I'm trying to build my own console and I'm using the below statement to get RAW access so I can implement some advanced features such as implementing the auto suggest feature that's implemented in a BASH shell by pressing the TAB key.
system("/bin/stty raw")
When using this, the enter key (and others) doesn't behave normally and when I press enter, it displays ^M and doesn't go to the next line.
How do I set the RAW console to go to the next line when it receives ^M
Also can I set the Shell to NOT display the keys pressed so I can send the char back to the console with putchar() (so ^M doesn't display when pressed).
Thanks
How do I set the RAW console to go to the next line when it receives ^M
You write an appropriate control code to the console when you read an ^M. The whole point of raw mode is that the console does not do things like recognize line ends, backspaces, etc., etc., because you want to handle them yourself. Once you do that, you need to handle all those things.
can I set the Shell to NOT display the keys pressed
Sure. Turn off echo. With the stty command, you would use stty raw -echo but if you're doing this from a C program, you'd be much better off using the terminal API. See man tcsetattr
Related
I'm writing a C program that requires to hide the characters a user types from the screen during the program execution. For example, when running the following loop
while (1)
{
//do some work
}
the console displays the blinking cursor (that's good). BUT, when the user types keys on the keyboard, these keys are being echoed out to the console. To visualize it better:
Step 1: Starting the program
root#debian:/home/root# ./program
_
Step 2: User types some characters (even though he shouldn't)
root#debian:/home/root# ./program
AdajfsaSJ_
The characters get echoed on the console. How can I stop this? I know it's theoretically possible, but I can't find out how to implement it.
If you need a better example for what I want to achieve, use the screen command on an empty serial port. screen /dev/tty30 for example. This empties the console and runs the program, HOWEVER, the user is not able to enter any characters (there's a blinking white cursor block and no keyboard characters are being echoed to the console). That's what I need.
Any insight would help, thanks!
Use termios() to turn off the ECHO flag of the terminal.
To turn off the text cursor, use the termcap library to control the cursor visibility.
I am using the following code to read and output each keystroke without having to press enter each time.
system("\bin\stty raw");
Right after I finish reading, the program does another system call to reset the terminal behaviour.
system("\bin\stty cooked");
The thing is, the last line is not resetting the terminal behavior as it should. Everything gets messed up once this program terminates. It continues to read input and does not do anything once an enter or CTRL C or anything else is pressed.
How can I reset the terminal behavior to the one it initially was please?
Use popen() and pclose() to run "/bin/stty -g". Read the output from stty -g] and save it for later.
When you want to reset the terminal, use "/bin/stty the-string-from-stty-g".
The mechanics are fiddly but doable.
The whole point of the -g option to stty is to give a string that can be passed back to stty to reinstate the current settings. You can then run your stty raw, ensuring that you reset the terminal before you exit using the string from stty -g.
Note, too, that stty sane does a good job of resetting aberrant terminals to a known state. You may need to run: Control-Jstty saneControl-J at the terminal command line to make it work.
You can also do it without running external programs. You'll need to look at tcgetattr() and
tcsetattr() and related functions. Again, you read the current settings (tcgetattr() et al), change a copy of them and set those as the new values, and ensure that you reset the original settings on exit (maybe with atexit()?).
i am writing a terminal chat and would like to reprint the content the user has typed in, if a new message from another user has arrived asynchronously.
if a new message arrives i print "\x1B[2K" to stdout (ANSI ESCAPE CODE for erasing the current line) to clear the current line, then i print "\r" to move the cursor to the leftmost position, then i print the received message with a newline
now i would like to reprint the characters the user has typed - i found out that there is a special character VREPRINT (http://www.gnu.org/software/libc/manual/html_node/Editing-Characters.html) that can be used and if a hit CTRL-R it actually works... but if print the character to stdout using the character placed in c_cc[VREPRINT] of a struct termios, it does not work - is it even possible to do it that way?
