Re: Why won't it die??

I can't actually help with your real question, I'm afraid. I want to toss in some pointers though. See comments.

#!/usr/bin/perl -wT
use strict;

$ENV{PATH} =
'/bin:/usr/bin:/usr/bin/X11:/usr/local/bin:/usr/bin:/usr/X11R6/bin';

my @process = `ps -u me`; # only call ps(1) once

if (grep /ircd/, @process) { # use Perl's builtin grep
    print "Ircd is up!\n";
}
else {
    print "Starting Ircd......\n";
    # use system(LIST) rather than backticks
    system qw(sudo -u dsirc /home/me/Unreal3.1.4/src/ircd)
        or die "Failed to launch ircd!\n";
}

if (grep /wrecked/, @process) {
    print "Services are up!\n";
}
else {
    print "Starting Services......\n";
    system qw(sudo -u dsirc /home/me/services/wrecked)
        or die "Failed to launch services!\n";
}
[download]

Update: added checks for system success.

Makeshifts last the longest.

Comment on Re: Why won't it die?? Download Code

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Re: Re: Why won't it die?? by Anonymous Monk on Aug 22, 2002 at 03:12 UTC
Thanks for the pointers Aristotle! I see all your points. Safer to make system calls with the built in function, rather than the backtic? And storing both ps calls into one aray is less code, so its slightly faster(and prettier to boot)??	[reply]
Re^3: Why won't it die?? by Aristotle (Chancellor) on Aug 22, 2002 at 03:32 UTC
Using system is a question of economy here. With the backticks, you capture the command's output - only to throw it away. The `system(LIST)` form also avoids invoking the shell. Actually, if you were interpolating user input into the call, avoiding the shell via `system(LIST)` increases security as well, because you don't have to worry about shell metacharacters, but that's not the case here. The benefit of storing the output from `ps` is twofold. First of all, you only need to call the program once, as opposed to twice. And then you can use Perl's own grep to search that data - as opposed to spawning a process for the `grep` binary, twice. What grep really returns is a list of all the list that matched, but we're not storing it. Using a list in an `if` condition simply checks if the list is empty or not, and that's what we do here. Btw, have another look at the post. The first time around, I forgot another detail: I wasn't checking for whether the `system` calls succeed. Stupid omission now fixed.. Makeshifts last the longest.	[reply]