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"
"
gm

Test String

Code Generator

Language

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"^[a-z_][a-z0-9_-]{0,30}[a-z0-9_$-]?:[^:]*:\d+:\d+:[^:]*:[^:]*:[^:]*$"; string input = @"root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin mail:x:8:8:mail:/var/mail:/usr/sbin/nologin news:x:9:9:news:/var/spool/news:/usr/sbin/nologin uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin proxy:x:13:13:proxy:/bin:/usr/sbin/nologin www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin backup:x:34:34:backup:/var/backups:/usr/sbin/nologin list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin mysql:x:115:124:MySQL Server,,,:/var/lib/mysql:/bin/false sshd:x:116:65534::/var/run/sshd:/usr/sbin/nologin guest:x:118:125:Guest,,,:/tmp/guest-home.phc17z:/bin/bash gordon:x:1004:1000:Assaf Gordon,,,,:/home/gordon:/bin/bash charles:x:1005:1000:Charles,,,,:/home/charles:/bin/bash alice:x:1006:1000:Alice,,,,:/home/alice:/bin/bash bob:x:1007:1000:Bob,,,,:/home/bob:/bin/bash postgres:x:119:126:PostgreSQL administrator,,,:/var/lib/postgresql:/bin/bash rabbitmq:x:125:138:RabbitMQ messaging server,,,:/var/lib/rabbitmq:/bin/false redis:x:126:140:redis server,,,:/var/lib/redis:/bin/false postfix:x:127:141::/var/spool/postfix:/bin/false root::0:0:root:/root:/bin/sh bin:*:1:1:bin:/bin:/bin/false daemon:*:2:2:daemon:/sbin:/bin/false adm:*:3:4:adm:/var/account:/bin/false lp:*:4:7:lp:/var/spool/lpd:/bin/false sync:*:5:0:sync:/sbin:/bin/sync shutdown:*:6:0:shutdown:/sbin:/sbin/shutdown halt:*:7:0:halt:/sbin:/sbin/halt mail:*:8:12:mail:/var/mail:/bin/false news:*:9:13:news:/home/services/news:/bin/false uucp:*:10:14:uucp:/var/spool/uucp:/bin/false operator:*:11:0:operator:/root:/bin/false games:*:12:20:games:/usr/games:/bin/false ftp:*:14:50:FTP User:/home/services/ftp:/bin/false http:*:51:51:HTTP User:/home/services/httpd:/bin/false stats:*:123:123:Statistics generator user:/usr/share/empty:/bin/false nobody:*:99:99:Nobody:/usr/share/empty:/bin/false root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin adm:x:3:4:adm:/var/adm:/sbin/nologin lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin sync:x:5:0:sync:/sbin:/bin/sync shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown halt:x:7:0:halt:/sbin:/sbin/halt mail:x:8:12:mail:/var/spool/mail:/sbin/nologin news:x:9:13:news:/etc/news: uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin operator:x:11:0:operator:/root:/sbin/nologin games:x:12:100:games:/usr/games:/sbin/nologin gopher:x:13:30:gopher:/var/gopher:/sbin/nologin ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin nobody:x:99:99:Nobody:/:/sbin/nologin nscd:x:28:28:NSCD Daemon:/:/sbin/nologin vcsa:x:69:69:virtual console memory owner:/dev:/sbin/nologin pcap:x:77:77::/var/arpwatch:/sbin/nologin ntp:x:38:38::/etc/ntp:/sbin/nologin dbus:x:81:81:System message bus:/:/sbin/nologin avahi:x:70:70:Avahi daemon:/:/sbin/nologin rpc:x:32:32:Portmapper RPC user:/:/sbin/nologin apache:x:48:48:Apache:/var/www:/sbin/nologin mailnull:x:47:47::/var/spool/mqueue:/sbin/nologin smmsp:x:51:51::/var/spool/mqueue:/sbin/nologin hsqldb:x:96:96::/var/lib/hsqldb:/sbin/nologin sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin xfs:x:43:43:X Font Server:/etc/X11/fs:/sbin/nologin haldaemon:x:68:68:HAL daemon:/:/sbin/nologin avahi-autoipd:x:100:102:avahi-autoipd:/var/lib/avahi-autoipd:/sbin/nologin gdm:x:42:42::/var/gdm:/sbin/nologin jackhuang:x:501:501::/home/jackhuang:/bin/bash mysql:x:27:27:MySQL Server:/var/lib/mysql:/bin/bash roye:x:502:502::/home/roye:/bin/bash ecnet:x:503:503::/var/www/html:/bin/bash phoebe:x:504:504::/home/phoebe:/bin/bash"; RegexOptions options = RegexOptions.Multiline; foreach (Match m in Regex.Matches(input, pattern, options)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

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 C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx