clock - phpMan

CLOCK(3)                   Linux Programmer’s Manual                  CLOCK(3)



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 pro-
       gram.

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 avail-
       able  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 maxi-
       mum 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() (or another  wait-
       type  call).   Linux does not include the times of waited-for children in the value
       returned by clock().  The times() function,  which  explicitly  returns  (separate)
       information about the caller and its children, may be preferable.

SEE ALSO
       getrusage(2), times(2)



GNU                               2002-06-14                          CLOCK(3)

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