How to use Node.js to modify the system time

Node.js is a JavaScript runtime environment with powerful server-side development capabilities. Modifying the system time is a problem often encountered in development, so in this article, we will explore how to use Node.js to modify the system time to help developers better complete the need to control the system time.

1. The principle of Node.js modifying the system time

We know that the system time is maintained by the real-time clock (RTC) on the computer hardware, and the modification of the system time is actually a modification RTC time on computer hardware. Node.js provides a NAPI interface that can modify the RTC time by accessing the underlying computer hardware.

Specifically, Node.js uses IOCTL (Input/Output Control) system calls to access computer hardware, and also provides some C-related extension libraries to assist in access.

2. Specific implementation of Node.js modifying the system time

1. Installing related libraries

Before you start using Node.js to modify the system time, you need to Install the relevant libraries first. On a Linux system, you can install it through the following command:

sudo apt-get install build-essential libudev-dev libusb-1.0-0-dev

On a Windows system, you need to install Python 2.7 first and configure the environment variables. Then run the following command in the Windows command line:

npm install node-hid

2. Access hardware interface

After installing the relevant libraries, we can start accessing the underlying hardware interface. Accessing hardware interfaces in Node.js requires the use of C extension libraries. Here we use the node-hid library to access USB HID devices.

// 引入 node-hid 库
const HID = require('node-hid');

// 通过 VID 和 PID 查找 USB 设备
const devices = HID.devices().filter(device => device.vendorId === 0x0483
  && device.productId === 0x5730);

// 获取设备句柄
const device = new HID.HID(devices[0].path);

In the above code, we first introduced the node-hid library, then obtained all USB device information through the HID.devices() method, and used filtering The conditions found the equipment we needed. Finally, use the new HID.HID(path) method to obtain the device handle.

3. Modify RTC time

After we have the device handle, we can start modifying the RTC time. The following is the specific implementation:

// 将当前时间转换成 16 进制
function getCurrentTimeHexString() {
  const date = new Date();

  // 将时间转换成秒
  const seconds = date.getSeconds()
    + date.getMinutes() * 60
    + date.getHours() * 3600;

  // 获取当前日期与 2001 年 1 月 1 日的相对天数
  const totalDays = Math.floor(
    (Date.now() - new Date('2001-01-01T00:00:00.000Z')) / 86400000
  );

  // 将相对天数转换成 16 进制
  const daysHexString = ('0000' + totalDays.toString(16)).slice(-4);

  // 将秒数转换成 16 进制
  const secondsHexString = ('000000' + seconds.toString(16)).slice(-6);

  return daysHexString + secondsHexString;
}

// 设置 RTC 时间
function setRtcTime(device, timeHexString) {
  // 构造命令
  const command = Uint8Array.of(0x00, 0x81, 0x01, 0x00, 0x00, 0x51, 0x08);
  const timeArray = [];
  for (let i = 0; i < timeHexString.length; i += 2) {
    timeArray.push(parseInt(timeHexString.slice(i, i + 2), 16));
  }
  command.push(...timeArray);

  // 发送命令
  device.write(command);
}

In the above code, we define two methods: getCurrentTimeHexString() and setRtcTime(device, timeHexString). The former is used to set the current The time is converted into a hexadecimal string, and the latter is used to write the hexadecimal string into the RTC.

4. Set system time

After the above steps, we have successfully modified the RTC time, but the system does not take effect immediately. We still need to manually synchronize the RTC time to the system in time. The following is the specific implementation:

// 同步 RTC 时间到系统时间中
function syncSystemTime() {
  // 获取当前 RTC 时间
  const timeHexString = getCurrentTimeHexString();

  // 设置 RTC 时间
  setRtcTime(device, timeHexString);

  // 同步 RTC 时间到系统时间中
  exec('sudo hwclock --hctosys', (err) => {
    if (err) {
      console.error(`同步 RTC 时间到系统时间失败，错误信息：${err}`);
    } else {
      console.log('同步 RTC 时间到系统时间成功！');
    }
  });
}

In the above code, we use the sudo hwclock --hctosys command to synchronize the RTC time to the system time. At the same time, it should be noted that this command needs to be run with administrator privileges.

3. Summary

Through the introduction of this article, we understand the principle and specific implementation method of Node.js modifying the system time. Of course, using Node.js to modify the system time requires certain knowledge of computer operating systems and special hardware support. Therefore, it is only used for development and debugging in specific scenarios and must not be abused.

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