I would like to have a parent process spawn a child to perform some task every 5 seconds. I would also like to perform some cleanup every time a child exits.

Unfortunately it appears that sleep exits prematurely when a CHLD signal handler is triggered; for example, 

#!/usr/bin/perl

use strict;
$|++;
my $pid = fork();
if ($pid) {
        # the parent does not exit prematurely when the handler
        # is set to IGNORE
        $SIG{CHLD} = sub { print "$$: Reaping a child process in child
+ signal handler ...\n" };
        print "$$: Parent sleeping 5 seconds at [".localtime()."] ...\
+n";
        sleep 5;
        print "$$: That was refreshing.  The time is now [".localtime(
+)."].\n";
        exit(0);
} else {
        print "$$: \tChild sleeping for 2 seconds ...\n";
        sleep 2;
        print "$$: \tChild exiting at [".localtime()."] ...\n";
        exit(0);
}

[download]
results in 
3978:   Child sleeping for 2 seconds ...
3977: Parent sleeping 5 seconds at [Tue Jan 14 14:17:11 2003] ...
3978:   Child exiting at [Tue Jan 14 14:17:13 2003] ...
3977: Reaping a child process in child signal handler ...
3977: That was refreshing.  The time is now [Tue Jan 14 14:17:13 2003]
+.

[download]
From the documentation for sleep, May be interrupted if the process receives a signal such as "SIGALRM".

I can put the sleep in backticks, which seems to work albeit kludgily, but I am annoyed that putting it in backticks will result in a CHLD signal whenever the subprocess exits which means I have to worry about which child it was that exited when the child signal is caught.

My question to the monks is: How would those wiser in the ways of slumber do this?

In reply to Sleeping and reaping by Starky

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