regular expression to find a pattern of string but not following another pattern of string

[peter tong]

Example, I have a string
openshift.cluster_id:20bd0f2c-0d96-4c9a-b730-b4db9de53ce4

I want to use regular expression to find another string start with "openshift.cluster_id:" but not follow the pattern "20bd0f2c-0d96-4c9a-b730-b4db9de53ce4", how to do this?

[Stephan van Hulst]

Do you have an example of a string that you want to match, and an example of a string that should not match?

[peter tong]

peter tong wrote:Example, I have a string
openshift.cluster_id:20bd0f2c-0d96-4c9a-b730-b4db9de53ce4

I want to use regular expression to find another string start with "openshift.cluster_id:" but not follow the pattern "20bd0f2c-0d96-4c9a-b730-b4db9de53ce4", how to do this?

I found this regular expression, using Negative lookahead, fulfill my criteria:

openshift.cluster_id:(?!20bd0f2c-0d96-4c9a-b730-b4db9de53ce4)

openshift.cluster_id:20bd0f2c-0d96-4c9a-b730-b4db9de53ce4 not find any match
openshift.cluster_id:02bd0f2c-0d96-4c9a-b730-b4db9de53ce4 find a match
openshift.cluster_id:120bd0f2c-0d96-4c9a-b730-b4db9de53ce4 find a match

Another similar example
find a string match "abc", but then not follow "def"
use regex:

abc(?!def)

abcdef => not find any match
abcedf => find a match
abcfde => find a match
abcdefa => not find any match
abcadef => find a match

Detail can be seen in this link
https://www.regular-expressions.info/lookaround.html
about negative lookahead

[fred rosenberger]

Does it have to be a single regular expression?

If possible, I'd do it in two passes...one pass to find strings with "openshift.cluster_id:", and then another that of those, filters out the ones you don't want.

I HATE complicated regular expression.  They are tricky to write correctly, hard to test, and next to impossible to remember what you were doing when you come back to them six months later (or next week, in my case).  Two simple regex's are much easier to follow than one complicated one.

[Paul Clapham]

In fact, does it even need to be a regular expression? It looks to me like you just want

if (s.startsWith("blabla") && ! s.endsWith("yaddayadda"))

since you already used regex to find "blabla" and "yaddayadda".

[Mike Simmons]

Unless you're searching within a much larger area, like a file, and the "openshift.cluster_id:" occurrs multiple times, and you're looking for the ones that aren't followed by the specific cluster id 20bd0f2c-0d96-4c9a-b730-b4db9de53ce4.  The openshift.cluster_id: isn't necessarily at the beginning, and the value isn't necessarily at the end.

Negative lookahead is exactly the tool for this problem, I think.  The regex syntax isn't very complicated at all.  Unfortunately, the cluster id looks like a unsightly mess.  But that doesn't make it a complicated regex.

Unfortunately, we should note that "openshift.cluster_id:" does contain one special character: '.'  For that, the regex should actually replace "." with "\."  And if this is being done within a Java program, you need to escape again, so that each "." is replaced with "\\\.".  Annoying.

Peter, glad you found the answer!