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sys/time.h - time types
The <sys/time.h> header shall define the timeval structure that includes 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 that includes at least the following members: struct timeval it_interval Timer interval. struct timeval it_value Current value. The time_t and suseconds_t types shall be defined as described in <sys/types.h> . The fd_set type shall be defined as described in <sys/select.h> . The <sys/time.h> header shall define the following values 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 following shall be defined 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 select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict, struct timeval *restrict); int setitimer(int, const struct itimerval *restrict, struct itimerval *restrict); int utimes(const char *, const struct timeval ); (LEGACY ) 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 IEEE Std 1003.1-2001, getitimer(), gettimeofday(), select(), setitimer()
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .