ubbctl/ubbctl.c (main): add command line processing and usage display

ubbctl/ubbctl.c

@@ -12,7 +12,9 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <stdio.h>
+#include <unistd.h>
 
 #include <ubb/ubb.h>
 
@@ -44,14 +46,36 @@ static void show_pins(void)
 			printf("%d", !!(PDDAT & p->mask));
 		else
 			putchar(PDPULL & p->mask ? 'Z' : 'R');
-
 	}
 	printf("\n");
 }
 
 
+static void usage(const char *name)
+{
+        fprintf(stderr,
+"usage: %s\n"
+    , name);
+	exit(1);
+}
+
 int main(int argc, char **argv)
 {
+	int c;
+
+	while ((c = getopt(argc, argv, "")) != EOF)
+		switch (c) {
+		default:
+			usage(*argv);
+		}
+
+	switch (argc-optind) {
+	case 0:
+		break;
+	default:
+		usage(*argv);
+	}
+
 	ubb_open(UBB_ALL);
 	show_pins();
 	return 0;