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NAME
       clock - report CPU time used


SYNOPSIS
       #include <time.h>

       clock_t clock(void);


DESCRIPTION
       The  clock()  function shall return the implementation's best approximation to the processor time used by
       the process since the beginning of an implementation-defined era related only to the process invocation.


RETURN VALUE
       To determine the time in seconds, the value returned by clock() should be divided by  the  value  of  the
       macro  CLOCKS_PER_SEC.    CLOCKS_PER_SEC is defined to be one million in <time.h>.  If the processor time
       used is not available or its value  cannot  be  represented,  the  function  shall  return  the  value  (
       clock_t)-1.


ERRORS
       No errors are defined.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       In order to measure the time spent in a program, clock() should be called at the start of the program and
       its return value subtracted from the value returned by subsequent calls. The value returned by clock() is
       defined  for  compatibility across systems that have clocks with different resolutions. The resolution on
       any particular system need not be to microsecond accuracy.

       The value returned by clock() may wrap around on some implementations.  For example, on  a  machine  with
       32-bit values for clock_t, it wraps after 2147 seconds or 36 minutes.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       asctime() , ctime() , difftime() , gmtime() , localtime() , mktime() , strftime() , strptime() , time() ,
       utime() , the Base Definitions volume of IEEE Std 1003.1-2001, <time.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .