I want to match a section of a string that contains certain characters repeated, along with certain other characters only given a certain criteria. For instance matching characters a-z contained in angle brackets and numbers only if the number is preceeded by a plus.
Matching <abcde> to abcde.
<abcde1> should not match anything.
Matching <abcde+1> to abcde+1
Matching <abcde+1asd+2+3+4as> to abcde+1asd+2+3+4as
<abcde+> should not match anything.
The regex I've tried is <([a-z]|(\+(?=[0-9])|[0-9](?<=[\+])))*>.
You can use
(?<=<)(?:[a-zA-Z]+(?:\+\d+)*)+[a-zA-Z]*(?=>)
<((?:[a-zA-Z]+(?:\+\d+)*)+[a-zA-Z]*)>
See the regex demo. Details:
(?<=<) - a positive lookbehind that requires a < char immediately on the left(?:[a-zA-Z]+(?:\+\d+)*)+ - one or more occurrences of
[a-zA-Z]+ - one or more letters(?:\+\d+)* - zero or more sequences of + and one or more digits[a-zA-Z]* - one or more ASCII letters(?=>) - a positive lookahead that requires a > char immediately on the right.