Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

I'm guessing that you want to "cut" the header lines out of the file, editing the file and leaving it with only the data in it. Here's the gradual evolution of something that will do that:

First off, we need to get a general plan. We want to read in the file line by line, and make a new file as we do so -- the trick is to not print the line if it's a header line. This means our new file will only have the data in it. So here's something that does that:

#!/usr/bin/perl -w; open IN, "file.in" or die "file.in: $!"; open OUT, ">file.out" or die ">file.out: $!" while (<IN>) { if ($_ =~ /^\d/) { print OUT $_; } } close IN; close OUT;

Next step is to make this code a little classier. First off, we can use the -n and -i command line options to make this a lot shorter. The -n does the work of the while loop, and the -i does the word of making a new file, and then replacing the original. It'll even keep a backup for you! Here's what it looks like using -ni, then:

#!/usr/bin/perl -ni.bak if ($_ =~ /^\d/) { print $_; }

..Which can be condensed and made a lot more canonical:

perl -ni.bak -e 'print if /^\d/' file.dat

Voila!

Update: Manythanks to ChemBoy. I said -ni in two places, then gradually drifted off to saying -pi. Oopsie.

perl -pe '"I lo*`+$^X$\"$]!$/"=~m%(.*)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'


In reply to Re: Re: Re: Extracting Header by Chmrr
in thread Extracting Header by raj8

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others pondering the Monastery: (6)
    As of 2014-11-27 21:14 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      My preferred Perl binaries come from:














      Results (188 votes), past polls