从 node.js 检测文件内容更改 [英] Detect file content changes from node.js

问题描述

我使用 chokidar

require('chokidar').watch('./target.txt', {}).on('all', function(event, path) {
  console.log(event, path);
}).on('ready', function() {
  console.log('ready');
});

每次我重新保存文件时，即使没有更改，它也会导致 change 事件.有没有办法仅在实际内容已更改时才触发此事件?

It causes change event every time when I re-save file even without changes. Is there a way to make this fire events only if actual content has been changed?

推荐答案

您可以使用 add 和 change 上提供的 stats 参数.这仅适用于文件大小的更改，这对于绝大多数情况来说应该足够了.

You can use the stats parameter delivered on add and change. This will only work for changes on the size of the file, which should be enough for the vast majority of cases.

   var watchSize = 0;

    require('chokidar').watch('./target.txt', {}).on('all', function(event, path, stats) {  

        if(stats && stats.size != watchSize) {
            watchSize = stats.size;
            console.log(event);
        }
    }).on('ready', function(path, stats) {
      console.log('ready');
    });

如果剩下的少数情况确实与您的案例相关并且您没有性能问题，您可以使用这样的方法(遵循评论中的建议):

If the few remaining situations are indeed relevant for your case and you have no performance concerns, you can use something like this (following the suggestion in the comments):

var crypto   = require("crypto");
var fs       = require("fs");
var chokidar = require("chokidar");

watchFile("./target.txt");

//----------------------------------------------------
function watchFile(filePath){

    var watchHash;

    chokidar.watch(filePath, {}).on("all", function(event, path, stats) {

        if (event == "add" || event == "change"){

            getHash(filePath, function(hash){
                if (hash != watchHash){
                    watchHash = hash;
                    console.log(event);
                }
            });
        }
    });
}

//----------------------------------------------------
function getHash(filePath, callback){

    var stream = fs.ReadStream(filePath);   
    var md5sum = crypto.createHash("md5");

    stream.on("data", function(data) {
        md5sum.update(data);
    });

    stream.on("end", function() {
        callback(md5sum.digest("hex"));
    });
}

不过，这似乎有点多.

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