src/tty.c

   1 /* tty -- print the path of the terminal connected to standard input
   2    Copyright (C) 90, 91, 92, 93, 94, 1995 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 2, or (at your option)
   7    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, write to the Free Software
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 /* Displays "not a tty" if stdin is not a terminal.
  19    Displays nothing if -s option is given.
  20    Exit status 0 if stdin is a tty, 1 if not, 2 if usage error,
  21    3 if write error.
  22
  23    Written by David MacKenzie <djm@gnu.ai.mit.edu>.  */
  24
  25 #include <config.h>
  26 #include <stdio.h>
  27 #include <getopt.h>
  28 #include <sys/types.h>
  29
  30 #include "system.h"
  31 #include "version.h"
  32 #include "error.h"
  33
  34 static void usage ();
  35
  36 /* The name under which this program was run. */
  37 char *program_name;
  38
  39 /* If nonzero, return an exit status but produce no output. */
  40 static int silent;
  41
  42 /* If non-zero, display usage information and exit.  */
  43 static int show_help;
  44
  45 /* If non-zero, print the version on standard output and exit.  */
  46 static int show_version;
  47
  48 static struct option const longopts[] =
  49 {
  50   {"help", no_argument, &show_help, 1},
  51   {"silent", no_argument, NULL, 's'},
  52   {"quiet", no_argument, NULL, 's'},
  53   {"version", no_argument, &show_version, 1},
  54   {NULL, 0, NULL, 0}
  55 };
  56
  57 void
  58 main (argc, argv)
  59      int argc;
  60      char **argv;
  61 {
  62   char *tty;
  63   int optc;
  64
  65   program_name = argv[0];
  66   silent = 0;
  67
  68   while ((optc = getopt_long (argc, argv, "s", longopts, (int *) 0)) != EOF)
  69     {
  70       switch (optc)
  71         {
  72         case 0:
  73           break;
  74
  75         case 's':
  76           silent = 1;
  77           break;
  78
  79         default:
  80           usage (2);
  81         }
  82     }
  83
  84   if (show_version)
  85     {
  86       printf ("tty - %s\n", version_string);
  87       exit (0);
  88     }
  89
  90   if (show_help)
  91     usage (0);
  92
  93   if (optind != argc)
  94     usage (2);
  95
  96   tty = ttyname (0);
  97   if (!silent)
  98     {
  99       if (tty)
 100         puts (tty);
 101       else
 102         puts ("not a tty");
 103
 104       if (ferror (stdout) || fclose (stdout) == EOF)
 105         error (3, errno, "standard output");
 106     }
 107
 108   exit (isatty (0) ? 0 : 1);
 109 }
 110
 111 static void
 112 usage (status)
 113      int status;
 114 {
 115   if (status != 0)
 116     fprintf (stderr, "Try `%s --help' for more information.\n",
 117              program_name);
 118   else
 119     {
 120       printf ("Usage: %s [OPTION]...\n", program_name);
 121       printf ("\
 122 Print the file name of the terminal connected to standard input.\n\
 123 \n\
 124   -s, --silent, --quiet   print nothing, only return an exit status\n\
 125       --help              display this help and exit\n\
 126       --version           output version information and exit\n\
 127 ");
 128     }
 129   exit (status);
 130 }