GNU Info

(libc.info)Noncanon Example

---

Next: Pseudo-Terminals Prev: Line Control Up: Low-Level Terminal Interface

---

Enter node , (file) or (file)node

Noncanonical Mode Example
=========================

   Here is an example program that shows how you can set up a terminal
device to read single characters in noncanonical input mode, without
echo.

     #include <unistd.h>
     #include <stdio.h>
     #include <stdlib.h>
     #include <termios.h>
     
     /* Use this variable to remember original terminal attributes. */
     
     struct termios saved_attributes;
     
     void
     reset_input_mode (void)
     {
       tcsetattr (STDIN_FILENO, TCSANOW, &saved_attributes);
     }
     
     void
     set_input_mode (void)
     {
       struct termios tattr;
       char *name;
     
       /* Make sure stdin is a terminal. */
       if (!isatty (STDIN_FILENO))
         {
           fprintf (stderr, "Not a terminal.\n");
           exit (EXIT_FAILURE);
         }
     
       /* Save the terminal attributes so we can restore them later. */
       tcgetattr (STDIN_FILENO, &saved_attributes);
       atexit (reset_input_mode);
     
       /* Set the funny terminal modes. */
       tcgetattr (STDIN_FILENO, &tattr);
       tattr.c_lflag &= ~(ICANON|ECHO); /* Clear ICANON and ECHO. */
       tattr.c_cc[VMIN] = 1;
       tattr.c_cc[VTIME] = 0;
       tcsetattr (STDIN_FILENO, TCSAFLUSH, &tattr);
     }
     
     int
     main (void)
     {
       char c;
     
       set_input_mode ();
     
       while (1)
         {
           read (STDIN_FILENO, &c, 1);
           if (c == '\004')          /* `C-d' */
             break;
           else
             putchar (c);
         }
     
       return EXIT_SUCCESS;
     }

   This program is careful to restore the original terminal modes before
exiting or terminating with a signal.  It uses the `atexit' function
(Note: Cleanups on Exit) to make sure this is done by `exit'.

   The shell is supposed to take care of resetting the terminal modes
when a process is stopped or continued; see Note: Job Control.  But
some existing shells do not actually do this, so you may wish to
establish handlers for job control signals that reset terminal modes.
The above example does so.