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 application is not a UNIX-conforming application.
See the
HP-UX EXTENSIONS
section for treatment of a non-null pointer for the
tzp
argument.
RETURN VALUE
The
gettimeofday()
function returns 0 and no value is reserved to indicate an error.
See the
HP-UX EXTENSIONS
section for function return values under HP-UX.
ERRORS
No errors are defined.
See the
HP-UX EXTENSIONS
section for error values under HP-UX.
CHANGE HISTORY
First released in Issue 4, Version 2.
gettimeofday HP-UX EXTENSIONS
SYNOPSIS (HP-UX)
#include <sys/time.h>
int gettimeofday(struct timeval *tp,
struct timezone *tzp);
DESCRIPTION
When
gettimeofday()
is called under HP-UX,
extensions apply to the time zone parameter,
the return value, and errors.
If the
tzp
parameter is not a null pointer, it is interpreted as a pointer to a
struct timezone
under HP-UX.
The
struct timezone
has the following fields:
- tz_minuteswest
The number of minutes that the local time zone is west of UTC.
- tz_dsttime
A flag that, if nonzero, indicates that Daylight Savings Time
(DST) 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 under HP-UX:
- 0
Successful completion.
- -1
Failure.
errno
is set to indicate the error.
ERRORS
If
gettimeofday()
fails,
errno
is set to the following value under HP-UX:
- [EFAULT]
An argument address referenced invalid memory.
The reliable detection of this error is implementation dependent.
EXAMPLES
The following HP-UX 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 HP.
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