NAME

gettimeofday − get the date and time

SYNOPSIS

#include <sys/time.h>

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

DESCRIPTION

The gettimeofday() function obtains the current time, expressed as seconds and microseconds since 00:00 Coordinated Universal Time (UTC), January  1, 1970, and stores it in the timeval structure pointed to by tp. The resolution of the system clock is unspecified.

If tzp is not a null pointer, the behaviour is unspecified. 

RETURN VALUE

The gettimeofday() function returns 0 and no value is reserved to indicate an error. 

ERRORS

No errors are defined. 

SEE ALSO

ctime(), ftime(), <sys/time.h>. 

CHANGE HISTORY

First released in Issue 4, Version 2. 

HP-UX EXTENSIONS

SYNOPSIS

#include <time.h>

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

DESCRIPTION

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 UTC */
    int  tz_dsttime;      /* type of DST correction to apply */
};

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

Security Restrictions

Only a user with appropriate privileges can set the time of day. 

RETURN VALUE

gettimeofday() return the following values:

 0 Successful completion. 

-1 Failure.  errno is set to indicate the error. 

ERRORS

gettimeofday() fails, errno is set to the following value. 

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

EXAMPLES

The following example calls gettimeofday() 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;

WARNINGS

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

AUTHOR

gettimeofday() was developed by the University of California, Berkeley, and SecureWare Inc. 

SEE ALSO

date(1), stime(2), time(2), ctime(3C). 

Hewlett-Packard Company  —  HP-UX Release 10.20:  July 1996