More specifically for the file method, take a look at:
file_find and
file_str_read

Through only the basic string functions in Gamestudio, assuming your set format for the parameter, you can iterate through each character in the string and place the non-whitespaces into an array of integers.

Otherwise, there are many C/C++ threads online related to basic string manipulation. In your case, you can search for something like "string to array of ints" in C.