Beefy Boxes and Bandwidth Generously Provided by pair Networks
good chemistry is complicated,
and a little bit messy -LW
 
PerlMonks  

comment on

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

There's a couple of issues with your code that you should be aware of.

Firstly, when you slurp a file into a variable like that, the newline characters (\n) remain within the variable (i.e., you get exactly what was in the file).

To have your regular expression take that into account, you need to add a m alongside the g on the right-hand-side of the expression, which has Perl's regular expression engine match over multiple lines, rather than stopping when it hits the newline.

You can simplify the regular expression too to make your life a little easier. The following (working, but only partially tested) code snippet seems to do the job for me:

#! /usr/bin/perl use strict; use warnings; my $hn = 'localhost.localdomain'; my $hosts = `cat /etc/hosts`; if ( $hosts =~ /^([\d\.]+)\s+($hn)/mg ) { print "true: $1 $2\n"; } else { print "false!\n"; }
Having said that, there's almost certainly a better way to parse this file .. but I'm not caffienated enough to think of it at the minute.

Hope that helps!


In reply to Re: Passing variables into regular expressions by Tanalis
in thread Passing variables into regular expressions by wanderer

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!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • 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
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            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 musing on the Monastery: (7)
    As of 2020-12-02 22:23 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?
      How often do you use taint mode?





      Results (47 votes). Check out past polls.

      Notices?