main (argc, argv)
        int argc;
        char *argv[];
{
        extern char *optarg;
        extern int  optind;
        int         sopt = 0, jopt = 0, error = 0, c;
        long        length = 0;

        while ( ( c = getopt(argc, argv, "sjl:") ) != EOF )
                switch (c) {
                        case 's':
                                sopt = 1;
                                break;
                        case 'j':
                                jopt = 1;
                                break;
                        case 'l':
                                length = atol (optarg);
                                printf ("length are %d\n", length);

                                if ( length <= 0 ) {
                                        printf ("bad length\n");
                                        error = 1;
                                }
                                break;
                        case '?':
                                error = 1;
                                break;
                        default:
                                printf ("bug\n");
                                exit (1);
                }

        if (error) {
                printf ("Usage: my programme [-s] [-j] [-i len] [file...]\n");
                exit (2);
        }
}