clock(3) [redhat man page]

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

NAME

       clock - Determine processor time

SYNOPSIS

       #include <time.h>

       clock_t clock(void);

DESCRIPTION

       The clock() function returns an approximation of processor time used by the program.

RETURN VALUE

       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.

CONFORMING TO

       ANSI C.	POSIX requires that CLOCKS_PER_SEC equals 1000000 independent of the actual resolution.

NOTES

       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 32bit system where CLOCKS_PER_SEC equals 1000000 this function will return the same value approx-
       imately 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() (or another wait-type call).  Linux does not include the times of waited-for children in the value returned by clock().  The times()
       function, which explicitly returns (separate) information about the caller and its children, may be preferable.

SEE ALSO

       getrusage(2), times(2)

GNU
								    2002-06-14								  CLOCK(3)

clock(3C)						   Standard C Library Functions 						 clock(3C)

NAME

       clock - report CPU time used

SYNOPSIS

       #include <time.h>

       clock_t clock(void);

DESCRIPTION

       The clock() function returns the amount of CPU time (in microseconds) used since the first call to clock() in the calling process. The time
       reported is the sum of the user and system times of the calling process and its terminated child processes for which it	has  executed  the
       wait(3C) function, the pclose(3C) function, or the system(3C) function.

RETURN VALUES

       Dividing  the  value returned by clock() by the constant CLOCKS_PER_SEC, defined in the <time.h> header, will give the time in seconds.	If
       the process time used is not available or cannot be  represented, clock returns the value (clock_t) -1.

USAGE

       The value returned by clock() is defined in microseconds for compatibility with systems that have CPU clocks with much  higher  resolution.
       Because of this, the value returned will wrap around after accumulating only 2147 seconds of CPU time (about 36 minutes).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       times(2), popen(3C), system(3C), wait(3C), attributes(5), standards(5)

SunOS 5.11							    24 Jul 2002 							 clock(3C)