How to capture everything until another capture group - regex

Question

I have the following template :
1251 Left Random Text I want to fill
It can go through multiple lines
As you can see
9841 Right Again we see a lot of random text with 3115 numbers
And this also goes
To multiple lines
0121 Right
5151 Right This one is just one line
I was wrong
9731 Left This one is just a line
5123 NA Instruction 5151 was wrong
4113 Right Instr 9841 was correct
We checked
I want to have 3 groups:
1251
Left
Random Text I want to fill
It can go through multiple lines
As you can see
I'm using
(\d+)\s(\w+)\s(.*)
but it stops at the current line only (so I get only Random Text I want to fill in group 3, although I want including As you can see)
If I'm using Single line flag I get only 1 match for each group, group 3 almost being all
Here is live : https://regex101.com/r/W3x0mH/4

Answer 1

You could use a repeating group matching all the lines while asserting that the next line does not start wit 1+ digits followed by Left or Right:
(\d+)\s(\w+)\s(.*(?:\r?\n(?!\d).*)*)
Explanation
(\d+)\s(\w+)\s Match the first 2 groups
(Third capturing group
.* Match 0+ times any char except a newline
(?: Non capturing group
\r?\n(?!\d).* Match newline, assert what is on the right is not a digit
)* Close non capturing group and repeat 0+ times
) Close capturing group
Regex demo

Answer 2

You may use this regex with a lookahead:
^(\d+)\s(\w+)\s(.*?)(?=\n\d|\z)
with DOTALL and MULTILINE modifiers.
Updated Regex Demo
RegEx Details:
^: Line start
(\d+): Match and capture 1+ digits in group #1
\s: match a whitespace
(\w+): Match and capture 1+ word characters in group #2
\s: match a whitespace
(.*?): Match 0 or more of any character (non-greedy) provided next lookahead assertion is satiSfied
(?=\n\d|\z): Lookahead assertion to assert that we have a newline followed by a digit or there is end of input
Faster Regex:
If you are using this regex on a long string then you should also keep overall performance in mind as a regex with DOTALL modifier will tend to get slow on a large size text. For that I suggest using this regex that doesn't need DOTALL modifier:
^(\d+)\s(\w+)\s(.*(?:\n.*)*?)(?=\n\d|\z)
RegEx Demo 2
On regex101 demo this regex takes just 181 steps as compared to first one that takes 1300 steps.

Answer 3

For the third group, repeat any character while using negative lookahead for ^\d, which would indicate the start of a new match:
(\d+)\s(\w+)\s((?:(?!^\d)[\s\S])*)
https://regex101.com/r/W3x0mH/5

Answer 4

You may try with this regex:
^(\d+)\s+(\w+)\s+(.*?)(?=^\d|\z)
^(\d+)\s+ , ^\d+ Line begins with numbers followed by one or more whitespace character \s+
(\w+)\s+ where \w+ one or more characters (left,right,na or something else) followed by one or more whitespace \w+
(.*?) matches everything until it finds a line beginning with number or \z end of string.
I think it fits your requirement....
Regex101