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:
suseconds_t tv_usec Microseconds.
The <sys/time.h> header shall define the itimerval structure, which shall include at least the following members:
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():
Decrements in real time.
Decrements in process virtual time.
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.
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> header.
The following sections are informative.
The System Interfaces volume of POSIX.1-2017, futimens(), getitimer(), gettimeofday(), pselect()
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 .