Question

I am looking for a very simple explanation/tutorial on what flags are. I understand that flags work indicate a command what to do. For example:

rm -Rf test

I know that the rm command will remove the test folder and that the -Rf flags will force the command to erase not just the folder but the files in it.

But, where are the flags read/compiled??? What handles the flags? Can I, for example, write my own C/C++ program and designate different flags so that the program does different things? I hope I am asking the right questions. If not, please let me know.

Answer 1

This simple program should demonstrate the arguments passed to the program (including the program name itself.)

Parsing, interpreting and using those arguments is up to the programmer (you), although there are libraries available to help:

int main(int argc, char* argv[])
{
    int i;
    for(i=0; i<argc; ++i)
    {   printf("Argument %d : %s\n", i, argv[i]);
    }
    return 0;
}

---

If you compile this program into a.out, and run it as:

prompt$>  ./a.out ParamOne ParamTwo -rf x.c

You should see output:

Argument 0 : a.out
Argument 1 : ParamOne
Argument 2 : ParamTwo
Argument 3 : -rf
Argument 4 : x.c