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Name

gettimeofday, settimeofday - get or set the date and time

Synopsis

#include <sys/time.h>

int gettimeofday(struct timeval *tp, void * );

int settimeofday(struct timeval *tp, void * );

MT-Level

MT-Safe

Description

gettimeofday() gets and settimeofday() sets the system’s notion of the current time. The current time is expressed in elapsed seconds and microseconds since 00:00 Universal Coordinated Time, January 1, 1970. The resolution of the system clock is hardware dependent; the time may be updated continuously or in clock ticks.

tp points to a timeval structure, which includes the following members: 


long    tv_sec;    /* seconds since Jan. 1, 1970 */
long    tv_usec;   /* and microseconds */

If tp is a null pointer, the current time information is not returned or set.

The TZ environment variable holds time zone information. See TIMEZONE(4) .

The second argument to gettimeofday() and settimeofday() should be a pointer to NULL.

Only the privileged user may set the time of day.

See Also

adjtime(2) , ctime(3C) , TIMEZONE(4)

Return Values

A -1 return value indicates that an error occurred and errno has been set.

Errors

The following error codes may be set in errno:
EINVAL
tp specifies an invalid time.
EPERM
A user other than the privileged user attempted to set the time or time zone.

Notes

The implementation of settimeofday() ignores the tv_usec field of tp. If the time needs to be set with better than one second accuracy, call settimeofday() for the seconds and then adjtime() for finer accuracy.

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