Perl: Using Vars in Substitutions

cramer · 08-25-2006, 01:07 PM

I have the following code:

Code:

#!/usr/bin/perl5

#Read search for hlds_amd
$search=`ps ux | grep hlds_amd | grep -v grep`;
$user=`echo "\$USER"`;

#Get pid for hlds_amd
if ($search=~ m/(kimball   [0-9]{1,})/)
{
$amd_pid=$1;
print "\n$user\n";
$amd_pid=~s/\$user   //ge;
print "\n$amd_pid\n\n";
#system("kill $amd_pid");
}

I want to substitue the occurence of the username followed by 3 spaces by nothing (remove it). However, it seems the subsitution is not interpolating my variable $user. I have tried adding the e flag onto the end of the expression but it doesn't help.

demon_vox · 08-25-2006, 01:21 PM

Hi,
I think that the problem is that you are escaping the $. So Perl thinks he has to find $user literally, and thats not what you want. If you just write:

Code:

  s/$user   //ge

I believe its going to work.

Cheers!

cramer · 08-25-2006, 05:30 PM

Thanks, the problem was the way I was assigning the variable using ``.

demon_vox · 08-25-2006, 07:00 PM

Hi,
Perl also extrapolates variables in ` `, so, I didnt get what was the problem if it wasnt the escaped " (the \"$USER).

cramer · 08-25-2006, 07:41 PM

It wasn't getting the USER variable correct using the backticks.

Code:

$user=`echo "\$USER"`;

spirit receiver · 08-26-2006, 03:09 AM

There's no need for an external command like echo to get the username. The entire environment is accessible via the hash %ENV, and $ENV{USER} gives the username.

cramer · 08-26-2006, 12:52 PM

Oh, thanks

I'll have to do a foreach for the ENV hash and see whatelse I can get.
That's a big help. Thanks.
I was reading a perl book but it doesn't seem to cover that.