FAQ 5.20 I still don't get locking. I just want to increment the number in the file. How...

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5.20: I still don't get locking.  I just want to increment the number in the
file.  How can I do this?

    Didn't anyone ever tell you web-page hit counters were useless? They
    don't count number of hits, they're a waste of time, and they serve only
    to stroke the writer's vanity. It's better to pick a random number;
    they're more realistic.

    Anyway, this is what you can do if you can't help yourself.

        use Fcntl qw(:DEFAULT :flock);
        sysopen(FH, "numfile", O_RDWR|O_CREAT)       or die "can't open numfile:
        flock(FH, LOCK_EX)                           or die "can't flock
numfile: $!";
        $num = <FH> || 0;
        seek(FH, 0, 0)                               or die "can't rewind
numfile: $!";
        truncate(FH, 0)                              or die "can't truncate
numfile: $!";
        (print FH $num+1, "\n")                      or die "can't write
numfile: $!";
        close FH                                     or die "can't close
numfile: $!";

    Here's a much better web-page hit counter:

        $hits = int( (time() - 850_000_000) / rand(1_000) );

    If the count doesn't impress your friends, then the code might. :-)


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