First of all I would suggest moving the information on where those directories are into a configuration file. You will (presumably) have a number of CGI scripts and you don't want to have the same information included in every one of them. (Alternately you could have a makefile for your scripts that inserts that information in each of them.)

Secondly your flock makes all of the usual mistakes. When you close it you have no guarantee that when you turn around you will be next to get the file. What is likely to happen sooner or later is that you read, someone else is waiting to read, you close, it gets the lock and reads, closes, you write, it writes. Thereby missing a count. What is worse is if you manage to open for write (wiping out the file) before it reads.

If you must flock the file you are writing, the right way to do it is a non-destructive open for append or read, flock for writing, seek to the beginning, read, seek back, truncate, write, close (without unlocking). The simpler (but still safe) way is to have a sentinel (eg "counter.lock") that you open, flock, access the other file, then close. (Don't ever delete this!)

For a rather heavy version of the sentinel file approach see Simple Locking.

In reply to Re (tilly) 1: Flock Feedback by tilly
in thread Flock Feedback by footpad

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