How can I use regex to validate an inputed string similarly to this outlined structure?

Question

The structure I want the regex to validate in looks similar to this:

keyword input(param_input,param_input2)

The "keyword" section needs to be built into the regex so it's not considered an input.

The input, param_input and param_input2 can be letters(including caps), numbers and _, but none of these inputs can be entirely numbers.

What would be the best approach for writing a regex string to validate a string?

Attempt:

function+\s+[a-zA-Z0-9]+((?!.*[,]{2})(?!.*[,0-9]{2})(?!^$,{1})[a-zA-Z0-9,]*)

A warning: while a regex for simple comma-separated tokens is easy and can work well, things get much more complicated if you also want to allow strings that include a comma, like in `keyword myinput(myparam1, "string1,string2")`. In that case, a regex is not the ideal solution. — cornuz, Sep 07 '21 at 16:10
@hiteshbedre function+\s+[a-zA-Z0-9]+$(?!.*[,]{2})(?!.*[,0-9]{2})(?!^$,{1})[a-zA-Z0-9,]*$ — Programing, Sep 07 '21 at 20:10
Assuming you're matching code, most languages don't allow identifiers to start with a digit, so the terms would be either all digits `\d+` or `(?=\D)\w+` — Bohemian, Sep 08 '21 at 05:22

Niel Godfrey Pablo Ponciano · Accepted Answer · 2021-09-08T05:03:08.683

You can use negative lookahead assertions to make sure that the characters you are capturing isn't purely digits. Try this:

^[\w]+ (?!\d+\()([\w]+)\((?:(?!\d+[,\)])(\w+)),(?:(?!\d+[,\)])(\w+))\)$

Demo here.

keyword input(param_input,param_input2)  -> Will match
keyword 12345(param_input,param_input2)
keyword in123(abc123_DEF4,a1_b2_C3_d45)  -> Will match
keyword input(12345678901,param_input2)
keyword input(param_input,123456789012)
keyword input(12345678901,123456789012)
keyword XYZ98(aaaa1111BB2,CCCCCCC33333)  -> Will match
keyword XYZ98(aaaa1111BB2,CCCCCCC33333,DD44)

Where:

^[\w]+ - Match the initial string e.g. keyword
(?!\d+\()([\w]+)\( - Using a negative lookahead assertion, match the next part until ( only if it isn't purely digits e.g. input( but not 12345(
(?:(?!\d+[,\)])(\w+)), - Again using a negative lookahead assertion, match the next part until , only if it isn't purely digits e.g. param_input, but not 12345678901,
(?:(?!\d+[,\)])(\w+))\)$ - Again using a negative lookahead assertion, match the next part until the ending ) only if it isn't purely digits e.g. param_input2) but not 123456789012))

This is fixed to 2x input parameters e.g. (param_input,param_input2). Note that if you wish to accept variable amount of input parameters e.g. (param1,param2,param3,...,paramN), you can't easily do it with regex groups as explained in this answer from another thread.

What you can do instead is manually define this (?:(?!\d+[,\)])(\w+)), for every additional parameter.

References:

https://www.ocpsoft.org/tutorials/regular-expressions/and-in-regex/

How can I use regex to validate an inputed string similarly to this outlined structure?

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