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Re: using fork

by moritz (Cardinal)
on Oct 14, 2013 at 16:27 UTC ( #1058197=note: print w/replies, xml ) Need Help??

in reply to using fork

What jethro said: Only fork if you need to do something in both processes.

If that's the case, here is a working example:

#!/usr/bin/env perl use 5.014; use strict; use warnings; my $pid = fork; if (!defined $pid) { die "Cannot fork: $!"; } elsif ($pid == 0) { # client process say "Client starting..."; sleep 10; # do something useful instead! say "Client terminating"; exit 0; } else { # parent process say "Parent process, waiting for child..."; # do something useful here! waitpid $pid, 0; } say "Parent process after child has finished";

One thing to note is that fork returns undef on failure, and undef == 0 compares as true, so your error handling wouldn't work. To easily test the error case, start a new bash and set ulimit -u $number_of_allowed_processes, then start the perl script.

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[Corion]: erix: I'm not sure if it really is MySQL - maybe MS SQL also has LIMIT 0
[erix]: it has TOP, IIRC
[Corion]: erix: Ah. I use where 1 = 0 for queries where I only am interested in the structure ;)
[erix]: 1=0 is as short as TOP :)
[erix]: "code of someone that died" -- kinda nice if your code stops working too
[erix]: hard to implement, hmm

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