正则表达式与NOT选项匹配C＃

Question

I have the following text input-

Host             Expiration  Features            
**172.17.64.120    never**       CPSM-C-BASE CPSB-NPM CPSB-EPM CPSB-LOGS CPSB-MNTR CPSB-MPTL CPSB-UDIR CPSB-PRVS CPSB-GBLP CK-77B458DF8D52
**172.17.64.120    never**       CPSM-C-U CPSB-NPM CPSB-EPM CPSB-LOGS CPSB-MNTR CPSB-MPTL CPSB-UDIR CPSB-PRVS CPSB-GBLP CK-FF18475CE402
**10.10.5.17       10May2018**   CPSM-C-U CPSB-NPM CPSB-EPM CPSB-LOGS CPSB-MNTR 

(some other text..)

LICENSE **10.10.5.17 10May2018** 
LICENSE **172.17.64.120 never** 
LICENSE **172.17.64.120 never** 

I want to get all the 3 licenses without duplication - The following regex pattern - \\d+\\.\\d+\\.\\d+\\.\\d+\\s*(\\d{1,2}[a-zA-Z]{3}\\d{4} |never) matches these results:

172.17.64.120    never
172.17.64.120    never
10.10.5.17       10May2018
10.10.5.17 10May2018
172.17.64.120 never
172.17.64.120 never

The issue is, that I want to get the results without duplications. Is there anyway to insert additional not option to the regex that will not match the last 3 result (those who start with LICENSE+spaces)

10.10.5.17 10May2018
172.17.64.120 never
172.17.64.120 never

Thanks :)

Answer 1

If i understand what you are saying... If your regex is working, then don't complicated it, just use a Distinct on the results

List<string> results = <put your matches in here>;

results = results.Distinct();

Enumerable.Distinct Method (IEnumerable)

Returns distinct elements from a sequence by using the default equality comparer to compare values.

Answer 2

You may prepend your pattern with a word boundary and a negative lookbehind that will fail the matches after LICENSE + one or more whitespaces:

\b(?<!\bLICENSE\s+)(\d{1,3}(?:\.\d{1,3}){3})\s*(\d{1,2}[a-zA-Z]{3}\d{4}|never)\b

See the regex demo .

Details

• \\b - a word boundary
• (?<!\\bLICENSE\\s+) - immediately to the left of the current location, there can't be LICENSE followed with 1+ whitespace chars
• (\\d{1,3}(?:\\.\\d{1,3}){3}) - Group 1: one, two or three digits, and then 3 occurrences of a dot followed with 1 to 3 digits
• \\s* - 0+ whitespaces
• (\\d{1,2}[a-zA-Z]{3}\\d{4}|never) - 1 or 2 digits, 3 ASCII letters and 4 digits, or a whole word never
• \\b - word boundary.