# include <stdio.h>
char * getenv();

main(argc, argv)
int argc;
char **argv;
{
    char * val;
    if (argc  != 3) {
        fprintf(stderr, "Usage: %s option←name default\n", argv[0]);
        exit(1);
    }
    val = getenv(argv[1]);
    printf(" -%s %s ", argv[1], (val? val : argv[2]));
}