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

/
/
mxg

Test String

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 = "\n" + " (?:\\n|\\A)[ ]*\n" + " # 1: Opening marker\n" + " (\n" + " [ ]{0,2}(?:~{3,}|`{3,}) # 3 or more tildes/backticks.\n" + " )\n" + " [ ]*\n" + " (?:\n" + " \\.?([\\w-_:\\.\\/\\{\\+\\},\\@]+) # 2: standalone class name\n" + " |\n" + " \\{((?:[ ]*[#.][-_:a-zA-Z0-9]+){1,})[ ]*\\} # 3: Extra attributes\n" + " )?\n" + " [ ]* \\n # Whitespace and newline following marker.\n" + " \n" + " # 4: Content\n" + " (\n" + " (?>\n" + " (?!\\1 [ ]* \\n) # Not a closing marker.\n" + " .*\\n+\n" + " )+\n" + " )\n" + " \n" + " # Closing marker.\n" + " \\1 [ ]* (?= \\n )"; final String string = "\n\n" + "B1B\n\n\n\n" + "{{ site.data.reusables.ssh.dsa-support }}\n\n" + "{{ site.data.reusables.command_line.open_the_multi_os_terminal }}\n\n" + "2. Enter `ls -al ~/.ssh` to see if existing SSH keys are present:\n\n" + "```shell\n" + " $ ls -al ~/.ssh\n" + " # Lists the files in your .ssh directory, if they exist\n" + "```\n" + "dadas\n" + "dasdasdasda\n\n" + " ~~~dadasd\n" + "$ ls -al ~/.ssh\n" + "# Lists the files in your .ssh directory, if they exist\n" + " ~~~\n" + "3. Check the directory listing to see if you already have a public SSH key.\n\n" + "By default, the filenames of the public keys are one of the following:\n\n" + "* *id_dsa.pub*\n" + "* *id_ecdsa.pub*\n" + "* *id_ed25519.pub*\n" + "* *id_rsa.pub*\n\n" + "- If you don't have an existing public and private key pair, or don't wish to use any that are available to connect to GitHub, then [generate a new SSH key](/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent).\n" + "- If you see an existing public and private key pair listed (for example *id_rsa.pub* and *id_rsa*) that you would like to use to connect to GitHub, you can [add your SSH key to the ssh-agent](/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent/#adding-your-ssh-key-to-the-ssh-agent).\n\n" + "{{#tip}}\n\n" + "**Tip:** If you receive an error that *~/.ssh* doesn't exist, don't worry! We'll create it when we [generate a new SSH key](/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent).\n\n" + "{{/tip}}"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.COMMENTS); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

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