The [optional other stuff] was meant to say that you may have other options you want to pass to gcc - e.g. "-O3" to give you the highest level of optimization, or "-ansi" to ensure that your code is ANSI-C - there are literally hundreds of different options that gcc can be given. A text-file is not one of those. The information that your code needs to open "myfile.txt" is already in the source code.
It also says:
10-2.c:10: warning: empty body in an if-statement
What do you think that means?