coreutils/tty.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * tty implementation for busybox
   4  *
   5  * Copyright (C) 2003  Manuel Novoa III  <mjn3@codepoet.org>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9
  10 /* BB_AUDIT SUSv4 compliant */
  11 /* http://www.opengroup.org/onlinepubs/9699919799/utilities/tty.html */
  12
  13 //usage:#define tty_trivial_usage
  14 //usage:       ""
  15 //usage:#define tty_full_usage "\n\n"
  16 //usage:       "Print file name of stdin's terminal"
  17 //usage:        IF_INCLUDE_SUSv2( "\n"
  18 //usage:     "\n        -s      Print nothing, only return exit status"
  19 //usage:        )
  20 //usage:
  21 //usage:#define tty_example_usage
  22 //usage:       "$ tty\n"
  23 //usage:       "/dev/tty2\n"
  24
  25 #include "libbb.h"
  26
  27 int tty_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  28 int tty_main(int argc UNUSED_PARAM, char **argv)
  29 {
  30         const char *s;
  31         IF_INCLUDE_SUSv2(int silent;)  /* Note: No longer relevant in SUSv3. */
  32         int retval;
  33
  34         xfunc_error_retval = 2;  /* SUSv3 requires > 1 for error. */
  35
  36         IF_INCLUDE_SUSv2(silent = getopt32(argv, "s");)
  37         IF_INCLUDE_SUSv2(argv += optind;)
  38         IF_NOT_INCLUDE_SUSv2(argv += 1;)
  39
  40         /* gnu tty outputs a warning that it is ignoring all args. */
  41         bb_warn_ignoring_args(argv[0]);
  42
  43         retval = EXIT_SUCCESS;
  44
  45         s = xmalloc_ttyname(STDIN_FILENO);
  46         if (s == NULL) {
  47         /* According to SUSv3, ttyname can fail with EBADF or ENOTTY.
  48          * We know the file descriptor is good, so failure means not a tty. */
  49                 s = "not a tty";
  50                 retval = EXIT_FAILURE;
  51         }
  52         IF_INCLUDE_SUSv2(if (!silent) puts(s);)
  53         IF_NOT_INCLUDE_SUSv2(puts(s);)
  54
  55         fflush_stdout_and_exit(retval);
  56 }