C strtok() Function with NULL Argument: Tokenizing String Parts

The first argument of `strtok` is the string to be tokenized, and the second argument is a string containing all the delimiters. In this code, the first call to `strtok` tokenizes the string `data` using space as the delimiter. The second call to `strtok` continues tokenizing the remaining part of the string, but instead of providing the original string `data` again, `NULL` is passed as the first argument. Passing `NULL` as the first argument tells `strtok` to continue tokenizing the same string that was tokenized in the previous call. It allows the function to continue where it left off and tokenize the remaining part of the string.