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

/
/
g

Test String

Code Generator

Language

Generated Code

use strict; my $str = 'Dec 25 21:44:10 ra-mx amavis[69766]: (69766-04) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T202928-69766-zqjUPXL8: <notification+kr4keges24xr@facebookmail.com> -> <sto@kingkong.network> SIZE=21892 BODY=8BITMIME Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <sto@kingkong.network>; Sun, 25 Dec 2016 21:44:10 +0100 (CET) Dec 25 21:47:27 ra-mx amavis[67599]: (67599-13) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T182139-67599-Iw5AO2Ei: <> -> <bounce@espeurope.net> SIZE=25924 Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <bounce@espeurope.net>; Sun, 25 Dec 2016 21:47:27 +0100 (CET) Dec 25 21:49:08 ra-mx amavis[67599]: (67599-14) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T182139-67599-Iw5AO2Ei: <> -> <noreply@espeurope.net> SIZE=7152 Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <noreply@espeurope.net>; Sun, 25 Dec 2016 21:49:08 +0100 (CET) Dec 25 22:12:07 ra-mx amavis[69766]: (69766-05) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T202928-69766-zqjUPXL8: <notification+kr4keges24xr@facebookmail.com> -> <sto@kingkong.network> SIZE=12043 BODY=8BITMIME Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <sto@kingkong.network>; Sun, 25 Dec 2016 22:12:07 +0100 (CET) Dec 25 22:24:12 ra-mx amavis[67599]: (67599-15) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T182139-67599-Iw5AO2Ei: <kh004r5582@blueyonder.co.uk> -> <bounce@espeurope.net> SIZE=5022 Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <bounce@espeurope.net>; Sun, 25 Dec 2016 22:24:12 +0100 (CET) Dec 25 22:43:12 ra-mx amavis[69766]: (69766-06) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T202928-69766-zqjUPXL8: <> -> <noreply@espeurope.net> SIZE=7185 Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <noreply@espeurope.net>; Sun, 25 Dec 2016 22:43:12 +0100 (CET) Dec 25 23:35:30 ra-mx amavis[67599]: (67599-16) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T182139-67599-Iw5AO2Ei: <> -> <bounce@espeurope.net> SIZE=3752 BODY=8BITMIME ENVID=0OIR003T4IP20A10@etrn.telekom.sk Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <bounce@espeurope.net>; Sun, 25 Dec 2016 23:35:30 +0100 (CET) Dec 25 23:35:35 ra-mx amavis[69766]: (69766-07) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T202928-69766-zqjUPXL8: <> -> <bounce@espeurope.net> SIZE=3751 BODY=8BITMIME ENVID=0OIR003U4IP80A10@etrn.telekom.sk Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <bounce@espeurope.net>; Sun, 25 Dec 2016 23:35:35 +0100 (CET) Dec 25 23:37:53 ra-mx amavis[69766]: (69766-08) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T202928-69766-zqjUPXL8: <notification+kr4keges24xr@facebookmail.com> -> <sto@kingkong.network> SIZE=17322 BODY=8BITMIME Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <sto@kingkong.network>; Sun, 25 Dec 2016 23:37:53 +0100 (CET) Dec 25 23:39:12 ra-mx amavis[69766]: (69766-09) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T202928-69766-zqjUPXL8: <maja.wahlen@sunrise.ch> -> <bounce@espeurope.net> SIZE=7695 BODY=7BIT Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <bounce@espeurope.net>; Sun, 25 Dec 2016 23:39:12 +0100 (CET) Dec 25 23:44:23 ra-mx amavis[69766]: (69766-10) ESMTP [193.203.199.10]:10024 /var/amavis/tmp/amavis-20161225T202928-69766-zqjUPXL8: <> -> <noreply@espeurope.net> SIZE=7138 Received: from ra-mx.espeurope.net ([193.203.199.10]) by ra-mx (ra-mx.espeurope.net [193.203.199.10]) (amavisd-new, port 10024) with ESMTP for <noreply@espeurope.net>; Sun, 25 Dec 2016 23:44:23 +0100 (CET) '; my $regex = qr/(?<=Received: from ).*(?= by)/p; 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