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| |
| <h3 class="section">17.7 Noncanonical Mode Example</h3> |
| |
| <p>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. |
| |
| <pre class="smallexample"> #include <unistd.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <termios.h> |
| |
| /* <span class="roman">Use this variable to remember original terminal attributes.</span> */ |
| |
| 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; |
| |
| /* <span class="roman">Make sure stdin is a terminal.</span> */ |
| if (!isatty (STDIN_FILENO)) |
| { |
| fprintf (stderr, "Not a terminal.\n"); |
| exit (EXIT_FAILURE); |
| } |
| |
| /* <span class="roman">Save the terminal attributes so we can restore them later.</span> */ |
| tcgetattr (STDIN_FILENO, &saved_attributes); |
| atexit (reset_input_mode); |
| |
| /* <span class="roman">Set the funny terminal modes.</span> */ |
| tcgetattr (STDIN_FILENO, &tattr); |
| tattr.c_lflag &= ~(ICANON|ECHO); /* <span class="roman">Clear ICANON and ECHO.</span> */ |
| 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') /* <kbd>C-d</kbd> */ |
| break; |
| else |
| putchar (c); |
| } |
| |
| return EXIT_SUCCESS; |
| } |
| </pre> |
| <p>This program is careful to restore the original terminal modes before |
| exiting or terminating with a signal. It uses the <code>atexit</code> |
| function (see <a href="Cleanups-on-Exit.html#Cleanups-on-Exit">Cleanups on Exit</a>) to make sure this is done |
| by <code>exit</code>. |
| |
| <p>The shell is supposed to take care of resetting the terminal modes when |
| a process is stopped or continued; see <a href="Job-Control.html#Job-Control">Job Control</a>. 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. |
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