GETTIMEOFDAY(2) — HP-UX

NAME

gettimeofday, settimeofday − get/set date and time

SYNOPSIS

#include <time.h>

int gettimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;

int settimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;

DESCRIPTION

Gettimeofday returns and settimeofday sets the system’s notion of the current Greenwich time and the system’s notion of the current time zone. Time is expressed in seconds and microseconds since midnight January 1, 1970.

The structures pointed to by tp and tzp are defined in <time.h> as:

struct timeval {

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

};
struct timezone {

	int	tz_minuteswest;	/* of Greenwich */
	int	tz_dsttime;	/* type of dst correction to apply */

};

The timezone structure indicates the local time zone (measured in minutes of time westward from Greenwich), and a flag that, if nonzero, indicates that Daylight Saving time applies locally during the appropriate part of the year. Programs should use this timezone information only in the absence of the TZ environment variable.

Only the super-user may set the time of day.

EXAMPLES

The following example calls gettimeofday(2) twice. It then computes the lapsed time between the calls in seconds and microseconds and stores the result in a timeval structure:

struct timeval	first,
	second,
	lapsed;

struct timezone tzp;

gettimeofday (&first, &tzp); /* lapsed time */ gettimeofday (&second, &tzp); if (first.tv_usec > second.tv_usec) {

second.tv_usec += 1000000;
second.tv_sec--;

}
lapsed.tv_usec = second.tv_usec - first.tv_usec;
lapsed.tv_sec = second.tv_sec - first.tv_sec;

RETURN VALUE

A 0 return value indicates that the call succeeded. A −1 return value indicates an error occurred, and in this case an error code is stored into the global variable errno.

ERRORS

The following error codes may be set in errno:

[EFAULT] An argument address referenced invalid memory. The reliable detection of this error will be implementation dependent.

[EPERM] A user other than the super-user attempted to set the time.

WARNINGS

The microsecond value usually has a granularity much greater than one due to the resolution of the system clock. Depending on any granularity (particularly of one) will render code non-portable.

DEPENDENCIES

Series 300
Gettimeofday has a granularity of 4 microseconds.

Series 500
Gettimeofday has a granularity of 10 milliseconds.

Series 300 Diskless
On systems that are members of a cluster, setting the time of day will set the date and timezone on all systems in the cluster.

AUTHOR

Gettimeofday was developed by the University of California, Berkeley.

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