1  /* tty -- print the name of the terminal connected to standard input
       2     Copyright (C) 1990-2023 Free Software Foundation, Inc.
       3  
       4     This program is free software: you can redistribute it and/or modify
       5     it under the terms of the GNU General Public License as published by
       6     the Free Software Foundation, either version 3 of the License, or
       7     (at your option) any later version.
       8  
       9     This program is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12     GNU General Public License for more details.
      13  
      14     You should have received a copy of the GNU General Public License
      15     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      16  
      17  /* Displays "not a tty" if stdin is not a terminal.
      18     Displays nothing if -s option is given.
      19     Exit status 0 if stdin is a tty, 1 if not a tty, 2 if usage error,
      20     3 if write error.
      21  
      22     Written by David MacKenzie <djm@gnu.ai.mit.edu>.  */
      23  
      24  #include <config.h>
      25  #include <stdio.h>
      26  #include <getopt.h>
      27  #include <sys/types.h>
      28  
      29  #include "system.h"
      30  #include "quote.h"
      31  
      32  /* Exit statuses.  */
      33  enum
      34    {
      35      TTY_STDIN_NOTTY = 1,
      36      TTY_FAILURE = 2,
      37      TTY_WRITE_ERROR = 3
      38    };
      39  
      40  /* The official name of this program (e.g., no 'g' prefix).  */
      41  #define PROGRAM_NAME "tty"
      42  
      43  #define AUTHORS proper_name ("David MacKenzie")
      44  
      45  /* If true, return an exit status but produce no output. */
      46  static bool silent;
      47  
      48  static struct option const longopts[] =
      49  {
      50    {"silent", no_argument, nullptr, 's'},
      51    {"quiet", no_argument, nullptr, 's'},
      52    {GETOPT_HELP_OPTION_DECL},
      53    {GETOPT_VERSION_OPTION_DECL},
      54    {nullptr, 0, nullptr, 0}
      55  };
      56  
      57  void
      58  usage (int status)
      59  {
      60    if (status != EXIT_SUCCESS)
      61      emit_try_help ();
      62    else
      63      {
      64        printf (_("Usage: %s [OPTION]...\n"), program_name);
      65        fputs (_("\
      66  Print the file name of the terminal connected to standard input.\n\
      67  \n\
      68    -s, --silent, --quiet   print nothing, only return an exit status\n\
      69  "), stdout);
      70        fputs (HELP_OPTION_DESCRIPTION, stdout);
      71        fputs (VERSION_OPTION_DESCRIPTION, stdout);
      72        emit_ancillary_info (PROGRAM_NAME);
      73      }
      74    exit (status);
      75  }
      76  
      77  int
      78  main (int argc, char **argv)
      79  {
      80    int optc;
      81  
      82    initialize_main (&argc, &argv);
      83    set_program_name (argv[0]);
      84    setlocale (LC_ALL, "");
      85    bindtextdomain (PACKAGE, LOCALEDIR);
      86    textdomain (PACKAGE);
      87  
      88    initialize_exit_failure (TTY_WRITE_ERROR);
      89    atexit (close_stdout);
      90  
      91    silent = false;
      92  
      93    while ((optc = getopt_long (argc, argv, "s", longopts, nullptr)) != -1)
      94      {
      95        switch (optc)
      96          {
      97          case 's':
      98            silent = true;
      99            break;
     100  
     101          case_GETOPT_HELP_CHAR;
     102  
     103          case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
     104  
     105          default:
     106            usage (TTY_FAILURE);
     107          }
     108      }
     109  
     110    if (optind < argc)
     111      {
     112        error (0, 0, _("extra operand %s"), quote (argv[optind]));
     113        usage (TTY_FAILURE);
     114      }
     115  
     116    errno = ENOENT;
     117  
     118    if (silent)
     119      return isatty (STDIN_FILENO) ? EXIT_SUCCESS : TTY_STDIN_NOTTY;
     120  
     121    int status = EXIT_SUCCESS;
     122    char const *tty = ttyname (STDIN_FILENO);
     123  
     124    if (! tty)
     125      {
     126        tty = _("not a tty");
     127        status = TTY_STDIN_NOTTY;
     128      }
     129  
     130    puts (tty);
     131    return status;
     132  }