You can use different methods to specify main to receive arguments from the
command line the following program shows three methods followed by some code:

#include 
int main(int argc,int argv[]) {
int main(int argc,char **argv) {
int main(int argc, char *argv[]) {
	if(argc > 1)
		system(argv[1]);
	else
		printf("No argument\n");
	return 0;
}

This program (minus two of the int main() calls) uses one argument from the
command line and calls that argument as a system call. This example is from
a setuid root program which a user can gain root access.

Other methods:

main(argc, argv)
	int argc;
	char **argv;
	char *argv[];
{
	code...
}