manual/examples/termios.c

   1 /* Noncanonical Mode Example
   2    Copyright (C) 1991-2023 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License
   6    as published by the Free Software Foundation; either version 2
   7    of the License, or (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
  18 #include <unistd.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <termios.h>
  22
  23 /* Use this variable to remember original terminal attributes. */
  24
  25 struct termios saved_attributes;
  26
  27 void
  28 reset_input_mode (void)
  29 {
  30   tcsetattr (STDIN_FILENO, TCSANOW, &saved_attributes);
  31 }
  32
  33 void
  34 set_input_mode (void)
  35 {
  36   struct termios tattr;
  37
  38   /* Make sure stdin is a terminal. */
  39   if (!isatty (STDIN_FILENO))
  40     {
  41       fprintf (stderr, "Not a terminal.\n");
  42       exit (EXIT_FAILURE);
  43     }
  44
  45   /* Save the terminal attributes so we can restore them later. */
  46   tcgetattr (STDIN_FILENO, &saved_attributes);
  47   atexit (reset_input_mode);
  48
  49 /*@group*/
  50   /* Set the funny terminal modes. */
  51   tcgetattr (STDIN_FILENO, &tattr);
  52   tattr.c_lflag &= ~(ICANON|ECHO); /* Clear ICANON and ECHO.  */
  53   tattr.c_cc[VMIN] = 1;
  54   tattr.c_cc[VTIME] = 0;
  55   tcsetattr (STDIN_FILENO, TCSAFLUSH, &tattr);
  56 }
  57 /*@end group*/
  58
  59 int
  60 main (void)
  61 {
  62   char c;
  63
  64   set_input_mode ();
  65
  66   while (1)
  67     {
  68       read (STDIN_FILENO, &c, 1);
  69       if (c == '\004')          /* @kbd{C-d} */
  70         break;
  71       else
  72         write (STDOUT_FILENO, &c, 1);
  73     }
  74
  75   return EXIT_SUCCESS;
  76 }