Removing comments

Not working...

[adni18]

Hi. I want to use a regexp to remove everything in #'s. How can this be done?

Ex:

hello there #remove remove this, and this remove this#
don't remove anything until #now#

[IanKelley]

$var =~ s/#[^#]+#//g;

[kaled]

I use the following to remove a comment from a line :-

$line =~ s/#.*//;

Kaled.

[IanKelley]

That will remove everything after 'hello there'

[wruppert]

$var =~ s/#[^#]+#//g;

This is too greedy, it consumes everything from the first # to the last one. Also, I don't think it will remove two adjacent #'s because of using + instead of *.

I would replace the [^#]+ with [^#]*?. The? causes the * quantifier to do a minimal match.

$var =~ s/#[^#]*?#//g;

[IanKelley]

If you had actually tested it, you'd know that's not true. ;-)

[^#]+

is incapable of matching anything after the first # it encounters.

[wruppert]

Ian,

You're right, I was wrong about the greediness of that pattern. The '?' is not needed in this case.

However (after testing this time!), I did find that the + does not correctly handle empty comments (##), while the * does.

use strict;
use warnings;
my $var1 = "hello #remove this# don't remove ## until #now# ";
$var1 =~ s/#[^#]*#//g; 
print $var1;
print "\n";
my $var2 = "hello #remove this# don't remove ## until #now# ";
$var2 =~ s/#[^#]+#//g; 
print $var2;

Produces the output:

hello don't remove until 
hello don't remove #now# 

[IanKelley]

Yes, good point, if there's any chance of empty comments it's best to use * instead of +