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Forum => newLISP in the real world => Topic started by: kanen on February 23, 2011, 11:49:00 AM

Title: Simple pid file check
Post by: kanen on February 23, 2011, 11:49:00 AM
Hello all,



I am interested in testing for a running process and, if it is not running, restarting it.



Right now, I'm writing /tmp/app.pid files for everything I run. If I need to stop a running app, I call:


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(destroy-pid (int (read-file "/tmp/app.pid")))

Which works, of course.



But, I want to test to see if the pid is actually running. Is there a clean, easy way to do this (something I am missing in unix.lsp, for example?)



Thanks.
Title: Re: Simple pid file check
Post by: cormullion on February 23, 2011, 02:39:26 PM
Send 0 to a process using 'kill' - it will return true if the process is running (and accepting signals), nil if it isn't. So, after loading unix.lsp:


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(kill pid 0)


will return true if PID is running. That's assuming you know the process ID .. :) If you don't know the PID, then you could use ps -ef | grep "name" to get it...
Title: Re: Simple pid file check
Post by: kanen on February 25, 2011, 07:18:25 PM
So simple!



Thanks. That's exactly what I was missing. No idea why it didn't occur to me.



Perfect. Thanks!


Quote from: "cormullion"Send 0 to a process using 'kill' - it will return true if the process is running (and accepting signals), nil if it isn't. So, after loading unix.lsp:


Code Select
(kill pid 0)


will return true if PID is running. That's assuming you know the process ID .. :) If you don't know the PID, then you could use ps -ef | grep "name" to get it...
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