in reply to Is this a bug in perl regex engine or in my brain?

I'd be inclined to do it like this: 
while (<>) {
    chomp;
    my $result = ( /^([1-9]\d*)$/ and $1 < 256 ) ? "matched" : "did no
+t match";
    $_ .= " $result\n";
    print;
}

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That rejects anything with a leading zero (hence "0"), and anything greater that 255.

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Re^2: Is this a bug in perl regex engine or in my brain? (matching from 0 to 255)
by Discipulus (Canon) on Oct 07, 2015 at 07:28 UTC
    I very like this approach. It saves us from the "I had aproblem, i used a regex, now i have two problems" situation.
    If you (the OP) want a review of most possible implications concerning the parsing of an IP address (numbers from 0 to 255 are an octet of an IP address expressed in the dotted decimal form) you can read some paragraph of "Mastering regular expressions" where the proposed result is: 
    
      [01]?\d\d?|2[0-4]\d|25[0-5]

    [download]
    on the same argument you can find interesting an old thread: Don't Use Regular Expressions To Parse IP Addresses! or some exaples on another site.

    Regex::Common::net is used for the exact purpose and if you feel strong you can dive in it's source code to see how to match an octet.

    L*
    There are no rules, there are no thumbs..
    Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.
[reply]
[d/l]

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