src/tty.c

   1 /* tty -- print the name of the terminal connected to standard input
   2    Copyright (C) 1990-2024 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 }