multiple instance on Unix

Ville Vainio ville at
Thu Sep 30 11:07:32 CEST 2004

>>>>> "Andrew" == Andrew Dalke <adalke at> writes:

    Andrew> Ville Vainio wrote:
    >> I'd go for pid file - in Unix at least, process id's are not reused so
    >> if no process for the pid in pidfile exists, the process has died.

    Andrew> They aren't?  I remember seeing them cycle before.
    Andrew> Granted, pids are now, what 32 bit numbers so it's rare,
    Andrew> but there's nothing in the Unix specs to say they cannot.

Ok, I stand corrected. My Linux experiments indicated that they didn't
cycle in a "disruptive" fashion like NT seemed to do (where pid
collision is extremely likely).

Luckily, I implemented the pid check by checking the process name as
well :-).

Ville Vainio

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