CODEWITHSUNDEEP
clinuxubuntukeyboard
user900360
user900360

Reputation:

Access Keystrokes in C

I am trying to access keystrokes in C. I can access alphanumeric keys. How can I access Control, Shift and Alt key?
Plus I read somewhere that sometimes while entering text in console, OS masks backspace key. I would like to know where user pressed backspace key. It's not same as knowing when '\n' was pressed. GNU C. Ubuntu 11.

Upvotes: 1

Views: 4031

Answers (3)

Georgegoldman
Georgegoldman

Reputation: 173

here is a correct solution with c without any lib

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/input.h>

int main() {
    int fd;
    struct input_event ev;

    // Open the input device file
    fd = open("/dev/input/event0", O_RDONLY);
    if (fd == -1) {
        perror("Error opening input device");
        return 1;
    }

    while (1) {
        // Read the next input event
        if (read(fd, &ev, sizeof(struct input_event)) == sizeof(struct input_event)) {
            // Check if the event is a key press
            if (ev.type == EV_KEY && ev.value == 1) {
                printf("Key pressed: %d\n", ev.code);
                if (ev.code == KEY_Q) // Check if 'q' key is pressed
                    break;
            }
        }
    }

    // Close the input device file
    close(fd);

    return 0;
}

so you occasionally need to change the value at eventx where x = integer, to get you keybaord event you change it and recompiled until that for your keyboard.

Upvotes: 0

jforberg
jforberg

Reputation: 6752

The simple answer is "you can't", at least not easily or without downloading third party libraries.

Most C programs shouldn't have to know anything about the keyboard or the screen. Standard C is only concerned with reading from and writing to files (the keyboard and screen being special-case files).

Assuming you have a good reason for wanting to access the keyboard directly, you should be looking at the ncurses library (http://www.gnu.org/software/ncurses/ncurses.html). Ncurses knows how many different (virtual) terminals and keyboards work, and it presents a uniform interface to them. It lets you paint the screen and create a substitute graphical interface using only blocks of text.

Since you use Ubuntu, try running the "aptitude" command to see a good example of what ncurses can do.

Upvotes: 1

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

Dietrich Epp answered in a comment: use ncurses library.

See also this question

And you might make an X11 client graphical application; in that case use a graphical toolkit library like GTK or Qt

If you want to make a console application, use ncurses or perhaps readline

And your question, when taken literally, has no sense: the strict C standard don't know what a key or a keystroke is (the only I/O operations mentioned in the standard are related to <stdio.h> thru FILE). This is why most people uses additional libraries and standards (in addition of those required by ISO C), eg. Posix...

Upvotes: 2

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