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.
STANDARDS CONFORMANCE
clock(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, ANSI C
