CLOCK(P)							     CLOCK(P)



NAME
       clock - report CPU time used

SYNOPSIS
       #include 

       clock_t clock(void);


DESCRIPTION
       The clock() function shall return the implementation's best approxima-
       tion 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 .  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 vol-
       ume of IEEE Std 1003.1-2001, 

COPYRIGHT
       Portions	 of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information  Technol-
       ogy  --	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 .



POSIX				     2003			     CLOCK(P)

UNIX/Linux commands referenced on this page:

1. time
2. spent
3. at