clock — Determine processor time
#include <time.h>
clock_t clock( |
void) ; |
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 32bit 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.
|