HP-UX Reference (11i v1 00/12) - 3 Library Functions A-M (vol 6)
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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
/build/1111/BRICK/man3/!!!intro.3c
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c
clock(3C) clock(3C)
NAME
clock() - report CPU time used
SYNOPSIS
#include <time.h>
clock_t clock(void);
DESCRIPTION
clock() returns the amount of CPU time (in microseconds) used since the first call to clock(). The
time reported is the sum of the user and system times of the calling process and its terminated child
processes for which it has executed wait() , system() or pclose() (see wait(2) , system(3S), and
popen(3S)). To determine the time in seconds, the value returned by clock() should be divided by the
value of the macro CLOCKS_PER_SEC.
The resolution of the clock varies, depending on the hardware and on software configuration.
If the processor time used is not available or its value cannot be represented, the function returns the value
(clock_t)−1.
APPLICATION USAGE
clock() is thread-safe. It is not async-cancel-safe.
WARNINGS
The value returned by clock() is defined in microseconds for compatibility with systems that have
CPU
clocks with much higher resolution. Because of this, the value returned wraps around after accumulating
only 4295 seconds of CPU time (about 72 minutes).
DEPENDENCIES
The default clock resolution is 10 milliseconds.
SEE ALSO
times(2), wait(2), system(3S).
STANDARDS CONFORMANCE
clock(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, ANSI C
HP-UX Release 11i: December 2000 − 1 − Section 3−−73
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