regex match after word

Question

I would like to know how to capture text only if the beginning of a line matching a certain string... but i dont want to capture the begining string...

for example if i have the text:

BEGIN_TAG: Text To Capture

WRONG_TAG: Text Not to Capture

i want to capture:

Text To Capture

From the line that begin with BEGIN_TAG: not the line that begin with WRONG_TAG:

I know the how to select the line that begin with the desired text: ^BEGIN_TAG:\W?(.*)

but this selects the text "BEGIN_TAG:"... i dont want this only want the text after "BEGIN_TAG"

I am using PCRE regex

Answer 1

Instead of a positive lookbehind that does not allow unknown width patterns, you may use a match reset operator \K:

^BEGIN_TAG:\W?\K.*

See the regex demo

Details:

• ^ - in Sublime, start of a line
• BEGIN_TAG: - a string of literal chars
• \W? - 1 or 0 non-word chars
• \K - the match reset operator that discards all text matched so far
• .* - any 0+ chars other than linebreak characters (the rest of the line) that are the only chars that will be kept in the matched text.

Answer 2

You can use lookbehind. Then, the text in the lookbehind group isn't part of the whole match. You can see it as an anchor like \b, ^, etc.

You then get:

(?<=^BEGIN_TAG:\W)(\w.*)$

Explained:

(?<=             # Positive lookbehind group
    ^            # Start of line / string
    BEGIN_TAG:   # Literal
    \W           # A non-word character ([^a-zA-Z_])
)
(                # First and only matching group (probably not needed)
    \w           # A word character ([a-zA-Z_])
    .*           # Any character, any number of times
)
$                # End of line / string