man Pages(3): Library Routines

gettimeofday(3C)

NAME

gettimeofday, settimeofday- get or set the date and time

SYNOPSIS

#include <sys/time.h>

tp

DESCRIPTION

The gettimeofday() function gets and the settimeofday() function 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.

The tp argument 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 super-user may set the time of day.

RETURN VALUES

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

The gettimeofday() function will fail if:

EINVAL: The structure pointed to by tp specifies an invalid time.
EPERM: A user other than the privileged user attempted to set the time or time zone.

Additionally, the gettimeofday() function will fail for 32-bit interfaces if:

EOVERFLOW: The system time has progressed beyond 2038, thus the size of the tv_sec member of the timeval structure pointed to by tp is insufficient to hold the current time in seconds.

USAGE

If the tv_usec member of tp is > 500000, settimeofday() rounds the seconds upward. If the time needs to be set with better than one second accuracy, call settimeofday() for the seconds and then adjtime(2) for finer accuracy.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
MT-Level	MT-Safe