Regular Expressions 101

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  • Unit Tests (9)

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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>.{19})\\ \\[(?P<severity>\\w{4,6})\\]\n" + "\\ \\d+\\#\\d+:\\ (\\*\\d+\\ )?\n" + "(?P<err_msg>\n" + " (?:\\\"\\S+\\\"\\sis\\snot\\s)?\n" + " (?P<err_type>\\w+)[\\s(] \n" + " (?:requests,\\ excess:\\ (?P<err_rate>\\d+\\.\\d+)\n" + " \\ by\\ zone\\ \\\"(?P<err_zone>\\S+)\\\"\n" + " |.+?)\n" + ")\n" + "(?:\n" + " ,\\ client:\\ (?P<remote_addr>\\d+\\.\\d+\\.\\d+\\.\\d+)\n" + " ,\\ server:\\ (?P<server>[^,\\a]+)\n" + " (?:,\\ request:\\ \\\"(?P<method>[A-Z]{3,4}?)\n" + " \\ (?P<uri>\\/\\S*?)(?P<uri_query>\\?\\S+)?\n" + " \\ (?P<protocol>\\S+)\\\"\n" + " )?\n" + " (?:,\\ upstream:\\ \\\"(?P<upstream>.+?)\\\")?\n" + " (?:,\\ host:\\ \\\"(?P<req_host>\\S+)\\\")?\n" + " (?:,\\ referrer:\\ \\\"(?P<referrer>\\S+)\\\")?\n" + "|)\n" + "$"; final String string = "2023/06/16 17:12:30 [error] 1814859#1814859: *228570402 limiting requests, excess: 50.120 by zone \"resizerzone\", client: 10.5.0.122, server: app.market.com, request: \"GET /resizer/view?key=8e158c8741ce849a09ef84d316bb68e7&b=productimages&f=webp&s=0 HTTP/1.1\", host: \"market.com\", referrer: \"https://market.com/\"\n"; 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