Fetch particular line content from file stored in an array

Question

I have a file, and I need to take a count value from the file.

I am storing all the contents of the file in an array and later searching for that particular line (Total number of lines in file is). And again using regex, I am taking out the count.

Code below:

#!/usr/bin/perl

use Data::Dumper;

my @array = <DATA>;

print Dumper(\@array);

my $count = 0;

my @matches = grep { /Total number of lines in file is/ } @array;

foreach (@matches){
    $count = $1 if($_ =~ /Total number of lines in file is :\s*(\d+)\s*/);
}

print "Count:$count\n";

__DATA__
Below is your data file

This is test line A
This is test line B
This is test line C
This is test line D
This is test line E
This is test line F
This is test line G
This is test line H
This is test line I
This is test line J

Total number of lines in file is :10

Here I am using grep and for loop to take the count which is needed to me.

Is there any better way to do this? So, using single grep I can take the count.

choroba · Accepted Answer · 2020-06-08 11:56:13Z

2

If you don't need to retain all the lines, and you are just interested in the matching line, you can simplify it to:

use warnings;
use strict;

my $count = 0;
while (<DATA>) {
    $count = $1 if /Total number of lines in file is :\s*(\d+)\s*/;
}
print "Count:$count\n";

edited Jun 8, 2020 at 11:56

choroba

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answered Jun 8, 2020 at 11:48

toolic

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Comments

ssr1012 · Accepted Answer · 2020-06-08 14:04:49Z

0

Let's find it in another way:

my $str = do { local $/; <DATA>; };

print $1 if($str=~m/Total number of lines in file is :(\d+)/);

edited Jun 8, 2020 at 14:04

answered Jun 8, 2020 at 13:42

ssr1012

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1 Comment

simbabque Over a year ago

This will return the entire line once for every line that matched the pattern and had a number that isn't 0 in the capture group. For the example input that should be 1. That's because grep doesn't map, it just throws away elements where the test returns false.

bittrine · Accepted Answer · 2020-06-08 14:40:20Z

-1

if you are so keen to use grep instead of toolic's approach, use system grep or backticks :) but you need to understand that firstly you read whole file in an array, and then you "grep" (loop through) all array items and check whether they match the regex. basically, you do the same but with additional memory waste

answered Jun 8, 2020 at 14:40

bittrine

1

2 Comments

vkk05 Over a year ago

Agree!! I don't want to waste memory to do this operation.

brian d foy Over a year ago

You don't need to read in the entire file, or shell out to anything.

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