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
No Match

r"
"
xs

Test String

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = " ^(?P<timestamp>\\d{4}/\\d{2}/\\d{2}\\ \\d{2}:\\d{2}:\\d{2})\n" + " \\ \\[(?P<severity>emerg|alert|crit|error|warn|notice|info)\\]\n" + " \\ (?P<process_id>\\d+)\n" + " \\#(?P<thread_id>\\d+):\n" + " \\ \\*(?P<connection_id>\\d+)\n" + " \\ (?P<error>.+?)\n" + " (?:\\ while\\ (?P<context>.+?))?\n" + " ,\\ client:\\ (?P<client_ip>\\d+\\.\\d+\\.\\d+\\.\\d+)\n" + " ,\\ server:\\ (?P<server>.+?)\n" + " (?:,\\ request:\\ \\\"(?P<request_method>[A-Z]+?)\n" + " \\ (?P<request_path>\\/.+?)\n" + " \\ (?P<request_protocol>.+?)\\\")?\n" + " (?:,\\ upstream:\\ \\\"(?P<upstream>.+?)\\\")?\n" + " (?:,\\ host:\\ \\\"(?P<host>.+?)\\\")?\n" + " (?:,\\ referrer:\\ \\\"(?P<referrer>.+?)\\\")?\n" + " $"; final String string = "2019/07/11 07:19:30 [error] 934#934: *18897816 open() \"/local/nginx/static/ads.txt\" failed (2: No such file or directory), client: 85.195.82.90, server: app.digitale-sammlungen.de, request: \"GET /ads.txt HTTP/1.1\", host: \"app.digitale-sammlungen.de\""; final Pattern pattern = Pattern.compile(regex, Pattern.COMMENTS | Pattern.DOTALL); final Matcher matcher = pattern.matcher(string); if (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