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CLOCK(3) Linux Programmer's Manual CLOCK(3)
clock - Determine processor time
#include <time.h>
clock_t clock(void);
The clock() function returns an approximation of processor time used by the
program.
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.
C89, C99, POSIX.1-2001. POSIX requires that CLOCKS_PER_SEC equals 1000000
independent of the actual resolution.
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 32-bit system where CLOCKS_PER_SEC
equals 1000000 this function will return the same value approximately every 72
minutes.
On several other implementations, the value returned by clock() also includes
the times of any children whose status has been collected via wait(2) (or
another wait-type call). Linux does not include the times of waited-for
children in the value returned by clock(). The times(2) function, which
explicitly returns (separate) information about the caller and its children,
may be preferable.
clock_gettime(2), getrusage(2), times(2)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2008-08-28 CLOCK(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface