clock man page on Archlinux

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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.

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

       clock_gettime(2), getrusage(2), times(2)

       This  page  is  part of release 3.65 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at

GNU				  2013-08-19			      CLOCK(3)

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