Perl parsing config file with regex to key, value

Question

I have come up with the following, to first read the file and then put it into hash. = sign used as a delimiter.

sub get_config_value_by_key {
    my ( $module, $key ) = @_;

    my $config = &read_file_contents(
        $config_directory . '/' . $module . '/config' );
    my %config = $config =~ /(.*)=(.*)/g;

    return $config{$key};    
}

It works fine, except that, if I have equal sign in the value (which I use as delimiter), then it doesn't parse it correctly.

How to fix my regex to make it work properly, escaping = signs in the value?

Example of config lines:

key_1=Some value key_2=Some value with = sign which breaks it.

Don't use & when calling functions... it's so unneeded! Then, unless you have to solve this for homework or golfing, I'd look into split instead of solving it all with a single regexp. — polettix, Jan 09 '16 at 10:08
@polettix No, not the home work, I do this for my _Authentic Theme_ (for Webmin). Webmin uses `&` in front of functions a lot. I'm not Perl expert yet. Why is `&` used for? — Ilia Ross, Jan 09 '16 at 10:16
`Re: &` please check http://stackoverflow.com/questions/8912049/difference-between-function-and-function-in-perl — mpapec, Jan 09 '16 at 10:50
Summary is though: Only do it if you have a specific reason to. And even then, consider not doing so anyway, because it's probably less clear. — Sobrique, Jan 09 '16 at 10:52

score 3 · Accepted Answer · answered Jan 09 '16 at 10:43

3

You can use non greedy quantifier,

my %config = $config =~ /(.*?)=(.*)/g;
                          # ^_________ match smallest possible amount of chars

answered Jan 09 '16 at 10:43

mpapec

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I'd also not bother slurping config into an intermediate variable. This works just as well with `<$fh> =~ m/([^=]+)=(.*)/g;` (slightly different LHS, but that's a matter of taste) – Sobrique Jan 09 '16 at 10:49
1

Yeah, I know. I just assumed that was what `read_file_contents($filename);` was doing. – Sobrique Jan 09 '16 at 10:52
I'll check in a bit. Thanks, guys! – Ilia Ross Jan 09 '16 at 10:59
@Сухой27 Thanks, pal! However I don't understand why. What this `?` really does? – Ilia Ross Jan 09 '16 at 11:42
@IliaRostovtsev it makes a regex lazy (stop matching at first `=` occurrence) http://stackoverflow.com/a/2301298/223226 – mpapec Jan 10 '16 at 08:32

fugu · Answer 2 · 2016-01-09T10:45:25.373

2

I would use something like this:

use warnings;
use strict; 
use Data::Dumper;

open my $in, '<', 'in.txt' or die $!;

my %data;
while(<$in>){
    my($key, $val) = split(/=/, $_, 2);  
    $data{$key} = $val; 
}

print Dumper \%data;

This will read in a file - here in.txt, split each line on = into a maximum of two parts, and then assign them to a hash key/value pair.

However your approach could be tweaked to allow non-greedy matching (.*?):

while(<$in>){   
    my ($key, $val) = $_ =~ /(.*?)=(.*)/;
    $data{$key} = $val;
    }

edited Jan 09 '16 at 10:45

answered Jan 09 '16 at 10:27

fugu

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`split(/=/,` will split on second or third `=` sign in the line, right? I would like to see how my regex could be fixed. – Ilia Ross Jan 09 '16 at 10:30
@IliaRostovtsev - this should preserve the value string, as it only splits into two parts, and will stop after encountering the first `=` – fugu Jan 09 '16 at 10:34

Perl parsing config file with regex to key, value

2 Answers2