Eeek! No! That code snippet is incomplete, and will eventually get people into trouble if they're trying to run on multiple platforms.

If you intent to append to a file, you need to handle the small, but very real timing window between opening the file and acquiring the lock. Within that window, a different process can write the the file, leaving you with a bogus seek pointer. Best case, you'll lose the last record(s) written. Worse case, you'll write into the midst of them, leaving corrupted records.

To mitigate the timing window, add the following line 

    use Fcntl ':flock';
    ...
    open FH, ">>$file" or die "Can't open $file: $!";
    flock FH, LOCK_EX; # lock it
+++ seek FH, 0, 2; # in case eof moved

    # ... print() to file here

    flock FH, LOCK_UN;
    close FH;

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In reply to Re: Re: (OT?) File Locking by dws
in thread (OT?) File Locking by Anonymous Monk

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