help using the wait() command

Ras has asked for the wisdom of the Perl Monks concerning the following question:

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Re: help using the wait() command by VSarkiss (Monsignor) on Feb 01, 2002 at 23:27 UTC
Actually, `wait` will return when one of the child processes exits, but it will "wait" (in some sense) on all of them. In other words, if you call `wait` and you have child processes that are executing, it will block. It will return when any one of them (or several if they happen to exit simultaneously) exits. If you fork off multiple children, and you want to block until all of them exit, just put `wait` in a loop: `1 while wait() > 0;` More information at perlfunc:wait and wait. HTH	[reply] [d/l] [select]
Re: help using the wait() command by Zaxo (Archbishop) on Feb 02, 2002 at 01:52 UTC
wait will sit and sleep until SIGCHLD triggers from any source. If you want to wait for a specific child, use waitpid. My pet idiom for waiting for multiple kids is this: `my %family_bible = (); # @todo is an array of coderefs sub () {...;return $status} for (@todo) { my $kid; defined $kid = fork or last; $kid or exit &$_; $family_bible{$kid}++; } delete $family_bible{-wait} while %family_bible;` [download] If the kids need arguments, or you need to check their exit status, you'll need to modify the control structures. The family_bible hash makes the wait strategy insensitive to ordering (as it must be) and provides a convenient control structure for knowing when you're done. There are, of course, CPAN modules to handle all this for you. Parallel::ForkManager is one I recommend. After Compline, Zaxo	[reply] [d/l]