Date: Tue, 4 Dec 2012 14:09:37 -0600 (CST) From: Robert Bonomi <bonomi@mail.r-bonomi.com> To: martin@dc.cis.okstate.edu Cc: freebsd-questions@freebsd.org Subject: Re: Safe Way to Tell if Process is Running Message-ID: <201212042009.qB4K9b60009439@mail.r-bonomi.com> In-Reply-To: <201212041939.qB4JdfGt085863@x.it.okstate.edu>
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> Subject: Safe Way to Tell if Process is Running > Date: Tue, 04 Dec 2012 13:39:41 -0600 > From: Martin McCormick <martin@dc.cis.okstate.edu> > > About 20 years ago, I saw some code in which you > verified whether or not a process was running by giving it a > kill -0 command. If the process was running, nothing happened to > it but your kill -0 command exited with a 0 status. If there was > no process with that PID, the kill command exited non-zero. > > I use this in a system(command); in a C program I wrote > some years ago and I think this is now causing a segmentation > fault when the process number being signalled doesn't exist. Is > there a better way to determine if process number 12345 is > running without bothering it? > > None of the documentation on kill (1) shows a signal 0 > nor does kill -l. > > Something tells me this is a bad idea these days, but I > still need an easy way to see if XYZ process is still alive. 'man 2 kill' tells all.
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