How to split strings and use them as commands in C++?

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C++

I have defined some functions in a class that changes or print or read information from a linked list : add_book(int booknum) / print_book and so on ..
the user writes a command like :add 123
I want my program to split the string into :string"add" and int"123" and run the add_book(int booknum)(i.e: use "add" as a keyword to run the function add_book)

What I have tried:

at first I thought we can use argc,argv to solve the problem but argv is always considered as a string (char)