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POSIX Manual Pages


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


#include <sys/time.h>


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.








<sys_select.h>, <sys_types.h>
The System Interfaces volume of POSIX.1-2008, futimens(), getitimer(), gettimeofday(), pselect()


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 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 .
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 .
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