Text macros - replace them with function result

I need to introduce some text macros, for example:

"Some text here, some text here #from_file[a.txt,2,N] and here and here"

The #from_file[a.txt,2,N] macro should get 2 random lines from a.txt and join them with new line character another #from_file[a.txt,5,S] - tak开发者_JS百科e 5 random lines and join with space

I of course need some another macros: #random[0-9] - random number, #random[A-B,5] - random string with 5 characters

Macros can be in another format etc: {from_file:a.txt,2,N}

My first idea was to use regular expressions - but maybe exist another solution for my problem?

It sounds like you want to create some sort of "general purpose" text-macro system, and while I'm sure this can be done with regexps, what you want basically boil down to what you want to be capable of, and how extensive & flexible it needs to be.

You basically need to define your grammar and constraints. Can the file-name contain the macro-block terminator-character '}' ? If so, does it need to be escaped? Should escaping be supported? Are spaces within a macro-block allowed?

Basically find out how you want things to work, preferably as constrained as possible, as this means you can implement a simpler solution, and there might not be any need for a full blown parser and similar ilk.

Maybe a regex-based solution will be sufficient (although most certainly not very good). But before you can tell that, you need to spec better ;)