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

       clock(3,n) - Determine processor time(1,2,n)

       #include <time.h>

       clock_t clock(3,n)(void);

       The clock(3,n)() function returns an approximation of processor time(1,2,n) used by
       the program.

       The value returned is the CPU time(1,2,n) used so far as a clock_t; to get the
       number  of  seconds  used,  divide by CLOCKS_PER_SEC.  If the processor
       time(1,2,n) used is not available or its  value  cannot  be  represented,  the
       function returns the value (clock_t)-1.

       ANSI  C.  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(3,n)() at the start of the
       program to get maximum portability.

       Note  that  the  time(1,2,n)  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(3,n)()  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(1,8) the value returned by clock(3,n)().  The times()
       function, which explicitly returns  (separate)  information  about  the
       caller and its children, may be preferable.

       getrusage(2), times(2)

GNU                               2002-06-14                          CLOCK(3)

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