From: George Mochrie <geo@...>
Date: 2004-08-26T09:10:59+09:00
Subject: Re: easy way to check if a pid is running?

the perfect solution... thanks :)

On Wednesday 25 August 2004 22:26, Mark Hubbart wrote:
> On Aug 25, 2004, at 2:01 PM, Gennady wrote:
> > George Mochrie wrote:
> >> hi
> >> A quick question:
> >> Is there an easy way to check if a process is running given it's PID?
> >> There seems to be nothing like Process.exists?(pid). If I was root I
> >> could use Process.kill(0,pid) to test, but the program needs to run
> >> as a plain user. Do
> >
> > Not only root can do kill(0, pid), any user can send signal (or 0) to
> > his/her own processes.
> >
> > On systems that have /proc you can also check for presence of a
> > directory named like pid there.
>
> You can't send a signal, but you get a different error:
>
> mark@eMac% irb --prompt xmp
>
> Process.kill 0, 1
> Errno::EPERM: Operation not permitted
>          from (irb):2:in `kill'
>          from (irb):2
>
> Process.kill 0, 512
> Errno::ESRCH: No such process
>          from (irb):3:in `kill'
>          from (irb):3
>
> Process.kill 0, 419
>      ==>1
>
> process 1 is owned by root, 512 doesn't exist, 419 was mine.
>
> So, Process.exists? could be:
>
> def Process.exists?(pid)
>    Process.kill 0, pid
>    return true
> rescue Errno::ESRCH
>    return false
> rescue Exception
>    return true
> end
>      ==>nil
>
> Process.exists? 1
>      ==>true
>
> Process.exists? 512
>      ==>false
>
> Process.exists? 419
>      ==>true
>
> >> I have to parse the output from ps -e?
> >> Thanks in advance :)
> >
> > Gennady.

-- 
George Mochrie
aka Drasil
ICQ# 84423409