Regular Expression pattern storing in array

Question

I am new to perl and want to read a file in which IP are stored , i want to grep these IP and store in array , i am able to write the regex for this but out of three ips it always stores last ip of file in array , please help someone my code and file is like below.

my input file have follwing contents

Hi praveen how are10.23.54.86

10.87.98.65

10.98.76.54

my script o/p is

/pearl$ ./par.pl sdp.txt

10.98.76.54

and code is

#!/usr/bin/perl

open (INPUT,$ARGV[0]) || die "Can not open file:$!";

$i=0;

while(<INPUT>)
{
  $line=$_;
  ($arr,$arr1,$arr2)=($line=~m/\d+[\.]\d+[\.]\d+[\.]\d+/g);
}


close(INPUT);

print $arr,"\n";

I tried with array and as well as variable but same results its only stores last value.

I'm a Java developer so maybe I'm bringing the wrong idiom to this Perl question: aren't you supposed to declare/initialize your arr BEFORE the while loop and inside just accumulate the result? — targumon
– targumon, Commented Nov 6, 2012 at 13:39
@targumon That's optional in perl, it's good practice to use strict in longer scripts in which case you would have to do that. However perl supports one liners were it's nice to have auto initialization by default. — Benj
– Benj, Commented Nov 6, 2012 at 13:42
@Benj it is optional, but it should be done in general. This is not a one-liner, so strict and warnings should be enabled. — simbabque
– simbabque, Commented Nov 6, 2012 at 14:13

sidyll · Accepted Answer · 2012-11-06 13:50:34Z

2

As you're reading one line at a time, and each line has only one address, of course you have only one output since the output is printed after the loop, not inside it on each iteration.

Use <>
Avoid unecessary variables (like $i)
Enable warnings
You most likely want to use an array to store your IPs

In the following code, your IPs will be stored in @ips.

#!/usr/bin/perl

use warnings;
use strict;

my @ips;

while (<>) {
    # not the optimal regex for IPs, I just simplifyied yours
    push @ips, m/(?:\d+\.){3}\d+/g;
}

print "@ips\n";
# --- or ---
print "$_\n" foreach @ips;

edited Nov 6, 2012 at 13:50

answered Nov 6, 2012 at 13:43

sidyll

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Comments

Kenosis · Accepted Answer · 2012-11-06 16:41:33Z

1

Consider using the Perl Module Regexp::Common to match the IPs, as it's been well-developed for this purpose:

use strict;
use warnings;
use Regexp::Common qw/net/;

my @IPs;

while (<>) {
    my ($IP) = /($RE{net}{IPv4})/;
    push @IPs, $IP if $IP;
}

print "$_\n" for @IPs;

Output from your data set:

10.23.54.86
10.87.98.65
10.98.76.54

A valid IP on a line is captured and placed into $IP. The next line pushes an IP onto @IPs if $IP contains one. Finally, the elements of @IPs are printed, if any.

Hope this helps!

answered Nov 6, 2012 at 16:41

Kenosis

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Comments

sidyll · Accepted Answer · 2012-11-06 14:13:57Z

0

You appear to have two problems:

You appear to be filling 3 variables, not 4 (Unless you don't want the last number?)
Your regex doesn't specify any capture groups so you're not saving out any values from the matched string.

You want something like:

while(<INPUT>)
{
  if( ($arr,$arr1,$arr2,$arr3) = /(\d+)\.(\d+)\.(\d+)\.(\d+)/g )
  {
    print "$arr $arr1 $arr2 $arr3\n";
  }
}

Or if you want to treat the matched numbers as a list try this:

while(<>)
{
  chomp;
  if( @array = /(\d+)\.(\d+)\.(\d+)\.(\d+)/g )
  {
    print @array;
  }
}

edited Nov 6, 2012 at 14:13

sidyll

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answered Nov 6, 2012 at 13:36

Benj

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1 Comment

sidyll Over a year ago

@fxzuz Never ever edit a question to change its indentation style, that is completely personal; and unless it's not readable, it won't contribute to anything.

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