If you're opening a file for destructive write, you have a bigger problem. Opening destroys the file, but you can't lock the file until you open it. One solution to this is to lock a different file, as someone else described. Another solution is to open the file twice: open it once for reading, lock it, and then open it for writing once you know you have the lock. As long as you keep the first filehandle open, you'll keep the lock.

You keep the lock on the now dead file, but you have a new file that exists but might not yet be fully written. And someone can come along and flock that! Now there are two flocks active. Repeat ad-nauseum, and you get an infinite number of flocks.

So, no, that's not the way to do it. Others have posted the proper way. Just wanted to point out that yours is flawed, so erase that part of your brain please. {grin}

-- Randal L. Schwartz, Perl hacker
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