characters between two delimiters

Question

Trying to put a regex expression together that returns the string between _ and _$ (where $ is the end of the string).

input:

abc_def_ghi_

desired regex outcoume:

def_ghi

I've tried quite a few combinations such as thsi.

((([^_]*){1})[^_]*)_$

any help appreciated.

Note: the regex above returns abc_def, and not the desired def_ghi.

score 4 · Accepted Answer · answered Jun 21 '12 at 06:27

4

So it's everything between the first _ and the final _ (both excluding)?

Then try

(?<=_).*(?=_$)

(hoping you're not using JavaScript)

Explanation:

(?<=_)  # Assert that the previous character is a _
.*      # Match any number of characters...
(?=_$)  # ... until right before the final, string-ending _

answered Jun 21 '12 at 06:27

Tim Pietzcker

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for me this returns { "abc_, "_" }. – sgtz Jun 21 '12 at 06:43
1

@sgtz: You need to use the `Regex.Match()` method, not `Regex.Split()`. – Tim Pietzcker Jun 21 '12 at 06:44

score 1 · Answer 2 · answered Jun 21 '12 at 06:28

You could try to use the greedyness of operators to your advantage:

^.*?_(.*)_$

matches everything from the start (non-greedy), up to an underscore, and from this underscore on to the end of the string, where it expects and underscore, then the end of the string, and captures it in the first match.

^    Beginning of string
.*?  Any number of characters, at least 0
_    Anchor-tag, literal underscore
(.*) Any number of characters, greedy
_    Anchor-tag, literal underscore
$    End of string

I'm not sure why you are using .split(). Using a regular match with the mentioned RegEx should return one captured group, the one you were looking for. — 0xCAFEBABE, Jun 21 '12 at 08:18

score 0 · Answer 3 · edited Aug 17 '16 at 09:24

I was searching for this within a larger log entry:

"threat_name":"PUP.Optional.Wajam"

The format enclosed the field name in double quotes then a colon then the value in double quotes.

Here's what I ended up with to avoid punctuation breaking the regex..

threat_name["][:]["](?P<signature>.*?)["]

(from regex101.com)

threat_name matches the characters threat_name literally (case sensitive)
["] match a single character present in the list below
" a single character in the list " literally (case sensitive)
[:] match a single character present in the list below
: the literal character :
["] match a single character present in the list below
" a single character in the list " literally (case sensitive)
(?P<signature>.*?) Named capturing group signature
.*? matches any character (except newline)
Quantifier: *? Between zero and unlimited times, as few times as possible, expanding as needed [lazy]
["] match a single character present in the list below
" a single character in the list " literally (case sensitive)

characters between two delimiters

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