hello.c

#include <stdio.h>

void main(int argc, char* argv[]) {
	if (argc < 2)
		printf("Hello world!\n");
	else if (argc == 2)
		printf("Hello %s!\n", argv[1]);
	else {
		printf("Hello ");
		printf(argv[1]);
		for (int i=2; i < argc; i++)
			printf(", %s", argv[i]);
		printf("!\n");
	}
}