regex101: PCRE (Legacy) Match Workspace

1st Alternative(?xs) outer-start(?:(?!inner-start).)*?outer-end

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

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

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

outer-startthe literal text outer-start (case sensitive)

Non-Capturing Group(?:(?!inner-start).)*?

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

Negative Lookahead(?!inner-start)

inner-startthe literal text inner-start (case sensitive)

.any character

outer-endthe literal text outer-end (case sensitive)

2nd Alternative outer-start(?:(?!outer-end).)*?inner-end(?:(?!outer-end).)*?s\.*?outer-end

outer-startthe literal text outer-start (case sensitive)

Non-Capturing Group(?:(?!outer-end).)*?

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

Negative Lookahead(?!outer-end)

outer-endthe literal text outer-end (case sensitive)

.any character

inner-endthe literal text inner-end (case sensitive)

Non-Capturing Group(?:(?!outer-end).)*?

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

Negative Lookahead(?!outer-end)

outer-endthe literal text outer-end (case sensitive)

.any character

sthe literal s (115₁₀ / 163₈ / 73₁₆) (case sensitive)

\.*?the literal . (46₁₀ / 56₈ / 2E₁₆) , repeated any number of times

outer-endthe literal text outer-end (case sensitive)

3rd Alternative inner-start\s*(text-that-i-want)\s*inner-end

inner-startthe literal text inner-start (case sensitive)

\s*any whitespace character, repeated any number of times

Group 1(text-that-i-want)

text-that-i-wantthe literal text text-that-i-want (case sensitive)

\s*any whitespace character, repeated any number of times

inner-endthe literal text inner-end (case sensitive)

Global pattern flags

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

Search reference

Regular Expression

(?xs)
outer-start(?:(?!inner-start).)*?outer-end|
outer-start(?:(?!outer-end).)*?inner-end(?:(?!outer-end).)*?s\.*?outer-end|
inner-start\s*(text-that-i-want)\s*inner-end

New

outer-start some unwanted text inner-start text-that-i-want inner-end some more  text outer-end
outer-start some  text inner-start text-that-i-want inner-end some more unwanted text outer-end
outer-start some  text inner-start text-that-i-want inner-end some more  text outer-end
outer-start some  text inner-start text-that-i-want inner-end some more unwanted text outer-end

Regular Expressions 101

Regular Expression

Extraction