regex101: PCRE (Legacy) Match Workspace

Pro

Negative Lookbehind(?<!\\)

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

Comment: negative look-behind to make sure start is not escaped

Non-Capturing Group(?: # start non-capture group for all possible match starts # group 1, match dollar signs only # single or double dollar sign enforced by look-arounds ((?<!\$)\${1,2}(?!\$))| # group 2, match escaped parenthesis (\\\()| # group 3, match escaped bracket (\\\[)| # group 4, match begin equation (\\begin\{equation\}) )

1st Alternative # start non-capture group for all possible match starts # group 1, match dollar signs only # single or double dollar sign enforced by look-arounds ((?<!\$)\${1,2}(?!\$))

Comment: start non-capture group for all possible match starts

Comment: group 1, match dollar signs only

Comment: single or double dollar sign enforced by look-arounds

Group 1((?<!\$)\${1,2}(?!\$))

Negative Lookbehind(?<!\$)

\$the literal $ (36₁₀ / 44₈ / 24₁₆)

\${1,2}the literal $ (36₁₀ / 44₈ / 24₁₆) , repeated between 1 and 2 times

Negative Lookahead(?!\$)

\$the literal $ (36₁₀ / 44₈ / 24₁₆)

2nd Alternative # group 2, match escaped parenthesis (\\\()

Comment: group 2, match escaped parenthesis

Group 2(\\\()

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

\(the literal ( (40₁₀ / 50₈ / 28₁₆)

3rd Alternative # group 3, match escaped bracket (\\\[)

Comment: group 3, match escaped bracket

Group 3(\\\[)

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

4th Alternative # group 4, match begin equation (\\begin\{equation\})

Comment: group 4, match begin equation

Group 4(\\begin\{equation\})

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

beginthe literal text begin (case sensitive)

\{the literal { (123₁₀ / 173₈ / 7B₁₆)

equationthe literal text equation (case sensitive)

\}the literal } (125₁₀ / 175₈ / 7D₁₆)

Comment: if group 1 was start

Condition(?(1) # non greedy match everything in between # group 1 matches do not support recursion (.*?)(?<!\\) # match ending double or single dollar signs (?<!\$)\1(?!\$)| # else (?: # greedily and recursively match everything in between # groups 2, 3 and 4 support recursion (.*(?R)?.*)(?<!\\) (?: # if group 2 was start, escaped parenthesis is end (?(2)\\\)| # if group 3 was start, escaped bracket is end (?(3)\\\]| # else group 4 was start, match end equation \\end\{equation\} ) ))))

Uses the first branch if group 1 matched

If the condition is true, match this branch: # non greedy match everything in between # group 1 matches do not support recursion (.*?)(?<!\\) # match ending double or single dollar signs (?<!\$)\1(?!\$)

Comment: non greedy match everything in between

Comment: group 1 matches do not support recursion

Group 5(.*?)

.*?any character (except for line terminators), repeated any number of times

Negative Lookbehind(?<!\\)

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

Comment: match ending double or single dollar signs

Negative Lookbehind(?<!\$)

\$the literal $ (36₁₀ / 44₈ / 24₁₆)

\1the text saved by group 1

Negative Lookahead(?!\$)

\$the literal $ (36₁₀ / 44₈ / 24₁₆)

Otherwise, match this branch: # else (?: # greedily and recursively match everything in between # groups 2, 3 and 4 support recursion (.*(?R)?.*)(?<!\\) (?: # if group 2 was start, escaped parenthesis is end (?(2)\\\)| # if group 3 was start, escaped bracket is end (?(3)\\\]| # else group 4 was start, match end equation \\end\{equation\} ) )))

Comment: else

Non-Capturing Group(?: # greedily and recursively match everything in between # groups 2, 3 and 4 support recursion (.*(?R)?.*)(?<!\\) (?: # if group 2 was start, escaped parenthesis is end (?(2)\\\)| # if group 3 was start, escaped bracket is end (?(3)\\\]| # else group 4 was start, match end equation \\end\{equation\} ) )))

Comment: greedily and recursively match everything in between

Comment: groups 2, 3 and 4 support recursion

Group 6(.*(?R)?.*)

