#include <stdio.h>
#include <stdlib.h>

static void hello(char *name)
{
	if (name != NULL)
		printf("Hello, %s!\n", name);
}

int main(int argc, char **argv)
{
	int i;

	if (argc == 1)
		hello(getenv("USER"));

	for (i = 1; i < argc; i++)
		hello(argv[i]);

	exit(EXIT_SUCCESS);
}