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 (6)

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

r"
"
g

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

// include the latest version of the regex crate in your Cargo.toml extern crate regex; use regex::Regex; fn main() { let regex = Regex::new(r#"(\n|;|^)"([^";\n]*?)"([^";\n]+?)"([^";\n]*?)"(\n|;|$)"#).unwrap(); let string = "A stable and simple RegEx, which escapes double-quotes (\") in a CSV file. ## Tests ## \"Great thing?!*\";\"I love RegEx!\";\"And especially \"regex101.com\"!\";\"Just amazing...\" \"Something090324*?!*\";\"Somethi\"ng090\"324*?!*\";\"Something090324*?!*\";\"Something090324*?!*\" Ignore\"THIS\"ItIsNotARealQuote?!*;\"This\"is\"real!\";HereIsNoQuoteSymbolAtAll;This\"IsOnlyOneQuoteSymbol CSV: Escape double-quotes (\") in quoted ## Issues ## - Does not support embedded line breaks, but you can easily modify it to support them. Note that they are currently forbitten to be more stable. - Does only allow \" for quoting. (Replace it in the whole RegEx to change this) - Only works with ; as a separator. (Replace it in the whole RegEx to change this) - Does not allow separator character inside of quotes string. Look at the following example: \"Example \"string\"\";\"works\" \"Example \"string\";\";\"fails\" - Get's problems when the issue happens \"too often\", which means it shows up in cells which are directly side-by-side. You may work around this issue by running it multiple times: \"run 1 time \";\"a string with a \"small\" issue\";\"and \"another\" one\" \"run 2 times\";\"a string with a \"\"small\"\" issue\";\"and \"another\" one\" - It only works with quoted strings (no single \" are escaped; only double ones) ## Changelog ## v1.0 - 2016-01-25 - released Author: rugk <rugk@posteo.de>"; let substitution = "\\1\"\\2\"\"\\3\"\"\\4\"\\5"; // result will be a String with the substituted value let result = regex.replace_all(string, substitution); println!("{}", result); }

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 Rust, please visit: https://docs.rs/regex/latest/regex/