add dirname

dirname.c

@@ -0,0 +1,18 @@
+/* See LICENSE file for copyright and license details. */
+#include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "util.h"
+
+int
+main(int argc, char *argv[])
+{
+	if(getopt(argc, argv, "") != -1)
+		exit(EXIT_FAILURE);
+	if(optind != argc-1)
+		eprintf("usage: %s string\n", argv[0]);
+
+	puts(dirname(argv[optind]));
+	return EXIT_SUCCESS;
+}