如何使用输入子系统生成击键事件

我正在Linux中编写一个键盘模拟器程序，作为一个开始，我能够在X11窗口中渲染按键，但这在虚拟终端中不工作，并尝试不同的方式。我参考http://thiemonge.org/getting-started-with-uinput并尝试使用uinput内核模块。根据教程中的按键可以作为uinput事件注入，我相应地编写了下面的代码:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <iostream>
#include <time.h>
#include <string>
#define die(str, args...) do { 
perror(str); 
exit(EXIT_FAILURE); 
} while(0)
int main(void)
{
    int                    fd_keyEmulator;
    struct uinput_user_dev uidev;
    struct input_event     ev;
    int                    dx, dy;
    int                    i;
    fd_keyEmulator = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if(fd_keyEmulator < 0)
    {
        std::cout << "error: open : " <<  strerror(errno) << std::endl;
    }
    int ret;
    //ret = ioctl(fd_keyEmulator, UI_SET_EVBIT, EV_KEY);
    //ret = ioctl(fd_keyEmulator, UI_SET_KEYBIT, KEY_D);
    //ret = ioctl(fd_keyEmulator, UI_SET_EVBIT, EV_SYN);
    sleep(5);
    if (ioctl(fd_keyEmulator, UI_SET_EVBIT, EV_KEY) < 0)
    {
        std::cout << "test 1 ..." << std::endl;
        die("error: ioctl");
    }
    if (ioctl(fd_keyEmulator, UI_SET_KEYBIT, KEY_D) < 0)
    {
        std::cout << "test 2 ..." << std::endl;
        die("error: ioctl");
    }
    if (ioctl(fd_keyEmulator, UI_SET_EVBIT, EV_REL) < 0)
    {
        std::cout << "test 3 ..." << std::endl;
        die("error: ioctl");
    }

    memset(&uidev, 0, sizeof(uidev));
    snprintf(uidev.name, UINPUT_MAX_NAME_SIZE, "keyboard-emulator");
    uidev.id.bustype = BUS_USB;
    uidev.id.vendor  = 0x1;
    uidev.id.product = 0x1;
    uidev.id.version = 1;
    std::cout << "Writing key press..." << std::endl;
    if(write(fd_keyEmulator, &uidev, sizeof(uidev)) < 0)
        std::cout << "error: write" <<  strerror(errno) << std::endl;
    if(ioctl(fd_keyEmulator, UI_DEV_CREATE) < 0)
        std::cout << "error: ioctl" <<  strerror(errno) << std::endl;

    memset(&ev, 0, sizeof(ev));
    ev.type = EV_REL;
    ev.code = KEY_D;
    ev.value = 1;
    //ret = write(fd_keyEmulator, &ev, sizeof(ev));
    if (write(fd_keyEmulator, &ev, sizeof (struct input_event)) < 0)
                die("error: write");
    if (write(fd_keyEmulator, &ev, sizeof (struct input_event)) < 0)
                die("error: write");
    if (write(fd_keyEmulator, &ev, sizeof (struct input_event)) < 0)
                die("error: write");
    if (write(fd_keyEmulator, &ev, sizeof (struct input_event)) < 0)
                die("error: write");

    if(ioctl(fd_keyEmulator, UI_DEV_DESTROY) < 0)
        std::cout << "error: ioctl" <<  strerror(errno) << std::endl;
    close(fd_keyEmulator);
}

在这种情况下，我正在尝试的是为按键'd'生成一个uinput事件。但是随着程序的执行，我什么也看不见。有人能帮我验证一下这个程序吗?在教程中也不清楚如何使用uinput子系统注入按键。

