Section: POSIX Programmer's Manual (0P)
Updated: 2003
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NAME

sys/time.h - time types  

SYNOPSIS

#include <sys/time.h>  

DESCRIPTION

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 [2]); (LEGACY )

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 IEEE Std 1003.1-2001, getitimer(), gettimeofday(), select(), setitimer()  

COPYRIGHT

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 .