CLOCK(3C) Standard C Library Functions CLOCK(3C)

NAME

clock - report CPU time used

SYNOPSIS

#include <time.h>

clock_t clock(void);

DESCRIPTION

The clock() function returns the amount of CPU time (in microseconds)
used since the first call to clock() in the calling process. 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 the wait(3C)
function, the pclose(3C) function, or the system(3C) function.

RETURN VALUES

Dividing the value returned by clock() by the constant CLOCKS_PER_SEC,
defined in the <time.h> header, will give the time in seconds. If the
process time used is not available or cannot be represented, clock
returns the value (clock_t) -1.

USAGE

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 will wrap around after
accumulating only 2147 seconds of CPU time (about 36 minutes).

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO

times(2), popen(3C), system(3C), wait(3C), attributes(7), standards(7)


July 24, 2002 CLOCK(3C)