Date: Tue, 04 Dec 2012 13:39:41 -0600 From: Martin McCormick <martin@dc.cis.okstate.edu> To: freebsd-questions@freebsd.org Subject: Safe Way to Tell if Process is Running Message-ID: <201212041939.qB4JdfGt085863@x.it.okstate.edu>
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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. Thank you. Martin McCormick WB5AGZ Stillwater, OK Systems Engineer OSU Information Technology Department Telecommunications Services Group
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