Regular Expressions 101

Save & Share

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

/
/
gms

Test String

Substitution

Processing...

Code Generator

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(?x)\n" + ".+(?:Sub|Function)\\ (\\w+)\\( # method declaration\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n" + "(?: # start of parameter pattern\n" + "[\\w\\W]*?(?<=\\b) # parameter may be preceded by ByVal or Optional keywords\n" + "([a-z]\\w+)+ # parameter starts with a lower case\n" + ".*? # parameter may be followed by its type declaration\n" + "(?:=\\ ([^\\,]+)){0,1} # optional parameters may be followed by default value, it is captured to be used in method call\n" + "(?:,|\\)) # parameter is followed by , or )\n" + "){0,1} # end of parameter pattern (may be copy-pasted infinitely to capture all parameters)\n"; final String string = "Public Function BrowseToDictTreeNode(ByVal rootNode As Scripting.Dictionary, ByVal browseKey As String, ByVal nodeUrl As String, _\n" + " Optional ByVal urlSlash As String = \"/\", Optional ByVal childrenKey As String = \"Children\", _\n" + " Optional ByVal startAtLevel As Integer = 1) As Scripting.Dictionary\n"; final String subst = "#Sub call\\n$1 $2:=$3, $4:=$5, $6:=$7, $8:=$9, $10:=$11, $12:=$13, $14:=$15, $16:=$17, $18:=$19, $20:=$21, $20:=$21, $22:=$23, $24:=$25\\n\\n#Function call\\n$1($2:=$3, $4:=$5, $6:=$7, $8:=$9, $10:=$11, $12:=$13, $14:=$15, $16:=$17, $18:=$19, $20:=$21, $20:=$21, $22:=$23, $24:=$25)\\n\\n#Recursive Sub call\\n$1 $2:=$2, $4:=$4, $6:=$6, $8:=$8, $10:=$10, $12:=$12, $14:=$14, $16:=$16, $18:=$18, $20:=$20, $22:=$22, $24:=$24, \\n\\n#Recursive Function call\\n$1($2:=$2, $4:=$4, $6:=$6, $8:=$8, $10:=$10, $12:=$12, $14:=$14, $16:=$16, $18:=$18, $20:=$20, $22:=$22, $24:=$24, )"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.DOTALL); final Matcher matcher = pattern.matcher(string); // The substituted value will be contained in the result variable final String result = matcher.replaceAll(subst); System.out.println("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 Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html