enforce zero options

[Jan Stary]

Some programs in bin/ and usr.bin/ use the following idiom
to make sure that there are no options present:
 
        while ((ch = getopt(argc, argv, "")) != -1)
                switch (ch) {
                case '?':
                default:
                        usage();
                        /* NOTREACHED */
                }

        if (argc != optind) {
                usage();
                /* NOTREACHED */
        }
 
Why is this better then simply checking that (argc == 1)?

Below is a diff to logname as an example.
(Remove the pointless locale while there.)

        Jan


Index: logname.c
===================================================================
RCS file: /cvs/src/usr.bin/logname/logname.c,v
retrieving revision 1.9
diff -u -p -r1.9 logname.c
--- logname.c   9 Oct 2015 01:37:08 -0000       1.9
+++ logname.c   12 Oct 2016 08:38:49 -0000
@@ -32,7 +32,6 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <locale.h>
 #include <unistd.h>
 #include <err.h>
 
@@ -44,23 +43,11 @@ main(int argc, char *argv[])
        int ch;
        char *p;
 
-       setlocale(LC_ALL, "");
-
        if (pledge("stdio", NULL) == -1)
                err(1, "pledge");
 
-       while ((ch = getopt(argc, argv, "")) != -1)
-               switch (ch) {
-               case '?':
-               default:
-                       usage();
-                       /* NOTREACHED */
-               }
-
-       if (argc != optind) {
+       if (argc != 1)
                usage();
-               /* NOTREACHED */
-       }
 
        if ((p = getlogin()) == NULL)
                err(1, NULL);