7.8. Command Line Arguments

Gamma provides a mechanism for accessing command line arguments. The symbol argv contains a list of the parsed command line arguments. Thus, if you have an application named my_app which takes two arguments arg1 and arg2, then the executable invoked with:

    		my_app arg1 arg2
    		

will receive the following argv:

    		(my_app arg1 arg2)
    		

Like any list, the length of argv is simply length (argv); The command line arguments can be accessed like any list, using any of the following sample approaches:

      	  
    for ( i=0; i < length(argv); i++)
    {
        arg = car (nth_cdr (argv, i));
        ... process arg ...
    }
    	  

or similarly, but more efficient:

    while (length (argv) > 0)
    {
        arg = car (argv);
        ... process arg ...
        argv = cdr (argv);
    }
    	  

which can also be expressed, still more efficiently, and without modifying the original argv, with:

    for (i=argv; i; i = cdr(i))
    {
        arg = car (i);
        ... process arg ...
    }