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

/
/
gmx

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 = "^\\s*\n" + "# date\n" + "(?<date>\\d{4}-\\d{2}-\\d{2}\\s+\\d{2}:\\d{2}:\\d{2})\n" + "# facility.severity\n" + "\\s(?<facility>\\S+)\\.(?<severity>\\S+)\n" + "# server\n" + "\\s(?<server>\\S*)\n" + "# date\n" + "\\s(?<otherDate>\\d{4}-\\d{2}-\\d{2}:\\s\\d{2}:\\d{2}:\\d{2})\n" + "# time zone\n" + "\\s(?<timeZone>\\S*)\n" + "# ip address\n" + "\\s(?<ip>\\S*)\n" + "# legacy email address\n" + "\\s(?<legacyEmailAddress>\\S*)\n" + "# first name\n" + "\\s(?|\"(?<firstName>[^\"\\n]+)\"|(?<firstName>\\S*))\n" + "# last name\n" + "\\s(?|\"(?<lastName>[^\"\\n]+)\"|(?<lastName>\\S*))\n" + "# account number\n" + "\\s(?<account>\\S*)\n" + "# program code\n" + "\\s(?<programCode>\\S*)\n" + "# uid\n" + "\\s(?<uid>\\S*)\n" + "# email address\n" + "\\s(?<emailAddress>\\S*)\n" + "# event type\n" + "\\s(?<eventType>\\S*)\n" + "# source\n" + "\\s(?<source>\\S*)\n" + "# category\n" + "\\s(?<category>\\S*)\n" + "\\s*$"; final String string = "2016-01-29 18:19:54 local1.info server.domain.com 2016-01-29: 11:19:54 MST UNKNOWN UNKNOWN FOO \"BAR BAZ\" UNKNOWN UNKNOWN UNKNOWN EMAIL@EXAMPLE.COM PROFILE_CHANGE ProfileChangeProcessor A\n" + "2016-01-29 18:20:25 local4.info server.domain.com 2016-01-29: 11:20:25 MST UNKNOWN UNKNOWN \"F B\" BAZ ABC12345 GP SOME_UID EMAIL@EXAMPLE.COM EVENT_FROM_SOME_PROCESS UNKNOWN UNKNOWN\n" + "2016-01-29 18:23:10 local1.info server.domain.com 2016-01-29: 11:23:10 MST UNKNOWN UNKNOWN FOO BAR UNKNOWN UNKNOWN UNKNOWN EMAIL@EXAMPLE.COM SOME_CHANGE ProfileChangeProcessor AP\n" + "2016-01-29 18:26:24 local1.info server.domain.com 2016-01-29: 11:26:24 MST UNKNOWN EMAIL@EXAMPLE.COM FOO \"B'Baz\" UNKNOWN UNKNOWN UNKNOWN SOME_CHANGE ProfileChangeProcessor O\n" + "2016-01-29 18:26:55 local1.info server.domain.com 2016-01-29: 11:26:55 MST UNKNOWN EMAIL@EXAMPLE.COM \"FOO OR BAR\" BAZ SXR12646 GP UNKNOWN SOME_CHANGE ProfileChangeProcessor M"; 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