Add whoami(1)

including manpage and other stuff. This program is a no-brainer.
This was inspired by an initial commit by e@bestmx.net. Thanks!

whoami.c

@@ -0,0 +1,37 @@
+/* See LICENSE file for copyright and license details. */
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <pwd.h>
+
+#include "util.h"
+
+static void
+usage (void)
+{
+	eprintf("usage: %s\n", argv0);
+}
+
+int
+main (int argc, char *argv[])
+{
+	uid_t uid;
+	struct passwd *pw;
+
+	argv0 = argv[0], argc--, argv++;
+
+	if (argc)
+		usage();
+
+	uid = geteuid();
+	errno = 0;
+	if (!(pw = getpwuid(uid))) {
+		if (errno)
+			eprintf("getpwuid %d:", uid);
+		else
+			eprintf("getpwuid %d: no such user\n", uid);
+	}
+	puts(pw->pw_name);
+
+	return fshut(stdout, "<stdout>");
+}