simple input output question

Yes, you need to tokenize.

For a do-it-yourself approach:

Tokenize into character/digit strings (identifiers or literal constants) and punctuation (separators, operators). Discard white spaces, including comments. Do not forget operators that occur as pairs like ++, >= ...

Try and find the declarations. For this, you will need to split the whole file into statements (token sequences terminated by a colon ; ) and function definitions (token sequences terminated by a block {...}). Make sure to match the braces in pairs to obtain full blocks. You can ignore the block content.

Now among the remaining definitions, you should find those having a pair of parenthesis (). These are the function declarations (unless they appear at the right of an equal sign, meaning that they are initializer calls).

Parsing the complete function signature (attributes, return type, argument types and argument names) shouldn't be such a big deal, checking for , separators. Always make sure to match internal quotes, brackets, parenthesis or angle bracket in pairs.