node.js fs.stat读取的文件长度为0

Question

谷歌找了一圈没找到答案，先贴代码：

const fs = require('fs')
fs.watch('./test.log', {}, (e) => {
  const stats = fs.statSync('./test.log') 
  console.log(stats.size)
})

当你不断往test.log文件添加文字，会先打出0再打出实际文件长度，如下所示

请问有谁知道是为什么么，求解释！！

补充一下：
运行代码后，我用编辑器打开test.log这个文件，手动的往里面写东西。这个会有影响么？

Answer 1

Print the information when the change occurs and take a look
See what operations the editor performs on the file. Accessing/modifying the file will trigger the file change event
Node writes the file and then monitors the file. Nothing appears as you said The problem is as follows:

var fs = require('fs');
var util=require('util');

fs.watch('./test.log', {}, function(e){
    var stats = fs.statSync('./test.log');
    console.log(util.inspect(stats));//打印发生变化时的信息
    console.log(stats.size)
});

var writeStream=fs.createWriteStream('./test.log', {
    flags: 'a+',
    defaultEncoding: 'utf8'
});

setInterval(function(){
    writeStream.write("a");
},1000);

Answer 2

I haven’t tried it, it’s probably because the file was occupied when you were adding text,

Answer 3

Just ctrl+s will be executed twice