Date: Tue, 4 Dec 2012 21:08:37 +0000 From: Steve O'Hara-Smith <ateve@sohara.org> To: freebsd-questions@freebsd.org Subject: Re: Safe Way to Tell if Process is Running Message-ID: <20121204210837.1eaa847ea1eaec7850ba8054@sohara.org> In-Reply-To: <201212042050.qB4Koc70086364@x.it.okstate.edu> References: <201212042050.qB4Koc70086364@x.it.okstate.edu>
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On Tue, 04 Dec 2012 14:50:38 -0600
Martin McCormick <martin@x.it.okstate.edu> wrote:
> Robert Bonomi writes:
> > 'man 2 kill' tells all.
>
> I believe that is the first or second time I have used
> Section 2. I appreciate the reminder. It looks like ps -p ###
> >/dev/null appears to do what I need without producing output
>
> ps -p 54321 >/dev/null && date ran the date command if there was
> a process with that number and produced nothing if no process
> 54321 existed.
That's not a certain test, ps can miss processes. Given that you
are working in C you would be better off calling kill directly rather than
spawning a process with system and risking picking up some odd
implementation of a command.
if (-1 != kill(pid, 0)) {
// Process exists
} else if (EPERM == errno) {
// No permission to signal process - belongs to someone else
} else if (ESRCH == errno) {
// Process does not exist
} else {
// Something weird and undocumented went wrong
}
--
Steve O'Hara-Smith <ateve@sohara.org>
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