I'm sure there's an easy way around this with fork, but rather than guess at the answer, I'll just present the problem (I've been trying to solve this for a bit).

#!/usr/bin/perl

use strict;
use warnings;

eval {
    local $SIG{ALRM} = sub { die "alarm\n" };
    alarm 2;
    system("perl -e '1 while 1'") == 0
      or die "Cannot do infinite loop: $!";
    alarm 0;
};
die $@ unless $@ eq "alarm\n";

# the following lines let me do a 'ps awux|grep perl' 
# while this is running
print 'Hanging ...';
<STDIN>;

[download]

I don't do a huge amount of work with process management, so this is giving me fits. Basically, I sometimes need call code code which may never return but I have no way of knowing in advance if this is the case. I want an alarm to catch when that happens. However, when I do that, the proces is hanging around in the process table. How can I ensure that when the system times out that the process is reaped? I'm making about 10,000 system calls and this is rapidly killing my system.

Update:

I forgot that this isn't a real example of what I need. I also need the result, if any, of the command I execute. My actual code looks like this:

sub timeout {
    my ( $package, $timeout, $code ) = @_;

    my $result;
    eval {
        local $SIG{ALRM} = sub { die "alarm\n" };    # NB: \n required
        alarm $timeout;
        $result = $code->();
        alarm 0;
    };
    if ($@) {
        die "Could not make $package: $@" unless $@ eq "alarm\n";    #
+ propagate unexpected errors
                                       # timed out
    }
    return $result;
}

timeout( $package, 10, sub {`perl $make_prog 2>&1`} );

[download]

Cheers,
Ovid

New address of my CGI Course.

In reply to Killing a hanging child process by Ovid

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