Neither "while $lock" nor "while ! $lock" are "atomic test and set" operations. You need to gate your critical (one-user-at-a-time) resource with some operation that both notices if a resource is available, and grabs that resource if so. Also, making such a request should block the process at the kernel level.

That's why flock is nice for that, if you have that. I have an example of that in my famous HIGHLANDER article.

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

In reply to •Re: Logical Conundrum by merlyn
in thread Logical Conundrum by mcogan1966

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