Variable doesn't hold proper value

hawk__0 · 01-06-2010, 01:11 PM

I was creating a script and I can't figure out why this isn't working....

Code:

my $priv = system "whoami";
if ($priv ne "root"){
	say "FATAL ERROR: you may only run this as root.  User found running script: $priv";
	die;
}

when I try to execute it, this happens:

Code:

root
FATAL ERROR: you may only run this as root.  User found running script: 0
Died at hostcheck.pl line 42.

Why is my value changed to 0? It's like it's checking it as a scalar value...

alunduil · 01-06-2010, 01:20 PM

The system function simply runs the code. What's returned is the return value of the utility. In this case if you print $priv it will be a 0 for success. Try using popen or another pipe function that lets you treat your subprocess as a file.

Regards,

Alunduil

devnull10 · 01-06-2010, 01:39 PM

Why not just use the function getlogin()?

Code:

#!/usr/bin/perl

print "Your username is " .getlogin();

hawk__0 · 01-06-2010, 03:42 PM

I am new to perl, had no idea that function existed. I'll sue that, thanks!

edit:

getlogin(); wont work for me. It's tied to my login session somehow. I would like to be able to sudo this script, or use su to switch my user from a terminal. It always returns my regular login

devnull10 · 01-06-2010, 04:04 PM

Well, you know root will be userid 0, so you could use $<:

Code:

#!/usr/bin/perl

print "User id of current user is $< \n"

This works with su however I haven't tried it with sudo - I can't see why it wouldn't.

hawk__0 · 01-06-2010, 04:23 PM

that works, thanks!

PMP · 01-07-2010, 01:55 AM

That's great it worked.

For your issue

Code:

 
my $priv = system "whoami";
if ($priv ne "root"){
	say "FATAL ERROR: you may only run this as root.  User found running script: $priv";
	die;
}

This will work as well, you need to collect the output of "whoami" in the variable.

Code:

my $priv = `whoami`;
chomp($priv);
if ($priv ne "root"){
	say "FATAL ERROR: you may only run this as root.  User found running script: $priv";
	die;
}

Mind the backticks in the whoami command they are not single quote.