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

/
/
gm

Test String

Substitution

Processing...

Code Generator

Generated Code

# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression. sed -E 's/(\(\)\n[[:space:]]{1,}\{)|(\(\)[[:space:]]{1,}\{)/()\n {\n clearScreen();/gm;t' <<< "// feedback thread import java.util.*; class Main { static Scanner scan = new Scanner(System.in); static String deadEnd = \"dead end--morphing backwards!\"; static String gettingCloser = \"You'r getting closer\"; // call this method after each decision has been made public static void clearScreen() { Scanner scan = new Scanner(System.in); System.out.println(\"Press enter to continue.\"); String x = scan.nextLine(); System.out.print(\"\033[H\033[2J\"); System.out.flush(); } public static void decisionZero() { System.out.println(\"Decision Point 0\"); System.out.println(\"Choose a direction Mr. Mouse\"); String direction = scan.nextLine(); switch (direction.toLowerCase()) { case \"n\": System.out.println(\"You chose north.\"); System.out.println(deadEnd); decisionZero(); break; case \"s\": System.out.println(\"You chose south.\"); System.out.println(gettingCloser); decisionOne(); break; case \"e\": System.out.println(\"You chose east.\"); System.out.println(deadEnd); decisionZero(); break; case \"w\": System.out.println(\"You chose west.\"); System.out.println(deadEnd); decisionZero(); break; } } public static void decisionOne() { System.out.println(\"Decision Point 1\"); System.out.println(\"Choose a direction Mr. Mouse\"); String direction = scan.nextLine(); switch (direction.toLowerCase()) { case \"n\": System.out.println(\"You chose north.\"); System.out.println(deadEnd); decisionZero(); break; case \"s\": System.out.println(\"You chose south.\"); System.out.println(deadEnd); decisionZero(); break; case \"e\": System.out.println(\"You chose east.\"); System.out.println(deadEnd); decisionZero(); break; case \"w\": System.out.println(\"You chose west.\"); System.out.println(gettingCloser); decisionTwo(); break; } } public static void decisionTwo() { System.out.println(\"Decision Point 2\"); System.out.println(\"Choose a direction Mr. Mouse\"); String direction = scan.nextLine(); int rndDecion = (int)(Math.random()*2); switch (direction.toLowerCase()) { case \"n\": System.out.println(\"You chose north.\"); System.out.println(gettingCloser); decisionThree(); break; case \"s\": System.out.println(\"You chose south.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); } break; case \"e\": System.out.println(\"You chose east.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); } break; case \"w\": System.out.println(\"You chose west.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); } break; } } public static void decisionThree() { System.out.println(\"Decision Point 3\"); System.out.println(\"Choose a direction Mr. Mouse\"); String direction = scan.nextLine(); int rndDecion = (int)(Math.random()*3); switch (direction.toLowerCase()) { case \"n\": System.out.println(\"You chose north.\"); System.out.println(gettingCloser); decisionFour(); break; case \"s\": System.out.println(\"You chose south.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); } break; case \"e\": System.out.println(\"You chose east.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); } break; case \"w\": System.out.println(\"You chose west.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); } break; } } public static void decisionFour() { System.out.println(\"Decision Point 4\"); System.out.println(\"Choose a direction Mr. Mouse\"); String direction = scan.nextLine(); int rndDecion = (int)(Math.random()*4); switch (direction.toLowerCase()) { case \"n\": System.out.println(\"You chose north.\"); System.out.println(gettingCloser); decisionFive(); break; case \"s\": System.out.println(\"You chose south.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); } break; case \"e\": System.out.println(\"You chose east.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); } break; case \"w\": System.out.println(\"You chose west.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); } break; } } public static void decisionFive() { System.out.println(\"Decision Point 5\"); System.out.println(\"Choose a direction Mr. Mouse\"); String direction = scan.nextLine(); int rndDecion = (int)(Math.random()*5); switch (direction.toLowerCase()) { case \"n\": System.out.println(\"You chose north.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); case 4: decisionFour(); } break; case \"s\": System.out.println(\"You chose south.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); case 4: decisionFour(); } break; case \"e\": System.out.println(\"You chose east.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); case 4: decisionFour(); } break; case \"w\": System.out.println(\"You chose west.\"); System.out.println(gettingCloser); decisionSix(); break; } } public static void decisionSix() { System.out.println(\"Decision Point 6\"); System.out.println(\"Choose a direction Mr. Mouse\"); String direction = scan.nextLine(); int rndDecion = (int)(Math.random()*5); switch (direction.toLowerCase()) { case \"n\": System.out.println(\"You chose north.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); case 4: decisionFour(); } break; case \"s\": System.out.println(\"You chose south.\"); System.out.println(deadEnd); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); case 4: decisionFour(); } break; case \"e\": System.out.println(\"You chose east.\"); System.out.println(\"Victory cheese!\"); break; case \"w\": System.out.println(\"You chose west.\"); System.out.println(gettingCloser); switch (rndDecion) { case 0: decisionZero(); case 1: decisionOne(); case 2: decisionTwo(); case 3: decisionThree(); case 4: decisionFour(); } break; } } // the main method is COMPLETE. Add/change nothing here. public static void main(String[] args) { decisionZero(); //only line in main method. } }"

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 SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html