Time command issuing all zeroes (is now considered homework help) Post: 302834385

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Homework and Emergencies Homework & Coursework Questions Time command issuing all zeroes (is now considered homework help) Post 302834385 by Don Cragun on Thursday 18th of July 2013 08:50:59 PM

07-18-2013

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The number following "real" is the time that elapsed from when the command started running until it finished (this is sometimes referred to as wall clock time); the number following "user" is the time that was attributed to your user code while the command was running; and the number following "sys" is the time that was attributed to OS (kernel) code while the command was running. On a multi-processor system, user time + sys time could be larger than real time if multiple cores were running different parts of your code at the same time. Real time could easily be much more than the sum of user time + sys time if your code was waiting for I/O or was delayed while other code was being run on your system by other processes.

PS Note that when the shell you're using prints time output in the format:

Code:

3.36u 0.07s 0:05.43 63.2%

the 1st number (ending with 'u') is user time, the 2nd number (ending with 's') is sys time, and the 3rd part is wall clock time. The percentage at the end is how much of the system the command was using during the life of the command: ((user + sys) / real) * 100.

Last edited by Don Cragun; 07-18-2013 at 09:58 PM.. Reason: Add PS comparing different time output formats.

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LEARN ABOUT HPUX

clock

clock(3C)																 clock(3C)

NAME

       clock() - report CPU time used

SYNOPSIS

DESCRIPTION

       returns	the amount of CPU time (in microseconds) used since the first call to 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 , or (see wait(2) , system(3S), and popen(3S)).  To deter-
       mine the time in seconds, the value returned by should be divided by the value of the macro

       The resolution of the clock varies, depending on the hardware and on software configuration.

       If the processor time used is not available or its value cannot be represented, the function returns the value

WARNINGS

       The  value returned by is defined in microseconds for compatibility with systems that have CPU clocks with much higher resolution.  Because
       of this, the value returned wraps around after accumulating only 4295 seconds of CPU time (about 72 minutes).

DEPENDENCIES

       The default clock resolution is 10 milliseconds.

SEE ALSO

       times(2), wait(2), system(3S), thread_safety(5).

STANDARDS CONFORMANCE

																	 clock(3C)

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