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Identifying whether a process is running

by astroboy (Chaplain)
on Nov 09, 2009 at 22:30 UTC ( #806060=perlquestion: print w/ replies, xml ) Need Help??
astroboy has asked for the wisdom of the Perl Monks concerning the following question:

Comment on Identifying whether a process is running
Re: Identifying whether a process is running
by snoopy (Deacon) on Nov 09, 2009 at 23:15 UTC
    If you already know the process id(s), and own the processes, the kill builtin function might be of use.

    From the doco:

       kill SIGNAL, LIST
       .... 
            $cnt = kill 1, $child1, $child2
            kill 9, @goners;
    
        If SIGNAL is zero, no signal is sent to the process, but the
        kill(2) system call will check whether it's possible to send
        a signal to it (that means, to be brief, that the process is
        owned by the same user, or we are the super user).  This is
        a useful way to check that a child process is alive.
    
      Alas, this didn't work for me. I'm trying to see from a web page whether a daemon that should be running as root is actually there. The apache user can't issue a kill 0 to root's process (well it can, but it doesn't report the result correctly)
Re: Identifying whether a process is running
by BioLion (Curate) on Nov 10, 2009 at 11:57 UTC

    I recommended Parallel::Forker to someone else recently, and they had a similar problem ( how to kill deattached process ). Parallel::Forker has a poll method which should allow you to service any processes you have launched. Admittedly this doesn't work if you want to manipulate *any* process on the machine, but maybe it will help you...

    Just a something something...
      Thanks, but it's no what I'm after. I don't launch the process - I just want to see if it exists

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