Track keyboard and mouse events in C on linux - c

Question

How can I track the keyboard or mouse events in Linux, in C?
Like for example if the user presses ESC Shift etc. I should be able to track it. Same way for the mouse. If the user moves the mouse or clicks left or right.
The implementation idea is to create a small screen saver with timer and I am struggling how to track the keyboard or mouse events to reset the timer.

Answer 1

One possibility is to use the Input Subsystem.
Take a look at this article: Using the Input Subsystem (http://www.linuxjournal.com/article/6429)
Another one is to create a working thread that try to read the file /dev/input/event* like e.g. here for keyboard:
// (const char *)ptr - pass your device like "/dev/input/event2" here
fd = open((const char *)ptr, O_RDONLY);
if (fd < 0)
{
fprintf(stderr, "failed to open input device %s: %s\n", (const char *)ptr, strerror(errno));
return NULL;
}
struct timeval escapeDown = { 0, 0};
int code;
while (1)
{
if (read(fd, &ev, sizeof(struct input_event)) < 0)
{
fprintf(stderr, "failed to read input event from input device %s: %s\n", (const char *)ptr, strerror(errno));
if (errno == EINTR)
continue;
break;
}
code = -1;
if (ev.type == EV_KEY)
{
switch (ev.code)
{
case eEsc:
if (ev.value == 1)
{
escapeDown = ev.time;
printf("DOWN: ESC\n");
}
else if (ev.value == 0 && escapeDown.tv_sec)
{
printf("UP: ESC\n");
if (isLongPressed(&escapeDown, &ev.time))
code = eEscLong;
else
code = eEsc;
escapeDown.tv_sec = 0;
escapeDown.tv_usec = 0;
}
break;
case eOk:
case eUp:
case eRight:
case eLeft:
case eDown:
if (ev.value == 0)
{
printf("UP: %s\n", keyName(ev.code));
code = ev.code;
}
else if (ev.value == 1)
{
printf("DOWN: %s\n", keyName(ev.code));
}
escapeDown.tv_sec = 0;
escapeDown.tv_usec = 0;
break;
default:
break;
}
}
if (code > 0)
{
struct sMsg* pMsg = malloc(sizeof(struct sMsg));
if (pMsg)
{
pMsg->nMsgType = eMsgKeyLogger;
pMsg->nIntValue= code;
postMsg(pMsg);
}
printf("generated keyboard event: %u %s\n",
code,
keyName(code));
}
else
usleep(100);
}
close(fd);

Answer 2

Considering the size and nature of your project, you might want to have a look at GLUT. It is actually a convenience library for OpenGL, but also provides easy-to-use cross-platform input handling and timer functionality. Just in case that you want to move to other platforms in the future. Other than that, it blends in well with the graphical nature of your application.
Edit: The project I linked is actually a successor to the original GLUT with an overall enhanced API. For the original API reference, look here.
In your case, you could use something like:
void keyboardFunc(unsigned char key, int x, int y)
{
switch (key)
{
case 'a':
break;
/* etc */
}
}
void displayFunc()
{
/* Statements issuing the drawing of your screensaver */
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
/* Other initialization code */
glutKeyboardFunc(keyboardFunc);
glutDisplayFunc(displayFunc);
glutMainLoop();
}