PS command capturing CPU
 

I want to capture the cpu utilization of a process.
so I write a small script using this command

ps -o pid,pcpu <PID>

it does give me the cpu util for that pid however the number is different from TOP (irix on). the number from TOP is more accurate. since I have dual core cpu , how can I make the "ps" command works ?

thanks

don't use irix but try
to get a bigger range of pids

Noooo ...
The number from "top" is a different metric to that presented by "ps". Neither is necessarily more accurate than the other, given that /proc is the source of the data used by both.

Read the man pages, then decide what it really is you are trying to measure.

the program that I am tracking is a single threaded program. does that mean pcpu is more accurate ?
I do have quad dual core CPU (4 @dual core).

I read somewhere that pcpu is for the whole machine ie a CPU hog(100%) on a 4 CPU machine would register as 25%. Is this correct? So why then in my case , pcpu gives 75% and top irix on gives 25%?
What I want is a total CPU percentage.just like the description of pcpu I found on the net
Could you please help me understand ?

btw is there a command or switch to turn on irix mode in top if I want to use batch?

thanks