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>

COPYRIGHT

       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 .