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

/
/
gm

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 = "<!--\\s*ID\\:\\s*\\d+\\s*-->(?=\\n*-\\s+)"; final String string = "### Alias\n\n" + "Q: what check to do before creating an alias?\n\n" + "A: check whether any other command exists by that name using `type new-alias-name`\n" + "<!--ID: 1643091253375-->\n\n" + "---\n\n" + "Q: syntax to create an alias?\n\n" + "A: `alias name='string'`\n" + "<!--ID: 1645446702965-->\n\n" + "- no spaces before or after the equal sign\n" + "- single quotes around the command sequence\n" + "![[Pasted image 20220125092954.png]]\n" + "<!--ID: 1643091253408-->\n\n" + "---\n\n" + "### Redirection/Piping\n\n" + "Q: output of `> ls-output.txt`\n\n" + "A: the file will be truncated if it exists or it would be created.\n" + "<!--ID: 1645087988730-->\n\n" + "- Simply using the redirection operator with no command preceding it will truncate an existing file or create a new empty file\n" + "<!--ID: 1643351731943-->\n\n"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); 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