CODEWITHSUNDEEP
perlapacheunixcgisignals
Pranav Pal
Pranav Pal

Reputation: 275

Stopping httpd causes a process started from perl CGI script to receive SIGTERM

I am running a shell script from a perl CGI script:

#!/usr/bin/perl
my $command = "./script.sh &";
my $pid = fork();
if (defined($pid) && $pid==0) {
        # background process
        system( $command );
}

The shell script looks like this:

#!/bin/sh
trap 'echo trapped' 15
tail -f test.log

When I run the CGI script from browser, and then stop httpd using /etc/init.d/httpd stop, the script receives a SIGTERM signal.

I was expecting the script to run as a separate process and not be tied in anyway to httpd. Though I can trap the SIGTERM, I would like to understand why the script is receiving SIGTERM at all.

What wrong am I doing here? I am running RHEL 5.8 and Apache HTTP server 2.4.

Thanks, Pranav

Upvotes: 1

Views: 348

Answers (1)

innaM
innaM

Reputation: 47909

The process you are spawning still has httpd's parent PID attached to it. So this might work:

use POSIX qw / setsid /;
...
my $command = "./script.sh";
my $pid = fork();
if (defined $pid && $pid == 0) {
    close *STDIN;
    close *STDOUT;
    close *STDERR;
    setsid;
    system( $command );
    exit 0;
}

And since it doesn't sound like your process should ever return back to your script, you might even do

use POSIX qw / setsid /;
...
my $command = "./script.sh";
my $pid = fork();
if (defined $pid && $pid == 0) {
    close *STDIN;
    close *STDOUT;
    close *STDERR;
    setsid;
    exec( $command );
}

Upvotes: 1

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