FAQ 5.23 I still don't get locking. I just want to increment the number in the file. How can I do th


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5.23: 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 my $fh, "numfile", O_RDWR|O_CREAT or die "can't open numfile: $!";
flock $fh, LOCK_EX or die "can't flock numfile: $!";
my $num = <$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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