CLOCK

Section: Linux Programmer's Manual (3 )
Updated: 1993-04-21
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NAME

clock - Determine processor time

SYNOPSIS

#include <time.h>

clock_t clock(void);

DESCRIPTION

The clock() function returns an approximation of processor time used by the program.

RETURN VALUE

The value returned is the CPU time used so far as a clock_t; to get the number of seconds used, divide by CLOCKS_PER_SEC. If the processor time used is not available or its value cannot be represented, the function returns the value (clock_t)-1.

CONFORMING TO

ANSI C. POSIX requires that CLOCKS_PER_SEC equals 1000000 independent of the actual resolution.

NOTES

The C standard allows for arbitrary values at the start of the program; subtract the value returned from a call to clock() at the start of the program to get maximum portability.

Note that the time can wrap around. On a 32bit system where CLOCKS_PER_SEC equals 1000000 this function will return the same value approximately every 72 minutes.

The times() function call returns more information.

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