regex101: PCRE (Legacy) Match Workspace

(?xsm)applies the following effective flags to the remainder of the pattern: xsm

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

s modifier: single line. Allows a dot to match line terminators

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

Comment: free-spacing mode, DOTALL, multi-line

Positive Lookahead(?=.*?blue)

.*?any character, repeated any number of times

bluethe literal text blue (case sensitive)

Comment: if blue isn't there, fail without delay

Comment: ########## LINE SKIPPER / COUNTER ############

Non-Capturing Group(?: # start non-capture group # the aim is to skip lines that don't contain blue # and capture a corresponding digit sequence (?: # skip one line that doesn't contain blue ^ # beginning of line (?:(?!blue)[^\r\n])* # zero or more chars # that do not start blue (?:\r?\n) # newline chars ) # With each line skipped, let Group 1 capture # an ever-increasing portion of the string of numbers (?= # lookahead [^~]+ # skip all chars that are not tildes ( # start Group 1 (?(1)\1) # if Group 1 is set, match Group 1 # (?>\1?) # alternate phrasing for the above ~\d+ # match a tilde and digits ) # end Group 1 ) # end lookahead )*+

*+repeats the group contents below any number of times:

Comment: start non-capture group

Comment: the aim is to skip lines that don't contain blue

Comment: and capture a corresponding digit sequence

Non-Capturing Group(?: # skip one line that doesn't contain blue ^ # beginning of line (?:(?!blue)[^\r\n])* # zero or more chars # that do not start blue (?:\r?\n) # newline chars )

Comment: skip one line that doesn't contain blue

^start of line

Comment: beginning of line

Non-Capturing Group(?:(?!blue)[^\r\n])*

*repeats the group contents below any number of times:

Negative Lookahead(?!blue)

bluethe literal text blue (case sensitive)

Negated Character Class[^\r\n]

\ra carriage return (ASCII 13)

\na line-feed (newline) character (ASCII 10)

Comment: zero or more chars

Comment: that do not start blue

Non-Capturing Group(?:\r?\n)

\r?optionally matches a carriage return (ASCII 13)

\na line-feed (newline) character (ASCII 10)

Comment: newline chars

Comment: With each line skipped, let Group 1 capture

Comment: an ever-increasing portion of the string of numbers

Positive Lookahead(?= # lookahead [^~]+ # skip all chars that are not tildes ( # start Group 1 (?(1)\1) # if Group 1 is set, match Group 1 # (?>\1?) # alternate phrasing for the above ~\d+ # match a tilde and digits ) # end Group 1 )

Comment: lookahead

Negated Character Class[^~]+

+matches at least one character outside the set below:

~the literal ~ (126₁₀ / 176₈ / 7E₁₆)

Comment: skip all chars that are not tildes

Group 1( # start Group 1 (?(1)\1) # if Group 1 is set, match Group 1 # (?>\1?) # alternate phrasing for the above ~\d+ # match a tilde and digits )

Comment: start Group 1

Condition(?(1)\1)

Uses the first branch if group 1 matched

If the condition is true, match this branch:\1

\1the text saved by group 1

Comment: if Group 1 is set, match Group 1

Comment: (?>\1?) # alternate phrasing for the above

~the literal text ~

\d+a digit, repeated at least once

Comment: match a tilde and digits

Comment: end Group 1

Comment: end lookahead

Comment: end counter-line-skipper: zero or more times

Comment: the possessive + forbids backtracking

.*?any character, repeated any number of times

Comment: lazily match any chars up to...

blue the literal text blue (case sensitive)

Comment: match blue

Negated Character Class[^~]+

+matches at least one character outside the set below:

~the literal ~ (126₁₀ / 176₈ / 7E₁₆)

Comment: match any non-tilde chars

Condition(?(1)\1)

Uses the first branch if group 1 matched

If the condition is true, match this branch:\1

\1the text saved by group 1

Comment: if Group 1 has been set, match it

Comment: \1? # alternate phrasing for the above

~ the literal text ~

Comment: match a tilde

\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match

Comment: drop what we matched so far

\d+a digit, repeated at least once

Comment: match digits. This is the match!

25 tokens

Regular Expression

(?xsm)             # free-spacing mode, DOTALL, multi-line
(?=.*?blue)        # if blue isn't there, fail without delay

########### LINE SKIPPER / COUNTER ############
(?:               # start non-capture group
                  # the aim is to skip lines that don't contain blue
                  # and capture a corresponding digit sequence
   (?:               # skip one line that doesn't contain blue
      ^              # beginning of line
      (?:(?!blue)[^\r\n])*  # zero or more chars
                            # that do not start blue
      (?:\r?\n)      # newline chars
    )   
# With each line skipped, let Group 1 capture
# an ever-increasing portion of the string of numbers
   (?=             # lookahead
      [^~]+           # skip all chars that are not tildes
      (               # start Group 1
        (?(1)\1)      # if Group 1 is set, match Group 1
        # (?>\1?)     # alternate phrasing for the above
        ~\d+          # match a tilde and  digits
      )               # end Group 1
   )               # end lookahead
)*+               # end counter-line-skipper: zero or more times
                  # the possessive + forbids backtracking


.*?               # lazily match any chars up to...
blue              # match blue
[^~]+             # match any non-tilde chars
(?(1)\1)          # if Group 1 has been set, match it
# \1?             # alternate phrasing for the above
~                 # match a tilde
\K                # drop what we matched so far
\d+               # match digits. This is the match!

Unit Tests

There are no unit tests, click to add some.