In fact it is not guaranteed. We reinvented our log wheel and 95% of log activity is on the same log file, and we find it very useful.

From perl docs, various web examples, this merlyn's webcolumn (written when I didn't even know what perl was) and extensive™ testing, I learnt that using flock() with LOCK_EX flag is the only way to have consistent updates/writes by many processes onto a single log file (or page-counters, for that matter), though this method is not reliable across platforms.

Not using flock resulted in mangled log files, with different processes log buffers being mixed and truncated at random.

In reply to Re^2: Multiple processes, one log file? by cosimo
in thread Multiple processes, one log file? by splinky

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