How can I extract multiple email addresses from a single line using a Perl regex?

Question

Hello,

I have a text file which was originally a mysql dump of a database table. How do I write a Perl script to extract all the email addresses from this text file?

The problem I am having is that I read in the lines of the document one by one then do a regular expression, however in cases where there are more than one email address on the same line my script seems to fail.

open (FP, '<my-large-file.txt');
  while($line = <FP>)
  {
      #if($line =~ /\s([\S]{1,80}[@]{1}[\S]{2,100})\s/)
      #if($line =~ /([\S]{1,80}[@]{1}[\S]{2,100})\s/)
      #if($line =~ /([\S]{1,80}[@]{1}[\S]{2,100})[,]/)
      {
          push(@emails, $1);
      }
  }
close (FP);

I have been playing with the above code but did not get the desired outcome.

Answer 1

assuming your regex itself is correct, to match more than once, place the g modifier at the end to match multiple times, and then return the list. Your code then looks something like this:

open (FP, '<my-large-file.txt');
  while($line = <FP>)
  {
      push @emails, $line =~ /your_regex_here/g;
  }
close (FP);

Answer 2

Use the /g modifier to match a regular expression multiple times:

open (FP, '<my-large-file.txt');
while($line = <FP>)
{
  my @matches = /(\S{1,80}@\S{2,100})\s/g;
  push @emails, @matches;
}
close (FP);

Answer 3

I think one of posible falure is using \s instead of \b. Try following condition:

if($line =~ /\b([\S]{1,80}[@]{1}[\S]{2,100})\b/)

Also always check if file is opened successful. And use strict/warnings:

use strict;
use warnings;
open (FP, '<my-large-file.txt') or die "can't open file: $!";

Answer 4

Hi Sounds like you're happy with the regex but just need to capture multiple matches.

To do that, you need to stop using if and use the /g modifier.

Additionally, if the file is small enough, you could then read the whole file into a single string since you are able to deal with multiple matches now.

Here is an example:

use strict;
use warnings;

open my $fh, '<', 'my-large-file.txt' or die "Open error: $!";
my $contents = do { local $/;  <$fh> }; # read the whole file

my @emails;
push @emails, $contents =~ /emailpattern/g;

The matches are returned in the array context, so don't need capturing parens or $1 either.

Answer 5

assuming email addr are one word by itself separated by spaces, no need for too much regex

while (<>){
  chomp;
  @s = split /\s+/ ;
  foreach my $i (@s){
    print $i ."\n" if $i =~ /@/;
  }
}

Answer 6

Ivan Nevostruev's answer has flaws.

#!/usr/bin/perl

open (FP, '<my-large-file.txt');
while($line = <FP>)
{
   my @matches = /(\S{1,80}@\S{2,100})\s/g;
   push @emails, @matches;
}
close (FP);

This will not work because @matches is matching against $_, which will not exist because <FP> is being read into $line. Also, imho, creating two array symbols (one from the other) seems poorly implemented. It seems better to me to create one symbol from the resulting list and that one symbol being the container for all of the data you need. See below for my example.

* Here's a nice link for an email regex http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html. I recommend working it in something like this (over-kill? Yeah, probably (:):

#!/usr/bin/perl -w

use strict;

open(F,'<your_file.dump')
    or die('Nope: '.$!);
my $re = 
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'*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])'.
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'?:\r\n)?[ \t])*))*)?;\s*)/mig';
my @all;

while ( chomp(my $line = <F>) )
{
    push(@all,$line =~ qr($re));
}

close(F);