NAME

sys/time.h - time types

SYNOPSIS

^[XSI] #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. 

^[OB] 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>.

^[OB] 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.

[OB]
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.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

<sys/select.h> , <sys/types.h>

XSH futimens , getitimer , gettimeofday , pselect

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

The type of tv_usec is changed from long to suseconds_t.

Issue 6

The restrict keyword is added to the prototypes for gettimeofday(), select(), and setitimer().

The note is added that inclusion of this header may also make symbols visible from <sys/select.h>.

The utimes() function is marked LEGACY.

Issue 7

This reference page is clarified with respect to macros and symbolic constants.