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/* vi: set sw=4 ts=4: */
/*
* mesg implementation for busybox
*
* Copyright (c) 2002 Manuel Novoa III <mjn3@codepoet.org>
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config MESG
//config: bool "mesg (1.4 kb)"
//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_NOFORK(mesg, mesg, BB_DIR_USR_BIN, BB_SUID_DROP, mesg))
//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"
#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)
#endif
int mesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mesg_main(int argc UNUSED_PARAM, char **argv)
{
struct stat sb;
mode_t m;
char c = 0;
argv++;
if (argv[0]
&& (argv[1] || ((c = argv[0][0]) != 'y' && c != 'n'))
) {
bb_show_usage();
}
/* We are a NOFORK applet.
* (Not that it's very useful, but code is trivially NOFORK-safe).
* Play nice. Do not leak anything.
*/
if (!isatty(STDIN_FILENO))
bb_simple_error_msg_and_die("not a tty");
xfstat(STDIN_FILENO, &sb, "stdin");
if (c == 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 (fchmod(STDIN_FILENO, m) != 0)
bb_perror_nomsg_and_die();
return EXIT_SUCCESS;
}
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