Identifying whether a process is running

astroboy has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Identifying whether a process is running by snoopy (Curate) 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.	[reply]
Re^2: Identifying whether a process is running by astroboy (Chaplain) on Nov 10, 2009 at 20:51 UTC
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)	[reply]
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...	[reply] [d/l] [select]
Re^2: Identifying whether a process is running by astroboy (Chaplain) on Nov 10, 2009 at 20:53 UTC
Thanks, but it's no what I'm after. I don't launch the process - I just want to see if it exists	[reply]