PROLOG

       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.

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 .