UNIX for Dummies Questions & Answers

Hi,

I will be creating a process myself and I want to know the average CPU and RAM used by the process over the lifetime of the process. I see that there are various tools available(pidstat) for doing , I was wondering if it possible to do it in a single command while creation.
Thanks in advance.

Regards,
koustubh

No, this isn't possible, save for some very limited (and probably pointless) exceptions: how much RAM and how many processor cycles your process consumes depends on things only known during runtime: user actions, size and content of input files, signals issued to the process, etc.. All these things will influence the actions of and hence the resources consumed by a process.

It is possible to determines such resources consumed afore in some very specialised areas: real-time signal processors for instance. But it is possible only because the input is of a known size (like: "20-bit sampling at 96kHz", as in AC'97, which yields a constant data rate of about 512 kB/s) and content and there are no other outside factors (signals, user interaction, ...) to influence the operation of such a program.

I hope this helps.

bakunin

I understand what you are saying. But I want the amount of memory used by a process over its lifetime. I have the time for which the process runs, and using the values for the amount of memory used I can judge its performace.

OK, i have misunderstood your intention. In this case have a look at the man page of ps, especially the -o vsz option, which displays the memory held by a process. Select some sampling interval and issue this command repeatedly, save the output to a file and calculate the average from there. Here is a sketch of such a script:

Code:

#!/bin/sh

typeset -i iPID=<process-ID of the process in question>
typeset -i iRate=<sampling interval in seconds>
typeset    fOut="/path/to/outputfile"

rm -f "$fOut" ; touch "$fOut"

while ps -p "$iPID" >/dev/null 2>&1 ; do
     ps -p "$iPID" -o vsz <and what other info you are interested in> >> "$fOut"
     sleep $iRate
done

exit 0

Depending on your system output of ps might vary so you might have to "massage" the captured output of ps somewhat for calculation.

I hope this helps.

bakunin