Can I have a Perl script, initiated from a browser, fork itself, and not wait for the child to end?

Question

Also posted on PerlMonks.

I have this very simple Perl script on my linux server.

What I would like to be able to do is to call the script from a browser on a separate machine
Have the script initiate a fork
Have the parent send an httpResponse (freeing up the browser)
Immediately end the parent
Allow the child to do its job, heavy complex database work, which could take a minute or two
Have the child end itself with no output whatsoever

When I call this script from a browser, the browser does not receive the sent response till the child is complete.

Yes, it works when called from the command line.

Is what I want to do possible? p.s. I even tried it with ProcSimple, but I get the same hang up.

#!/usr/bin/perl
local $SIG{CHLD} = "IGNORE";
use lib '/var/www/cgi-bin';
use CGI;

my $q = new CGI;

if(!defined($pid = fork())) {
   die "Cannot fork a child: $!";
} elsif ($pid == 0) {
   print $q->header();
   print "i am the child\n";
   sleep(10);
   print "child is done\n";
   exit;
} else {
    print $q->header();
    print "I am the parent\n";
       print "parent is done\n";
   exit 0;
}
exit 0;

Answer 1

In general you must detach the child process from its parent to allow the parent to exit cleanly -- otherwise the parent can't assume that it won't need to handle more input/output.

} elsif ($pid == 0) {
   close STDIN;
   close STDERR;
   close STDOUT;   # or redirect
   do_long_running_task();
   exit;

In your example, the child process is making print statements until it exits. Where do those prints go if the parent process has been killed and closed its I/O handles?