dmesg(8): fail if given positional arguments

[Scott Cheloha]

dmesg(8) doesn't use any positional arguments.  It's a usage error if
any are present.

ok?

Index: dmesg.c
===================================================================
RCS file: /cvs/src/sbin/dmesg/dmesg.c,v
retrieving revision 1.31
diff -u -p -r1.31 dmesg.c
--- dmesg.c     24 Dec 2019 13:20:44 -0000      1.31
+++ dmesg.c     2 Aug 2022 16:48:13 -0000
@@ -89,6 +89,9 @@ main(int argc, char *argv[])
        argc -= optind;
        argv += optind;
 
+       if (argc != 0)
+               usage();
+
        if (memf == NULL && nlistf == NULL) {
                int mib[2], msgbufsize;
                size_t len;