Using the string
A B x C x D - E x F
I am trying to capture the groups A B C and D but not E or F.
My understanding of regex is that I want everything before \sx\s up to the \s-\s,
so I would start with .*(?=\sx\s),
which I want to happen as many times until I reach the \s-\s.
My result is (.*(?=\sx\s))*.*(?=\s-\s) which returns A B x C x D.
I think this may have to do with the way lookaheads work but I am lost on what to change.
Using a positive lookahead (?=\s-\s), the pattern must be present in the data.
If you want to match AB, C and D and also want to match those values if this part - E x F is not present, you could make use of a quantifier in a negative lookbehind:
(?<!\s-\s.*)[A-Z](?:\s[A-Z])*
Explanation
(?<!\s-\s.*) Negative lookbehind, assert what is on the left is not \s-\s[A-Z] Match a char A-Z(?: Non capture group
\s[A-Z] Math whitespace char followed by A-Z)* Close group and repeat 0+ times