I do not want to use any other libraries like readline or ncurses, since this would be plain overkill... i just would like to make my solution work using ICANON terminal mode if possible
Thanks in advance!
While it is possible to write to the same tty device that you are reading from, this doesn't mean that the characters that appear will be processed as input characters.
You can test this yourself, using two separate shell sessions (using screen, tmux, or, if you are on MacOSX, iTERM.app sessions).
in Session 1, get the current tty name:
tty
Let's assume the tty name of Session 1 is /dev/ttys000.
Then enter the following, without a return or newline -- just leave it pending:
echo abc def-
In Session 2 (using the tty name from Session 1), enter the following command:
echo foo >/dev/ttys000
The string foo should appear on the pending line in Session 1, like this:
echo abc def-foo
Now, go back to Session 1, and hit an "enter" (or return), causing the input buffer to be completed and sent to the shell, which will parse the first word as the echo command, with the subsequent arguments as text to be printed.
You should see the string "abc def-" echoed -- but not the foo.
This test makes it clear that the string foo was never placed into the input buffer, even though it was sent to the same tty being used for input (and output).
You can try to see if special control characters are recognized and processed; but they won't be. These characters are only being output to the terminal, but not processed.
In order for the special characters to be processed, they have to be received via the socket connected to the input device.
To accomplish what you are trying to do, you'll have to go non-canonical (stty -icanon) and process every character in your code, in order to collect the pending input and also be able to produce asynchronous output.
Alternatively, using nurses is not hard at all, and if you are writing a terminal-based chat program, I would suggest creating at least two panels: a "chat" panel for all output, and an "input" panel for user input. This allows output from other users, as well as the completed commands from the "input" panel, to be received and written to the "chat" panel asynchronously without disturbing the current command in progress by the user in the "input" panel.
I have this program in C that reads the input like this:
cod1 = getch ();
if (kbhit())
cod2 = getch ();
I can read every Ctrl+Char possible sequences, except for Ctrl+C, that closes the program - that is OK, and Ctrl+S, that simple is not catch. But I wanted to make Ctrl+S to be the save function in my program; how could I do that? Furthermore, is it possible to read Alt+Char characters? Because it reads it as a regular character, e.g., Alt+A is read with the same codes as A.
Your problem is that input probably gets eaten by terminal emulator.
For example Alt+<Whatever> is often reserved for menu shortcuts (e.g. Alt+F opens File menu). Matching characters are often hilighted once you hold Alt (F get's underscored in File).
Ctrl+S is reserved for Stops all output on screen (XOFF) (again your terminal emulator does that).
As for using Alt+<...> as shortcuts in your command line application. As far as I'm concerned holding Alt doesn't affect character received, it just sets flags which are hard to access in console. Even in GUI application (in Windows) it's quite tricky and you have to use function like GetAsyncState() to check whether alt was pressed.
All,
I have a little utility written in C that requires the user to press a key to make a menu selection. The code is predictably simple:
system("stty raw");
save_ID = getchar();
system("stty cooked");
It grabs the keystroke and doesn't need to wait for ENTER. It works fine from the command line, however, when I try to bind the command to a hotkey in Gnome/metacity, it waits for the keystroke alright, but the keystroke seems to be processed not as as input to the command, but as if it were a separate command. Eg. if my keystroke is "1" and I'm in a terminal I see:
"zsh: command not found: 1"
I've tried it without the "system" lines, but nothing changed. Is there perhaps some special version of "getchar" that works with the GUI? Incidentally, a non-interactive version of the program works fine when bound to a hotkey, so the program is basically functional, it just can't be used interactively.
Thanks
I believe GTK may interest you, although I've never personally used it.
http://www.gtk.org/
.
You should also be able to run gnome-terminal. Using /opt/appFoo/appFoo as the command to run your app normally, you would run
gnome-terminal -e "/opt/appFoo/appFoo" &