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

`
`
gm

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)(HEALTHCHECK)(((?:\s*\\?\s*)--\w+=\w+(?:\s*\\?\s*))*)`) var str = `FROM golang as build RUN apt-get install wget curl && \ wget https://github.com/watchexec/watchexec/releases/download/v1.24.2/watchexec-1.24.2-x86_64-unknown-linux-gnu.deb && \ dpkg -i watchexec-1.24.2-x86_64-unknown-linux-gnu.deb && \ rm watchexec-1.24.2-x86_64-unknown-linux-gnu.deb ENV REPOSITORY_ROOT="/repositories" ENV TEMPLATE_DIR="/api/templates" ENV STATIC_DIR="/api/static" WORKDIR /api/src RUN mkdir /.cache && chmod 0777 /.cache HEALTHCHECK --interval=10s --timeout=10s --retries=3 CMD curl http://localhost:3333/sign-in USER 1234:1234 ENTRYPOINT ["watchexec", "-r", "-w", "/api", "go", "run", "."]` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", 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 Golang, please visit: https://golang.org/pkg/regexp/