extracting data from an input file and associated errors

rakshas has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I have the following format of data in a text file. I can successfully read it from the file ___________________________________________________________
-rw-r--r-- 1 next users 2153 Jan 1 10:50 mytake_120.115.152.136.csv
___________________________________________________________
I want to extract "120.115.152.136" and use it so I wrote the following script.
_________________________________________________________

use strict;
use warnings;

print "\nEnter the Model 1\n";
my $Model_Name1= <STDIN>;
chomp $Model_Name1;

open (DATA, "< C:/Perl_Scripts/InputFile.txt"); 
my @array_of_data = <DATA>;
close (DATA);

foreach my $line (@array_of_data)
{
  
if ( $line =~ m/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\.csv$/g )

{
      print "Match $1";
}
}
[download]

As I have said earlier, I want to extract "120.115.152.136", hence I am using the regex. It just prints "Match" but also gives an error Use of uninitialized value $_ in pattern match (m//) at C:\Perl_Scripts\Compare.pl line 31. Any Help will be much appreciated. Regards Vivek

Comment on extracting data from an input file and associated errors Download Code

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Re: extracting data from an input file and associated errors by jwkrahn (Abbot) on Feb 02, 2012 at 23:47 UTC
`open (DATA, "< C:/Perl_Scripts/InputFile.txt");` [download] You should verify that open worked correctly: `open my $DATA, '<', 'C:/Perl_Scripts/InputFile.txt' or die "Cannot ope +n 'C:/Perl_Scripts/InputFile.txt' because: $!";` [download] `my @array_of_data = <DATA>; close (DATA); foreach my $line (@array_of_data) {` [download] There is no need to read the entire file into memory first: `while ( my $line = <$DATA> ) {` [download] `if ( $line =~ m/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\.csv$/g ) { print "Match $1"; }` [download] The pattern is anchored at the end of the line so the /g option is superfluous. You are not using capturing parentheses in the pattern so there is nothing in $1 to print out.	[reply] [d/l] [select]
Re: extracting data from an input file and associated errors by chilledham (Friar) on Feb 02, 2012 at 23:42 UTC
You need to capture the match you want: `$line =~ m/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\.csv$/g` The match in your first set of parens will be stored in `$1`, in the second set of parens in `$2`, and so on. See `perldoc perlretut`.	[reply] [d/l] [select]