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

/
/
g

Test String

Code Generator

Language

Generated Code

# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r"(?:rd|ed|USER=|disconnected by|closed)\s?(?:for)?\s?(?:invalid\suser\s)?(?<user>\w+)" test_str = ("Sat Jun 03 2017 22:53:03 cisco_router1 sshd[4926]: Failed password for invalid user info from 2.229.4.58 port 4509 ssh2\n" "Sat Jun 03 2017 22:55:37 cisco_router1 sshd[3720]: Failed password for peevish from 2.229.4.58 port 1299 ssh2\n\n" "Sat Jun 03 2017 22:54:09 cisco_router1 sshd[15833]: pam_unix(sshd:session): session opened for user nsharpe by (uid=0)\n\n" "Tue Jul 04 2017 16:59:10 cisco_router1 sshd[64913]: pam_unix(sshd:session): session closed for user nsharpe by (uid=0)\n\n" "Tue Jul 04 2017 14:21:40 cisco_router1 su: pam_unix(su:session): session closed for user root\n\n" "Sat Jun 03 2017 22:55:13 cisco_router1 sshd[1952]: Accepted password for djohnson from 10.3.10.46 port 1182 ssh2\n\n" "Sat Jun 03 2017 22:55:37 cisco_router1 sudo: myuan ; TTY=pts/0 ; PWD=/home/myuan ; USER=root ; COMMAND=/bin/su\n\n" "Tue Jul 04 2017 16:59:10 cisco_router1 sshd[59602]: Received disconnect from 10.2.10.163 11: disconnected by user\n\n\n" "Tue Jul 04 2017 16:59:10 cisco_router1 sshd[59602]: Received disconnect from 10.2.10.163 11: disconnected by user\n\n\n\n") matches = re.finditer(regex, test_str) for matchNum, match in enumerate(matches, start=1): print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group())) for groupNum in range(0, len(match.groups())): groupNum = groupNum + 1 print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum))) # Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.

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 Python, please visit: https://docs.python.org/3/library/re.html