Solved

Perl code to remove duplicate lines from text file

Posted on 1998-10-10
3
1,014 Views
Last Modified: 2008-03-17
Ok, I need a quick Perl script that can take a sorted text file and remove duplicate lines and my brain is too fried to write this myself so I'm hoping someone can save me some time.

I have a text file (mailing list) which consists of two fields per line: <email> (space as delimiter) (person's name in parenthesis) - I need a routine to read the text file and remove duplicates in the first field.

I'll also award points if someone can give you a unix solution to this.

This needs to handle a 12,000+ line text file and be case insensitive (in determining dupes).
0
Comment
Question by:wisdom042597
3 Comments
 
LVL 1

Author Comment

by:wisdom042597
Comment Utility
As a plus, it would be nice to reject any e-mail field which doesn't contain the '@' symbol.

0
 
LVL 84

Expert Comment

by:ozo
Comment Utility
perldoc perlfaq4
  How can I extract just the unique elements of an array?

            There are several possible ways, depending on whether
            the array is ordered and whether you wish to preserve
            the ordering.

    a) If @in is sorted, and you want @out to be sorted:
    (this assumes all true values in the array)
                    $prev = 'nonesuch';
                    @out = grep($_ ne $prev && ($prev = $_), @in);

                This is nice in that it doesn't use much extra
                memory, simulating uniq(1)'s behavior of removing
                only adjacent duplicates. It's less nice in that it
                won't work with false values like undef, 0, or "";
                "0 but true" is ok, though.

    b) If you don't know whether @in is sorted:
                    undef %saw;
                    @out = grep(!$saw{$_}++, @in);

    c) Like (b), but @in contains only small integers:
                    @out = grep(!$saw[$_]++, @in);

    d) A way to do (b) without any loops or greps:
                    undef %saw;
                    @saw{@in} = ();
                    @out = sort keys %saw;  # remove sort if undesired

    e) Like (d), but @in contains only small positive integers:
                    undef @ary;
                    @ary[@in] = @in;
                    @out = @ary;

  How can I get the unique keys from two hashes?

            First you extract the keys from the hashes into arrays,
            and then solve the uniquifying the array problem
            described above. For example:

                %seen = ();
                for $element (keys(%foo), keys(%bar)) {
                    $seen{$element}++;
                }
                @uniq = keys %seen;

            Or more succinctly:

                @uniq = keys %{{%foo,%bar}};

            Or if you really want to save space:

                %seen = ();
                while (defined ($key = each %foo)) {
                    $seen{$key}++;
                }
                while (defined ($key = each %bar)) {
                    $seen{$key}++;
                }
                @uniq = keys %seen;

0
 

Accepted Solution

by:
pcrutch earned 200 total points
Comment Utility
Here's the unix solution..

 sort -fu -t' ' -k 0 -o <textfile> <textfile> | \
   grep '^\w+\@\w+ '

As for the perl, here is a solution for either unix or Win32:
----
# Read in each line from STDIN or filename on cmd line
while(<>) {
  chomp;
  # Push it onto the text array
  push(@text);
}

# Loop through the sorted text array
foreach $line (sort @text) {
  # Split the line into fields
  ($email,$name) = split(' ',$line);

  # email has embedded '@'?
  next if (! $email =~ /\@/);

  # @nodup will contain no-duplicate emails
  if (! @nodup =~ /$email/i) {
    print '$email $name\n';
    push(@nodup,$email);
  }
}
----
Note this will print the first email/name pair of duplicate fields.

0

Featured Post

What Security Threats Are You Missing?

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

Join & Write a Comment

Many time we need to work with multiple files all together. If its windows system then we can use some GUI based editor to accomplish our task. But what if you are on putty or have only CLI(Command Line Interface) as an option to  edit your files. I…
Checking the Alert Log in AWS RDS Oracle can be a pain through their user interface.  I made a script to download the Alert Log, look for errors, and email me the trace files.  In this article I'll describe what I did and share my script.
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Illustrator's Shape Builder tool will let you combine shapes visually and interactively. This video shows the Mac version, but the tool works the same way in Windows. To follow along with this video, you can draw your own shapes or download the file…

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

11 Experts available now in Live!

Get 1:1 Help Now