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copied!<p>If you end up using flock, here's some code to do it:</p> <pre><code>use Fcntl ':flock'; # Import LOCK_* constants # We will use this file path in error messages and function calls. # Don't type it out more than once in your code. Use a variable. my $file = '/path/to/some/file'; # Open the file for appending. Note the file path is quoted # in the error message. This helps debug situations where you # have a stray space at the start or end of the path. open(my $fh, '>>', $file) or die "Could not open '$file' - $!"; # Get exclusive lock (will block until it does) flock($fh, LOCK_EX) or die "Could not lock '$file' - $!"; # Do something with the file here... # Do NOT use flock() to unlock the file if you wrote to the # file in the "do something" section above. This could create # a race condition. The close() call below will unlock the # file for you, but only after writing any buffered data. # In a world of buffered i/o, some or all of your data may not # be written until close() completes. Always, always, ALWAYS # check the return value of close() if you wrote to the file! close($fh) or die "Could not write '$file' - $!"; </code></pre> <p>Some useful links:</p> <ul> <li><a href="http://www.perlmonks.org/?node_id=7058" rel="noreferrer">PerlMonks file locking tutorial</a> (somewhat old)</li> <li><a href="http://perldoc.perl.org/functions/flock.html" rel="noreferrer"><code>flock()</code> documentation</a></li> </ul> <p>In response to your added question, I'd say either place the lock on the file or create a file that you call 'lock' whenever the file is locked and delete it when it is no longer locked (and then make sure your programs obey those semantics).</p>

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