Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Language

Generated Code

use strict; my $str = '################################################################## #### /etc/apt/apt.conf.d/50unattended-upgrades ### // Automatically upgrade packages from these (origin:archive) pairs // // Note that in Ubuntu security updates may pull in new dependencies // from non-security sources (e.g. chromium). By allowing the release // pocket these get automatically pulled in. Unattended-Upgrade::Allowed-Origins { "${distro_id}:${distro_codename}"; "${distro_id}:${distro_codename}-security"; // Extended Security Maintenance; doesn\'t necessarily exist for // every release and this system may not have it installed, but if // available, the policy for updates is such that unattended-upgrades // should also install from here by default. "${distro_id}ESMApps:${distro_codename}-apps-security"; "${distro_id}ESM:${distro_codename}-infra-security"; // "${distro_id}:${distro_codename}-updates"; // "${distro_id}:${distro_codename}-proposed"; // "${distro_id}:${distro_codename}-backports"; }; // Python regular expressions, matching packages to exclude from upgrading Unattended-Upgrade::Package-Blacklist { // The following matches all packages starting with linux- // "linux-"; // Use $ to explicitely define the end of a package name. Without // the $, "libc6" would match all of them. // "libc6$"; // "libc6-dev$"; // "libc6-i686$"; // Special characters need escaping // "libstdc\\+\\+6$"; // The following matches packages like xen-system-amd64, xen-utils-4.1, // xenstore-utils and libxenstore3.0 // "(lib)?xen(store)?"; // For more information about Python regular expressions, see // https://docs.python.org/3/howto/regex.html }; // This option controls whether the development release of Ubuntu will be // upgraded automatically. Valid values are "true", "false", and "auto". Unattended-Upgrade::DevRelease "auto"; ################################################################## #### /etc/cron.weekly/man-db ### #!/bin/sh # # man-db cron weekly set -e if [ -d /run/systemd/system ]; then # Skip in favour of systemd timer. exit 0 fi iosched_idle= # Don\'t try to change I/O priority in a vserver or OpenVZ. if ! egrep -q \'(envID|VxID):.*[1-9]\' /proc/self/status && \\ ([ ! -d /proc/vz ] || [ -d /proc/bc ]); then iosched_idle=\'--iosched idle\' fi if ! [ -d /var/cache/man ]; then # Recover from deletion, per FHS. install -d -o man -g man -m 0755 /var/cache/man fi # regenerate man database if [ -x /usr/bin/mandb ]; then # --pidfile /dev/null so it always starts; mandb isn\'t really a daemon, # but we want to start it like one. start-stop-daemon --start --pidfile /dev/null \\ --startas /usr/bin/mandb --oknodo --chuid man \\ $iosched_idle \\ -- --quiet fi exit 0'; my $regex = qr/^((\s+|)(\/\/|#)|$)/mp; if ( $str =~ /$regex/g ) { print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n"; # print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n"; # print "Capture Group 2 is $2 ... and so on\n"; } # ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p' # Named capture groups can be called via $+{name}

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html