do not fail build if MAXSYMLINKS isn't defined

[oweals/busybox.git] / init / mesg.c

diff --git a/init/mesg.c b/init/mesg.c
index cfb517f60a4d43aebfa8ff9fdd02a7b93b52ece0..45c13b8e030e5fa3fe6446830ad6262b17fe8ac3 100644 (file)
--- a/init/mesg.c
+++ b/init/mesg.c
@@ -4,43 +4,73 @@
  *
  * Copyright (c) 2002 Manuel Novoa III  <mjn3@codepoet.org>
  *
- * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
 
+//config:config MESG
+//config:      bool "mesg"
+//config:      default y
+//config:      help
+//config:        Mesg controls access to your terminal by others. It is typically
+//config:        used to allow or disallow other users to write to your terminal
+//config:
+//config:config FEATURE_MESG_ENABLE_ONLY_GROUP
+//config:      bool "Enable writing to tty only by group, not by everybody"
+//config:      default y
+//config:      depends on MESG
+//config:      help
+//config:        Usually, ttys are owned by group "tty", and "write" tool is
+//config:        setgid to this group. This way, "mesg y" only needs to enable
+//config:        "write by owning group" bit in tty mode.
+//config:
+//config:        If you set this option to N, "mesg y" will enable writing
+//config:        by anybody at all. This is not recommended.
+
+//applet:IF_MESG(APPLET(mesg, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_MESG) += mesg.o
+
+//usage:#define mesg_trivial_usage
+//usage:       "[y|n]"
+//usage:#define mesg_full_usage "\n\n"
+//usage:       "Control write access to your terminal\n"
+//usage:       "       y       Allow write access to your terminal\n"
+//usage:       "       n       Disallow write access to your terminal"
+
 #include "libbb.h"
 
-#ifdef USE_TTY_GROUP
-#define S_IWGRP_OR_S_IWOTH     S_IWGRP
+#if ENABLE_FEATURE_MESG_ENABLE_ONLY_GROUP
+#define S_IWGRP_OR_S_IWOTH  S_IWGRP
 #else
-#define S_IWGRP_OR_S_IWOTH     (S_IWGRP | S_IWOTH)
+#define S_IWGRP_OR_S_IWOTH  (S_IWGRP | S_IWOTH)
 #endif
 
 int mesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int mesg_main(int argc, char **argv)
+int mesg_main(int argc UNUSED_PARAM, char **argv)
 {
        struct stat sb;
-       const char *tty;
+       mode_t m;
        char c = 0;
 
-       if (--argc == 0
-        || (argc == 1 && ((c = **++argv) == 'y' || c == 'n'))
+       argv++;
+
+       if (argv[0]
+        && (argv[1] || ((c = argv[0][0]) != 'y' && c != 'n'))
        ) {
-               tty = ttyname(STDERR_FILENO);
-               if (tty == NULL) {
-                       tty = "ttyname";
-               } else if (stat(tty, &sb) == 0) {
-                       mode_t m;
-                       if (argc == 0) {
-                               puts((sb.st_mode & (S_IWGRP|S_IWOTH)) ? "is y" : "is n");
-                               return EXIT_SUCCESS;
-                       }
-                       m = (c == 'y') ? sb.st_mode | S_IWGRP_OR_S_IWOTH
-                                      : sb.st_mode & ~(S_IWGRP|S_IWOTH);
-                       if (chmod(tty, m) == 0) {
-                               return EXIT_SUCCESS;
-                       }
-               }
-               bb_simple_perror_msg_and_die(tty);
+               bb_show_usage();
+       }
+
+       if (!isatty(STDIN_FILENO))
+               bb_error_msg_and_die("not a tty");
+
+       xfstat(STDIN_FILENO, &sb, "stderr");
+       if (c == 0) {
+               puts((sb.st_mode & (S_IWGRP|S_IWOTH)) ? "is y" : "is n");
+               return EXIT_SUCCESS;
        }
-       bb_show_usage();
+       m = (c == 'y') ? sb.st_mode | S_IWGRP_OR_S_IWOTH
+                      : sb.st_mode & ~(S_IWGRP|S_IWOTH);
+       if (fchmod(STDIN_FILENO, m) != 0)
+               bb_perror_nomsg_and_die();
+       return EXIT_SUCCESS;
 }