How to use regex to split by last occurrence of underscore

May 5, 2022

I want to split lines by last occurrence of underscore like this :

Input :

MANY_TIME_T1=PANORAMA17
MANY_TIME_T2=OK STATUS
MANY_TIME_T1=PANORAMA18
MANY_TIME_T2=OK STATUS
COMMENT=OK
LAST<LIGNE1

Output :

Match 1 : MANY_TIME_T1=PANORAMA17
Group 1 : MANY_TIME
Group 2 : T1
Group 3 : =
Group 4 : PANORAMA17

Match 2 : MANY_TIME_T2=OK STATUS
Group 1 : MANY_TIME
Group 2 : T2
Group 3 : =
Group 4 : OK STATUS

Match 3 : MANY_TIME_T1=PANORAMA18
Group 1 : MANY_TIME
Group 2 : T1
Group 3 : =
Group 4 : PANORAMA18

Match 4 : MANY_TIME_T2=OK STATUS
Group 1 : MANY_TIME
Group 2 : T2
Group 3 : =
Group 4 : OK STATUS

Match 5 : COMMENT=OK
Group 1 : COMMENT
Group 3 : =
Group 4 : OK

Match 6 : LAST<LIGNE1
Group 1 : LAST
Group 3 : <
Group 4 : LIGNE1

I try this regex ^\s*([^_<>=]+)(_\w+)?([<>=%])(.*)$ to split by underscore but it can’t split by last occurence like as above.

Demo

>Solution :

You can use

^\s*(\w+?)(?:_([^\W_]+))?([<>=%])(.*)

See the regex demo.

Details:

^ – start of string
\s* – zero or more whitespaces
(\w+?) – Group 1: one or more word chars, as few as possible
(?:_([^\W_]+))? – an optional occurrence of _ and the one or more word chars except underscore captured into Group 2
([<>=%]) – Group 3: one of the specified chars
(.*) – Group 4: the rest of the line.