.*any character (except for line terminators), repeated any number of times

(?R)?optionally recurses into the entire pattern

.*any character (except for line terminators), repeated any number of times

Negative Lookbehind(?<!\\)

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

Non-Capturing Group(?: # if group 2 was start, escaped parenthesis is end (?(2)\\\)| # if group 3 was start, escaped bracket is end (?(3)\\\]| # else group 4 was start, match end equation \\end\{equation\} ) ))

Comment: if group 2 was start, escaped parenthesis is end

Condition(?(2)\\\)| # if group 3 was start, escaped bracket is end (?(3)\\\]| # else group 4 was start, match end equation \\end\{equation\} ) )

Uses the first branch if group 2 matched

If the condition is true, match this branch:\\\)

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

\)the literal ) (41₁₀ / 51₈ / 29₁₆)

Otherwise, match this branch: # if group 3 was start, escaped bracket is end (?(3)\\\]| # else group 4 was start, match end equation \\end\{equation\} )

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

25 tokens

Regular Expression

(?<!\\)    # negative look-behind to make sure start is not escaped 
(?:        # start non-capture group for all possible match starts
  # group 1, match dollar signs only 
  # single or double dollar sign enforced by look-arounds
  ((?<!\$)\${1,2}(?!\$))|
  # group 2, match escaped parenthesis
  (\\\()|
  # group 3, match escaped bracket
  (\\\[)|                 
  # group 4, match begin equation
  (\\begin\{equation\})
)
# if group 1 was start
(?(1)
  # non greedy match everything in between
  # group 1 matches do not support recursion
  (.*?)(?<!\\)
  # match ending double or single dollar signs
  (?<!\$)\1(?!\$)|  
# else
(?:
  # greedily and recursively match everything in between
  # groups 2, 3 and 4 support recursion
  (.*(?R)?.*)(?<!\\)
  (?:
    # if group 2 was start, escaped parenthesis is end
    (?(2)\\\)|  
    # if group 3 was start, escaped bracket is end
    (?(3)\\\]|     
    # else group 4 was start, match end equation
    \\end\{equation\}
  )
))))

New

NOTE: For test purposes each test has been contained to one line, please enable the s flag for multi-line matches.

$ match $ don't match nested $ match $

$$ no match$
$no match$$
\\$no match\\$
$no match\\$
\\$no match\\$

$$ match $$ don't match nested $$ match $$

$$$ no match $$
$$ no match $$$
\\$$ no match$$
$$ no match\\$$
\\$$ no match\\$$

\( match \)
\( 1 \(  nested match  \) 3 \)

\\( no match \\)
\( no match \\\\)
\\\\( no match \\\\)

\[ match \]
\[ 1 \[ nested match \] 3 \]

\\\\[ no match \\]
\\[ no match \\\\]
\\\\[ no match \\\\]

\begin{equation} match \end{equation}
\begin{equation} 1 \begin{equation} nested match \end{equation} \end{equation}

\\\\begin{equation} no match \\end{equation}
\\begin{equation} no match \\\\end{equation}
\\\\begin{equation} no match \\end{equation}

Extraction

NOTE: For test purposes each test has been contained to one line, please enable the s flag for multi-line matches.

$ match $ don't match nested $ match $

$$ no match$
$no match$$
\\$no match\\$
$no match\\$
\\$no match\\$

$$ match $$ don't match nested $$ match $$

$$$ no match $$
$$ no match $$$
\\$$ no match$$
$$ no match\\$$
\\$$ no match\\$$

\( match \)
\( 1 \(  nested match  \) 3 \)

\\( no match \\)
\( no match \\\\)
\\\\( no match \\\\)

\[ match \]
\[ 1 \[ nested match \] 3 \]

\\\\[ no match \\]
\\[ no match \\\\]
\\\\[ no match \\\\]

\begin{equation} match \end{equation}
\begin{equation} 1 \begin{equation} nested match \end{equation} \end{equation}

\\\\begin{equation} no match \\end{equation}
\\begin{equation} no match \\\\end{equation}
\\\\begin{equation} no match \\end{equation}