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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 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
       C89,  C99,  POSIX.1-2001.   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	 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.

       In  glibc 2.17 and earlier, clock() was implemented on top of times(2).
       For improved accuracy, since glibc 2.18,	it is implemented  on  top  of
       clock_gettime(2)	(using the CLOCK_PROCESS_CPUTIME_ID clock).

SEE ALSO
       clock_gettime(2), getrusage(2), times(2)

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       http://www.kernel.org/doc/man-pages/.

GNU				  2014-09-21			      CLOCK(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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