编辑:我写了一个不同的程序，但是我看不到任何输出。我迷路了，请帮助我，谢谢。

#include <cstdlib>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <iostream>
#include <time.h>
#include <string>
using namespace std;
/*
 * 
 */
int main(int argc, char** argv) {
    // create uinput file descriptor
    int fd_key_emulator;                                                                    
    // open file descriptor
    fd_key_emulator = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if(fd_key_emulator < 0)
    {
        std::cout << "error in open : " << strerror(errno) << std::endl;
    }
    // uinput_user_dev struct for fake keyboard
    struct uinput_user_dev dev_fake_keyboard;
    memset(&dev_fake_keyboard, 0, sizeof(uinput_user_dev));
    snprintf(dev_fake_keyboard.name, UINPUT_MAX_NAME_SIZE, "kb-emulator");
    dev_fake_keyboard.id.bustype = BUS_USB;
    dev_fake_keyboard.id.vendor = 0x01;
    dev_fake_keyboard.id.product = 0x01;
    dev_fake_keyboard.id.version = 1;

    /**configure the input device to send type of events, inform to subsystem which 
     * type of input events we are using via ioctl calls. 
     * UI_SET_EVBIT ioctl request is used to applied on uinput descriptor to enable a type of event.
     **/
    // enable key press/release event
    if(ioctl(fd_key_emulator, UI_SET_EVBIT, EV_KEY))
    {
        std::cout << "Error in ioctl : UI_SET_EVBIT : EV_KEY : " << strerror(errno) << std::endl;
    }
    // enable set of KEY events here
    if(ioctl(fd_key_emulator, UI_SET_KEYBIT, KEY_A))
    {
        std::cout << "Error in ioctl : UI_SET_KEYBIT : KEY_A : " << strerror(errno) << std::endl;
    }
    // enable synchronization event
    if(ioctl(fd_key_emulator, UI_SET_EVBIT, EV_SYN))
    {
        std::cout << "Error in ioctl : UI_SET_EVBIT : EV_SYN : " << strerror(errno) << std::endl;
    }
    // now write the uinput_user_dev structure into uinput file descriptor
    if(write(fd_key_emulator, &dev_fake_keyboard, sizeof(uinput_user_dev)) < 0)
    {
        std::cout << "Error in write(): uinput_user_dev struct into uinput file descriptor: " << strerror(errno) << std::endl;
    }
    // create the device via an IOCTL call 
    if(ioctl(fd_key_emulator, UI_DEV_CREATE))
    {
        std::cout << "Error in ioctl : UI_DEV_CREATE : " << strerror(errno) << std::endl;
    }
    // now fd_key_emulator represents the end-point file descriptor of the new input device. 

    // struct member for input events
    struct input_event key_input_event;
    memset(&key_input_event, 0, sizeof(input_event));
    // key press event for 'a'
    key_input_event.type = EV_KEY;
    key_input_event.code = KEY_A;
    key_input_event.value = 1;
    // now write to the file descriptor
    if(write(fd_key_emulator, &key_input_event, sizeof(input_event)) < 0)
    {
        std::cout << "Error write : KEY_A press : " << strerror(errno) << std::endl;
    }
    memset(&key_input_event, 0, sizeof(input_event));
    // EV_SYN for key press event
    key_input_event.type = EV_SYN;
    key_input_event.code = SYN_REPORT;
    key_input_event.value = 0;
    // now write to the file descriptor
    if(write(fd_key_emulator, &key_input_event, sizeof(input_event)) < 0)
    {
        std::cout << "Error write : EV_SYN for key press : " << strerror(errno) << std::endl;
    }
    memset(&key_input_event, 0, sizeof(input_event));
    // key release event for 'a'
    key_input_event.type = EV_KEY;
    key_input_event.code = KEY_A;
    key_input_event.value = 0;
    // now write to the file descriptor
    if(write(fd_key_emulator, &key_input_event, sizeof(input_event)) < 0)
    {
        std::cout << "Error write : KEY_A release : " << strerror(errno) << std::endl;
    }
    memset(&key_input_event, 0, sizeof(input_event));
    // EV_SYN for key press event
    key_input_event.type = EV_SYN;
    key_input_event.code = SYN_REPORT;
    key_input_event.value = 0;
    // now write to the file descriptor
    if(write(fd_key_emulator, &key_input_event, sizeof(input_event)) < 0)
    {
        std::cout << "Error write : EV_SYN for key release : " << strerror(errno) << std::endl;
    }
    return 0;
}