uniq: Lobotomize for POSIX-subset compatibility

POSIX uniq(1) is required to write to its second argument,
if one is given.
The multiple-input feature I accidentally added might be useful,
but users and scripts who rely on it would be put at risk for data loss
if they ever run into a POSIX uniq(1).

TODO

@@ -54,8 +54,6 @@ tr string1 [string2]
 
 unexpand [-a] [-t N] [file...]
 
-uniq [-diuc] [input [output]]
-
 unlink file
 
 who 

uniq.c

@@ -41,12 +41,13 @@ main(int argc, char *argv[])
 
 	if(optind == argc)
 		uniq(stdin, "<stdin>");
-	else for(; optind < argc; optind++) {
+	else if(optind == argc - 1) {
 		if(!(fp = fopen(argv[optind], "r")))
 			eprintf("fopen %s:", argv[optind]);
 		uniq(fp, argv[optind]);
 		fclose(fp);
-	}
+	} else
+		enprintf(2, "too many arguments\n");
 	uniq_finish();
 
 	return EXIT_SUCCESS;