Show usage and exit non-zero for unsupported option in tred

Towards https://gitlab.com/graphviz/graphviz/-/issues/1843.

diff --git a/cmd/tools/tred.c b/cmd/tools/tred.c
index a96053735a3569d3c9ff783b21055fd0083a3ac3..386b1f23d4aafd24d4c38f125e7aa80eb25f96ec 100644 (file)
--- a/cmd/tools/tred.c
+++ b/cmd/tools/tred.c
@@ -259,9 +259,11 @@ static void init(int argc, char *argv[])
        case '?':
            if (optopt == '?')
                usage(0);
-           else
-               fprintf(stderr, "%s: option -%c unrecognized - ignored\n",
+           else {
+               fprintf(stderr, "%s: option -%c unrecognized\n",
                        CmdName, optopt);
+               usage(1);
+           }
            break;
        }
     }