Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Can someone tell me how I would go about taking a number like 0111 or 0248 and only take the LAST two digits and somehow put the last two numbers inside a scalar so I an use it? All the sets of numbers are four digits.

Thanks for your help, monks.

janitored by ybiC: Retitle from less-than-descriptive "Regex needed"

Replies are listed 'Best First'.
Re: Extract last two digits from numbers
by Limbic~Region (Chancellor) on Jan 06, 2004 at 10:10 UTC
    Anonymous Monk,
    There are lot's of ways to do this - you might want to consider taking a look at perldoc perlre. 
    #!/usr/bin/perl -w
use strict;

my $number = 1234;
my $last2;
if ( $number =~ /^\d\d(\d\d)$/ ) {
    $last2 = $1;
}
print "$last2\n" if defined $last2;

    [download]
    Cheers - L~R

    Update: Regular expressions can be tricky as can be the notion of what constitutes a "number". You might also want to take a look at Mastering Regular Expressions and Scalar::Util's looks_like_number function for some more advanced stuff.

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[d/l]
Re: Extract last two digits from numbers
by tachyon (Chancellor) on Jan 06, 2004 at 10:10 UTC 
    my ($digits)= $str =~ m/\d\d(\d\d)/;

    [download]

    cheers

    tachyon

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[d/l]
Re: Extract last two digits from numbers
by CountZero (Bishop) on Jan 06, 2004 at 10:39 UTC
    No need to use a regex: $lasttwo=substr($number,-2,2)

    And it works for any length of number. It works even for non-numerical strings (Is that a bug or a feature?)

    CountZero

    "If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

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[d/l]

      There is no need for the third parameter there 

      my $s= '12345';
print substr $s, -2;

45

      [download]

      Of course, it doesn't hurt either :)

      Examine what is said, not who speaks.
      "Efficiency is intelligent laziness." -David Dunham
      "Think for yourself!" - Abigail
      Hooray!
[reply]
[d/l]
Re: Extract last two digits from numbers
by yosefm (Friar) on Jan 06, 2004 at 10:13 UTC
    Assuming the number is at the end of the variable being matched, use: /\d{2}$/. the '\d' means match digits, the '{2}' means two exactly, and the '$' means end of line. Other option: /\d\d$/ (simpler).

    Update: Note that L~R's regex is more specific (putting '^' first means start of line) while tachyon's regex is more relaxed, finding any 4 digit number and capturing its last two digits (using parentheses).

    Another update: See L~R's reply below.

[reply]
      yosefm,
      finding any 4 digit number and capturing its last two digits

      Just to be clear, tachyon's regex will match the last two digits of the first set of digits in a string that are at least 4 digits long

    • "The cat 1234567 in the hat"
    • 1234
    • "Just like 3456789 he was 12345"

      Cheers - L~R

      Update: As duff points out below, I am an idiot. My above statement would be correct if the regex had been /\d\d(\d\d)\b/

[reply]
        Just to be clear, tachyon's regex will match the last two digits of the first set of digits in a string that are at least 4 digits long

        That's not clear at all because that's not what his regular expression does. What it does is match the second pair of the first sequence of 4 digits within a string. Here's tachyon's code again: my ($digits)= $str =~ m/\d\d(\d\d)/; and here is what your examples should have looked like:

        • "The cat 1234567 in the hat"
        • 1234
        • "Just lie 3456789 he was 12345"

        duff

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[d/l]
Re: Extract last two digits from numbers
by BrowserUk (Patriarch) on Jan 06, 2004 at 11:13 UTC

    If you know that your numbers are numbers, then there's no need to use a regex, just math. 

    my $number = '0234';
$number %= 100;
print $number;

34

    [download]
    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "Think for yourself!" - Abigail
    Hooray!
[reply]
[d/l]
      my $number = '3204';
$number %= 100;
print $number;

4

      [download]

      Abigail

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[d/l]

        Good point. I guess it depends on whether the OP wants two characters or the numeric value of the last two digits.

        Without clarification, my interpretation is probably the least likely given context.

        Examine what is said, not who speaks.
        "Efficiency is intelligent laziness." -David Dunham
        "Think for yourself!" - Abigail
        Hooray!
[reply]

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