Regular Expressions 101

Save & Share

  • Regex Version: ver. 4
  • Update Regex
    ctrl+⇧+s
  • Save new Regex
    ctrl+s
  • Add to Community Library

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /\$([^{("\\'\/])([a-zA-Z0-9_]*)([^}\/ \t'"\n.\]:]*)/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('\\$([^{("\\\\\'\\\/])([a-zA-Z0-9_]*)([^}\\\/ \\t\'"\\n.\\]:]*)', 'gm') const str = `#!/usr/bin/env bash # version 0.1.0 function generate_secret() { ( umask 0077 ; dd if=/dev/urandom bs=24 count=1 2>/dev/null | base64 -w0 > "\$1" ) } if [[ -n \$SRS_DOMAINNAME ]] then NEW_DOMAIN_NAME="\$SRS_DOMAINNAME" elif [[ -n \$OVERRIDE_HOSTNAME ]] then NEW_DOMAIN_NAME="\${OVERRIDE_HOSTNAME#*.}" elif [[ -n \$DOMAINNAME ]] then NEW_DOMAIN_NAME="\$DOMAINNAME" else NEW_DOMAIN_NAME=\$(hostname -d) fi sed -i -e "s/localdomain/\${NEW_DOMAIN_NAME}/g" /etc/default/postsrsd POSTSRSD_SECRET_FILE='/etc/postsrsd.secret' POSTSRSD_STATE_DIR='/var/mail-state/etc-postsrsd' POSTSRSD_STATE_SECRET_FILE="\${POSTSRSD_STATE_DIR}/postsrsd.secret" if [[ -n \$SRS_SECRET ]] then ( umask 0077 ; echo "\$SRS_SECRET" | tr ',' '\\n' > "\$POSTSRSD_SECRET_FILE" ) else if [[ \$ONE_DIR -eq 1 ]] then if [[ ! -f \$POSTSRSD_STATE_SECRET_FILE ]] then install -d -m 0775 "\$POSTSRSD_STATE_DIR" generate_secret "\$POSTSRSD_STATE_SECRET_FILE" fi install -m 0400 "\$POSTSRSD_STATE_SECRET_FILE" "\$POSTSRSD_SECRET_FILE" elif [[ ! -f \$POSTSRSD_SECRET_FILE ]] then generate_secret "\$POSTSRSD_SECRET_FILE" fi fi if [[ -n \$SRS_EXCLUDE_DOMAINS ]] then sed -i -e "s/^#\\?SRS_EXCLUDE_DOMAINS=.*\$/SRS_EXCLUDE_DOMAINS=\$SRS_EXCLUDE_DOMAINS/g" /etc/default/postsrsd fi /etc/init.d/postsrsd start `; const subst = `${$1$2$3}`; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

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 JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions