Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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

re = /failing[\w\W]*?\d*\)\s[\w\W]*?\:\n[\s\S]*?(Assert[\w\W]*?)[\n].*(src\/[^:]+):(\d+):(\d+)/ str = '   statement:propose  1) validates input   0 passing (1s)  1 failing  1) statement:propose validates input:  AssertionError: expected { Object (status, err) } to have a deep property \'err\' of \'err1\', but got \'Error while fetching the changes from the event store: {"error":"not_found","reason":"missing"}\' at doAsserterAsyncAndAddThen (node_modules/chai-as-promised/lib/chai-as-promised.js:307:16) at .<anonymous> (node_modules/chai-as-promised/lib/chai-as-promised.js:255:21) at ctx.(anonymous function) [as property] (node_modules/chai/lib/chai/utils/overwriteMethod.js:49:33) at Context.<anonymous> (src/aggregate/test/index.js:21:36) at Request.init (node_modules/request/request.js:191:10) at new Request (node_modules/request/request.js:130:8) at request (node_modules/request/index.js:54:10) at Future._computation (src/aggregate/index.js:375:7) at FutureNode$fork [as _f] (node_modules/fluture/fluture.js:910:10) at FutureMap$fork [as _f] (node_modules/fluture/fluture.js:1239:26) at FutureChain$fork$res (node_modules/fluture/fluture.js:1188:18) at FutureMap$fork$res (node_modules/fluture/fluture.js:1240:7) at FutureNode$fork$done (node_modules/fluture/fluture.js:912:22) at node_modules/level-sublevel/shell.js:102:12 at node_modules/level-sublevel/nut.js:122:19 at Immediate.callNext (node_modules/memdown/memdown.js:173:5) at MemDOWN._get (node_modules/memdown/memdown.js:172:3) at MemDOWN.AbstractLevelDOWN.get (node_modules/abstract-leveldown/abstract-leveldown.js:94:17) at Object.get (node_modules/level-sublevel/nut.js:117:28) at EventEmitter.emitter.get (node_modules/level-sublevel/shell.js:100:9) at Future._computation (src/aggregate/index.js:368:49) at FutureNode$fork [as _f] (node_modules/fluture/fluture.js:910:10) at FutureMap$fork [as _f] (node_modules/fluture/fluture.js:1239:26) at FutureChain$fork$res (node_modules/fluture/fluture.js:1188:18) at FutureOf$fork [as _f] (node_modules/fluture/fluture.js:871:5) at FutureChain$fork$res (node_modules/fluture/fluture.js:1188:18) at FutureOf$fork [as _f] (node_modules/fluture/fluture.js:871:5) at FutureChain$fork [as _f] (node_modules/fluture/fluture.js:1185:29) at FutureChain$fork [as _f] (node_modules/fluture/fluture.js:1185:29) at FutureChain$fork [as _f] (node_modules/fluture/fluture.js:1185:29) at FutureChain$fork [as _f] (node_modules/fluture/fluture.js:1185:29) at FutureChain$fork [as _f] (node_modules/fluture/fluture.js:1185:29) at FutureMap$fork [as _f] (node_modules/fluture/fluture.js:1239:26) at FutureMapRej$fork [as _f] (node_modules/fluture/fluture.js:1259:26) at Future$fork [as fork] (node_modules/fluture/fluture.js:252:17) at Seneca.<anonymous> (src/aggregate/index.js:205:10) at execute_action (node_modules/seneca/seneca.js:1092:20) at Object.act_fn [as fn] (node_modules/seneca/seneca.js:1042:11) at Immediate.processor (node_modules/gate-executor/gate-executor.js:136:14) at work_fn_callback (node_modules/gate-executor/gate-executor.js:195:7) at Seneca.reply (node_modules/seneca/seneca.js:1046:13) at src/aggregate/index.js:63:16 at FutureNode$fork$done (node_modules/fluture/fluture.js:912:22) at node_modules/level-sublevel/shell.js:53:51 at Immediate.<anonymous> (node_modules/level-sublevel/nut.js:109:13) at MemDOWN._batch (node_modules/memdown/memdown.js:208:3) at MemDOWN.AbstractLevelDOWN.batch (node_modules/abstract-leveldown/abstract-leveldown.js:189:17) at Object.apply (node_modules/level-sublevel/nut.js:87:23) at EventEmitter.emitter.put (node_modules/level-sublevel/shell.js:49:9) at Future._computation (src/aggregate/index.js:369:56) at FutureNode$fork [as _f] (node_modules/fluture/fluture.js:910:10) at FutureChainRej$fork$rej (node_modules/fluture/fluture.js:1219:18) at FutureNode$fork$done (node_modules/fluture/fluture.js:912:13) at node_modules/level-sublevel/shell.js:101:15 at node_modules/level-sublevel/nut.js:121:19 at Immediate.callNext (node_modules/memdown/memdown.js:166:47) at MemDOWN._get (node_modules/memdown/memdown.js:166:12) at MemDOWN.AbstractLevelDOWN.get (node_modules/abstract-leveldown/abstract-leveldown.js:94:17) at Object.get (node_modules/level-sublevel/nut.js:117:28) at EventEmitter.emitter.get (node_modules/level-sublevel/shell.js:100:9) at Future._computation (src/aggregate/index.js:368:49) at FutureNode$fork [as _f] (node_modules/fluture/fluture.js:910:10) at FutureChain$fork$res (node_modules/fluture/fluture.js:1188:18) at FutureOf$fork [as _f] (node_modules/fluture/fluture.js:871:5) at FutureChain$fork [as _f] (node_modules/fluture/fluture.js:1185:29) at FutureChainRej$fork [as _f] (node_modules/fluture/fluture.js:1216:29) at Future$fork [as fork] (node_modules/fluture/fluture.js:252:17) at Seneca.<anonymous> (src/aggregate/index.js:61:8) at execute_action (node_modules/seneca/seneca.js:1092:20) at Object.act_fn [as fn] (node_modules/seneca/seneca.js:1042:11) at processor (node_modules/gate-executor/gate-executor.js:136:14) at Immediate.<anonymous> (node_modules/gate-executor/gate-executor.js:240:7) at GateExecutor.self.start (node_modules/gate-executor/gate-executor.js:233:5) at Object.gate [as fn] (node_modules/gate-executor/gate-executor.js:329:10) at Immediate.processor (node_modules/gate-executor/gate-executor.js:136:14) at work_fn_callback (node_modules/gate-executor/gate-executor.js:195:7) at work_fn_callback (node_modules/gate-executor/gate-executor.js:186:11) at Seneca.reply (node_modules/seneca/seneca.js:1046:13) at Seneca.<anonymous> (src/state/index.js:49:12) at execute_action (node_modules/seneca/seneca.js:1092:20) at Object.act_fn [as fn] (node_modules/seneca/seneca.js:1042:11) at processor (node_modules/gate-executor/gate-executor.js:136:14) at Immediate.<anonymous> (node_modules/gate-executor/gate-executor.js:240:7) at GateExecutor.self.start (node_modules/gate-executor/gate-executor.js:233:5) at Object.gate [as fn] (node_modules/gate-executor/gate-executor.js:329:10) at Immediate.processor (node_modules/gate-executor/gate-executor.js:136:14) at work_fn_callback (node_modules/gate-executor/gate-executor.js:195:7) at work_fn_callback (node_modules/gate-executor/gate-executor.js:186:11) at Seneca.reply (node_modules/seneca/seneca.js:1046:13) at handle_inward_break (node_modules/seneca/seneca.js:1211:13) at execute_action (node_modules/seneca/seneca.js:1082:11) at Object.act_fn [as fn] (node_modules/seneca/seneca.js:1042:11) at processor (node_modules/gate-executor/gate-executor.js:136:14) at Immediate.<anonymous> (node_modules/gate-executor/gate-executor.js:240:7) at GateExecutor.self.start (node_modules/gate-executor/gate-executor.js:233:5) at Object.gate [as fn] (node_modules/gate-executor/gate-executor.js:329:10) at processor (node_modules/gate-executor/gate-executor.js:136:14) at Immediate.<anonymous> (node_modules/gate-executor/gate-executor.js:240:7) at GateExecutor.self.start (node_modules/gate-executor/gate-executor.js:233:5) at make_seneca (node_modules/seneca/seneca.js:507:6) at init (node_modules/seneca/seneca.js:224:16) at Object.<anonymous> (test/unit/helper.js:28:17) at loader (node_modules/babel-register/lib/node.js:144:5) at Object.require.extensions.(anonymous function) [as .js] (node_modules/babel-register/lib/node.js:154:7) at require (internal/module.js:20:19) at Array.forEach (native) at run (bootstrap_node.js:394:7) at startup (bootstrap_node.js:149:9) at bootstrap_node.js:509:3  (node:11964) Warning: a promise was created in a handler at Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb-replicator/lib/index.js:87:24 but was not returned from it, see http://goo.gl/rRqMUw at new Promise (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/bluebird/js/release/promise.js:79:10) (node:11964) Warning: a promise was created in a handler at Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/express-pouchdb/lib/daemon-manager.js:28:16 but was not returned from it, see http://goo.gl/rRqMUw at Function.Promise.cast (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/bluebird/js/release/promise.js:196:13) (node:11964) Warning: a promise was created in a handler at Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/express-pouchdb/lib/daemon-manager.js:28:16 but was not returned from it, see http://goo.gl/rRqMUw at new Promise (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/bluebird/js/release/promise.js:79:10) (node:11964) Warning: a promise was rejected with a non-error: [object String] (node:11964) Warning: a promise was created in a handler at Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/express-pouchdb/lib/routes/authentication.js:96:7 but was not returned from it, see http://goo.gl/rRqMUw at new Promise (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/bluebird/js/release/promise.js:79:10) Unhandled rejection {"status":404,"name":"not_found","message":"missing","reason":"missing"} (No stack trace) From previous event: at PouchDB$5.<anonymous> (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:117:19) at PouchDB$5.get (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/argsarray/index.js:14:18) at PouchDB$5.<anonymous> (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb-wrappers/index.js:155:18) at securityWrapper (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb-security/lib/index.js:55:12) at callHandlers (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb-wrappers/index.js:447:17) at PouchDB$5.get (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb-wrappers/index.js:154:12) at Object.filter (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:3849:26) at Changes$2.doChanges (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:1638:45) at /Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:1598:12 at Object.validate (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:3786:3) at Changes$2.validateChanges (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:1594:36) at /Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:1551:14 at TaskQueue$1.execute (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:2580:7) at TaskQueue$1.ready (/Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:2593:8) at /Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:2740:20 at /Users/jun/dev/OII/current/oi/code/aggregates/statement/node_modules/pouchdb/lib/index.js:4913:15 at _combinedTickCallback (internal/process/next_tick.js:67:7) at process._tickCallback (internal/process/next_tick.js:98:9) Error while loading the aggregate state Error while fetching the changes from the event store: {"error":"not_found","reason":"missing"} ' # Print the match result str.scan(re) do |match| puts match.to_s end

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 Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html