Keyboard input emulation...

[emiliouy]

Hi guys,

I’m on Debian 5.0.7 and I want to write a simple C/C++ console application that emulates keyboard keystrokes, without using graphical mode (unable to use XLib stuff: XSendEvent, etc, etc).

The solutions I’ve found on the web involve an X-Server behind, so I need a more basic, low-level way to do that I think, any ideas?

PD: to understand the big picture I found this: http://www.subspacefield.org/~travis/keyboard/index.html, but it wasn’t enough :(

Thanks in advance,
e-milio.

[barriehie]

Like a socket type thing???

[emiliouy]

Why did you have modified this?

"barriehie (2) ... Jan 7, 2011 at 7:59pm
Have to be a bit more specific about 'emulate'. :) If you write chars to /dev/tty it will 'emulate' characters coming from the keyboard but if you call interrupt 16 with the appropriate registers loaded it will actually put a keystroke in the keyboard buffer."

After some extra Google, I’ve found: http://expect-lite.sourceforge.net/expect-lite_simple.html and a simple ping example: http://expect-lite.sourceforge.net/expect-lite_install.html, yet I couldn’t try it, I’m a bit busy with other duties, but I will try it soon...

Thanks for your interest Barrie!

[barriehie]

:) After -hours- of getting a 'segmentation fault' with trying to run inline assy to load the keyboard buffer I then thought of emulating the keyboard by using a socket. I don't know what your intent here is but to an application I'm figuring the 'name' of the device sending the data is probably irrelevant; only the receipt of the data is critical, so... I was thinking of falling back on sockets since I couldn't get anything else to work! :( I've got some client/server socket programs that I've gleaned from various places but they would have to be modified to work continuous. I've been meaning to understand those... :)

[barriehie]

Don't know what distro you're using but debian has a package

07:38:19 /home/barrie/programming/ $> aptitude search . | grep xvkbd
p   xvkbd                           - software virtual keyboard for X11
07:39:04 /home/barrie/programming/ $>

and startpage turned up this:
[url]http://scripts.top4download.com/kbde/ohiox.html[/url]

HTH

[emiliouy]

Thanks again Barrie, but I’ve tried with xvkbd before, and as you pasted here it’s part of the X11 scenery.

Finally, I've gotten some time to focus on the issue; I’ve found a simple way to do it, calling directly to the Unix sys API, inspired on Expect code and some other Google searches related to struct termio, ioctl call and so on...

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/file.h>
#include <termio.h>

#define STR_SIZE 256

static const char* EOL_CMD = "\n";
static const char* DEFAULT_CMD = "ls -l";

static bool SetEcho(int dev_tty, bool enable)
{
	struct termio termBuf;
	ioctl(dev_tty, TCGETA, &termBuf);
	if (enable) {
		termBuf.c_lflag |= ECHO; // Enable echo
	} else {
		termBuf.c_lflag &= ~ECHO; // Don't echo
	}
	ioctl(dev_tty, TCSETAW, &termBuf);
	return true;
}

static bool SendCMDToTTY(const char* cmd)
{
	int dev_tty = open("/dev/tty", O_RDWR);
	if (!dev_tty) {
		return false;
	}

	SetEcho(dev_tty, false);
	size_t cmdSize = strlen(cmd);
	for (size_t i = 0; i < cmdSize; i++) {
		ioctl(dev_tty, TIOCSTI, &cmd[i]);
	}
	SetEcho(dev_tty, true);

	close(dev_tty);
	return true;
}

int main(int argc, char* argv[])
{
	char sys_cmd[STR_SIZE];
	memset(sys_cmd, NULL, STR_SIZE);
	for (int i = 1; i < argc; i++) {
		sprintf(sys_cmd, "%s%s%s", sys_cmd, i == 1 ? "" : " ", argv[i]);
	}
	if (argc == 1) {
		sprintf(sys_cmd, "%s", DEFAULT_CMD);
	}
	sprintf(sys_cmd, "%s%s", sys_cmd, EOL_CMD);
	sys_cmd[STR_SIZE - 1] = NULL;

	if (!SendCMDToTTY(sys_cmd)) {
		perror("Error while sending the command to TTY");
	}
	return 0;
}

It’s just a basic example, and it has to be improved with some error checking on system calls, command arguments maybe, etc, etc... but I hope this may help someone else,

Regards,
e-milio.

[barriehie]

Glad you got it! I spent the better part of a day messing around with sockets in an attempt to 'emulate' this... :)