expr(1): Add support for -- as required by POSIX

Reported-By: vstemen on #dragonflybsd

diff --git a/bin/expr/expr.y b/bin/expr/expr.y
index 0bcd6e0..4807d9d 100644 (file)
--- a/bin/expr/expr.y
+++ b/bin/expr/expr.y
@@ -244,12 +244,25 @@ is_zero_or_null(struct val *vp)
        /* NOTREACHED */
 }
 
+static void
+usage(void)
+{
+        fprintf(stderr,
+                "usage: expr expression\n");
+        exit(EXIT_FAILURE);
+}
+
 int
-main (int argc __unused, char **argv)
+main (int argc, char **argv)
 {
        setlocale (LC_ALL, "");
 
-       av = argv + 1;
+       if (argc > 1 && strcmp(argv[1], "--"))
+               av = argv + 1;
+       else if (argc > 2)
+               av = argv + 2;
+       else
+               usage();
 
        yyparse ();