multiple instance on Unix

[Skip Montanaro]

    Nigel> I had a program that was called randomly by specific emails
    Nigel> arriving which asked for certain information. If two or more
    Nigel> emails arrived simultaneously then procmail asked two or more
    Nigel> instances of my program to run. These instances interfered with
    Nigel> one another, so I needed a process to stop that from
    Nigel> happening.

That process is procmail. <wink> Use procmail's lock mechanism and only one
instance of your program will run at a time.

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