2013/02/26

Visualization of Regular Expression Character Classes - good coders code, great reuse

Visualization of Regular Expression Character Classes

Posted: 25 Feb 2013 11:28 AM PST

We all know the regular expression character classes, right? There are 12 standard classes:

  [:alnum:]  [:digit:]  [:punct:]  [:alpha:]  [:graph:]  [:space:]  [:blank:]  [:lower:]  [:upper:]  [:cntrl:]  [:print:]  [:xdigit:]

But have you seen a visual representation of what these classes match? Probably not. Therefore I created a visualization that illustrates which part of the ASCII set each character class matches. Call it a cheat sheet if you like:

small version, large version

A bunch of programs that I used

Just for my own reference, in case I ever need them again, here are the one-liners I used to create this cheat sheet:

  perl -nle 'printf "%08b - %08b\n", map { hex "0x".(split / /)[0], hex "0x".(split / /)[1] } $_ '  perl -nle 'printf "%03o - %03o\n", map { (split / /)[0], (split / /)[1] } $_'

And I used this perl program to generate and check the red/green matches:

use warnings;  use strict;    my $red = "\e[31m";  my $green = "\e[32m";  my $clear = "\e[0m";    my ($start, $end) = @ARGV;    die 'start or end not given' unless defined $start && defined $end;    my @classes = qw/alnum alpha blank cntrl digit graph lower print punct space upper xdigit/;    for (map { chr } $start..$end) {      for my $class (@classes) {          print "${green}1${clear}" if /[[:$class:]]/;          print "${red}0${clear}" unless /[[:$class:]]/;      }      print "\n"  }