src/tty.c

   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 "error.h"
  31 #include "quote.h"
  32
  33 /* Exit statuses.  */
  34 enum
  35   {
  36     TTY_STDIN_NOTTY = 1,
  37     TTY_FAILURE = 2,
  38     TTY_WRITE_ERROR = 3
  39   };
  40
  41 /* The official name of this program (e.g., no 'g' prefix).  */
  42 #define PROGRAM_NAME "tty"
  43
  44 #define AUTHORS proper_name ("David MacKenzie")
  45
  46 /* If true, return an exit status but produce no output. */
  47 static bool silent;
  48
  49 static struct option const longopts[] =
  50 {
  51   {"silent", no_argument, NULL, 's'},
  52   {"quiet", no_argument, NULL, 's'},
  53   {GETOPT_HELP_OPTION_DECL},
  54   {GETOPT_VERSION_OPTION_DECL},
  55   {NULL, 0, NULL, 0}
  56 };
  57
  58 void
  59 usage (int status)
  60 {
  61   if (status != EXIT_SUCCESS)
  62     emit_try_help ();
  63   else
  64     {
  65       printf (_("Usage: %s [OPTION]...\n"), program_name);
  66       fputs (_("\
  67 Print the file name of the terminal connected to standard input.\n\
  68 \n\
  69   -s, --silent, --quiet   print nothing, only return an exit status\n\
  70 "), stdout);
  71       fputs (HELP_OPTION_DESCRIPTION, stdout);
  72       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  73       emit_ancillary_info (PROGRAM_NAME);
  74     }
  75   exit (status);
  76 }
  77
  78 int
  79 main (int argc, char **argv)
  80 {
  81   int optc;
  82
  83   initialize_main (&argc, &argv);
  84   set_program_name (argv[0]);
  85   setlocale (LC_ALL, "");
  86   bindtextdomain (PACKAGE, LOCALEDIR);
  87   textdomain (PACKAGE);
  88
  89   initialize_exit_failure (TTY_WRITE_ERROR);
  90   atexit (close_stdout);
  91
  92   silent = false;
  93
  94   while ((optc = getopt_long (argc, argv, "s", longopts, NULL)) != -1)
  95     {
  96       switch (optc)
  97         {
  98         case 's':
  99           silent = true;
 100           break;
 101
 102         case_GETOPT_HELP_CHAR;
 103
 104         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 105
 106         default:
 107           usage (TTY_FAILURE);
 108         }
 109     }
 110
 111   if (optind < argc)
 112     {
 113       error (0, 0, _("extra operand %s"), quote (argv[optind]));
 114       usage (TTY_FAILURE);
 115     }
 116
 117   errno = ENOENT;
 118
 119   if (silent)
 120     return isatty (STDIN_FILENO) ? EXIT_SUCCESS : TTY_STDIN_NOTTY;
 121
 122   int status = EXIT_SUCCESS;
 123   char const *tty = ttyname (STDIN_FILENO);
 124
 125   if (! tty)
 126     {
 127       tty = _("not a tty");
 128       status = TTY_STDIN_NOTTY;
 129     }
 130
 131   puts (tty);
 132   return status;
 133 }