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

Substitution

Processing...

Code Generator

Language

Generated Code

# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression. sed -E 's/(?<=\s)((?:docstring|some_detailed_notes)\s*=\s*\(?\s*(?:\/\/.*\n\s*)*)"((?:[^"\\]|\\.)+)"(\s*\)?\s*;)/\1R""""\2""""\3/gm;t' <<< "class myClassA(myBaseClass) { docstring = // End-of-line-comments possible \" This is my class description docstring stored in a string variable inherited from myBaseClass. The content of this string, INCLUDING INDENTATION, MUST NOT be changed. \"; docstring = ( \" Enclosed in parentheses \" ); // This variable is declared as string has a mismatched indentation: string some_detailed_notes = \"Some string like this is also possible. Also with some really strange indentation and `inline code`, ```code blocks``` $\\text{LaTeX}$ $$\\frac{1}{2}$$ :::{hint} some admonitions ::: and all kind of special characters such as: \\" (...) {...} [...] ;., etc. which MUST be preserved.\"; string some_other_string = \" do NOT touch this, only docstring and some_detailed_notes \"; }"

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 SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html