)
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of
this interface may differ (consult the corresponding Linux manual page for details of
Linux behavior), or the interface may not be implemented on Linux.
sys/time.h — time types
The <sys/time.h> header shall define the timeval structure, which shall include at least
the following members:
time_t tv_sec Seconds.
suseconds_t tv_usec Microseconds.
The <sys/time.h> header shall define the itimerval structure, which shall include at least
the following members:
struct timeval it_interval Timer interval.
struct timeval it_value Current value.
The <sys/time.h> header shall define the time_t and suseconds_t types as described in
The <sys/time.h> header shall define the fd_set type as described in <sys/select.h>.
The <sys/time.h> header shall define the following symbolic constants for the which argu‐
ment of getitimer() and setitimer():
ITIMER_REAL Decrements in real time.
Decrements in process virtual time.
ITIMER_PROF Decrements both in process virtual time and when the system is running on
behalf of the process.
The <sys/time.h> header shall define the following as described in <sys/select.h>:
FD_CLR() FD_ISSET() FD_SET() FD_ZERO() FD_SETSIZE
The following shall be declared as functions and may also be defined as macros. Function
prototypes shall be provided.
int getitimer(int, struct itimerval *);
int gettimeofday(struct timeval *restrict, void *restrict);
int setitimer(int, const struct itimerval *restrict,
struct itimerval *restrict);
int select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
struct timeval *restrict);
int utimes(const char *, const struct timeval );
Inclusion of the <sys/time.h> header may make visible all symbols from the <sys/select.h>
The following sections are informative.
The System Interfaces volume of POSIX.1‐2008, futimens(), getitimer(), gettimeofday(),
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrep‐
ancy between this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original Standard can be
obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely to have
been introduced during the conversion of the source files to man page format. To report
such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 sys_time.h(7POSIX)