CODEWITHSUNDEEP
arraysregexperlloops
user3423572
user3423572

Reputation: 559

Print regex match Perl

Hello I am in the process of making a program that matches a given set of keywords to a file.

I want to output the matched data to a text file and include the regex keyword that triggered the match.

Below is my code related to my issue:

my $counter = 0;
foreach($words) 
{
    while($line = <FILE>)
    {
        if($line =~ /$words/)
        {
            print "@array[$counter] $line\n";
            print OUTPUT $line;
        }
    }
    $counter ++;
}

This does not produce the expected outcome. It works perfectly for the first element in the array but for the rest it just simply prints the first one again. I believe the counter is not being incremented.

Is there a better / easier way to get the current element being used in the loop? or even get the current regex match?

Upvotes: 2

Views: 123

Answers (2)

7stud
7stud

Reputation: 48599

Here is what you should do:

use strict;
use warnings;
use 5.016;

my $fname = 'data.txt';

my @patterns = (
    'do.',
    '.at',
    '.ir.',
);

open my $INFILE, '<', $fname
    or die "Couldn't read from $fname: $!";

while (my $line = <$INFILE>) {
    for my $pattern (@patterns) {
        if ($line =~ /($pattern)/) {
            print "$pattern --> $1";
        }
    }
}

close $INFILE:

  1. Putting parentheses around parts of the regex causes perl to set the match variables $1, $2, $3, etc., which contain the match for each parenthesized group.

  2. $line will have a newline at the end of the line, so if you write print "$line\n", you will add another newline, so your output file will have blank lines between every line you print.

Upvotes: 1

choroba
choroba

Reputation: 241858

The problem is that <FILE> exhausts the file for the first word. For the next word, <FILE> tries to read at the end of the file, which means the whole loop is skipped.

You can iterate over the words inside the loop over the file, or you can seek back to the beginning of the file at the end of the loop.

Upvotes: 3

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