sys_time.h(3)              POSIX Programmer's Manual             sys_time.h(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       sys/time.h -- time types

SYNOPSIS
       #include <sys/time.h>

DESCRIPTION
       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 <sys/types.h>.

       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 argument of getitimer() and setitimer():

       ITIMER_REAL   Decrements in real time.

       ITIMER_VIRTUAL
                     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 [2]);

       Inclusion of the <sys/time.h> header may make visible all symbols from
       the <sys/select.h> header.

       The following sections are informative.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <sys_select.h>, <sys_types.h>

       The System Interfaces volume of POSIX.1-2017, futimens(), getitimer(),
       gettimeofday(), pselect()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy 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.opengroup.org/unix/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                  2017                        sys_time.h(3)
