javascript - Node.js 文件观看基本示例

Question

我正在读一本名为“Node.js the right way”的书。

书中的示例代码之一是我们观察文件“text.txt”的变化。

node.js代码如下:

const fs = require('fs');
var filename = process.argv[2];
console.log(filename);
var count = 0;
if (!filename) {
   throw Error("A file to watch must be specified!");
} else {
   console.log(filename);
}

fs.watch(filename, function() {
   count = count + 1;
   console.log("File 'text.txt' has been changed ("+count+") times!");
});

console.log("Now watching " + filename + " for changes...");

书上说终端命令应该是这样的:

$ node --harmony watcher.js text.txt

但是，这失败了，并给出了以下错误:

fs.js:1237
    throw errnoException(err, 'watch');
    ^
Error: watch ENOENT
    at exports._errnoException (util.js:837:11)
    at FSWatcher.start (fs.js:1237:11)
    at Object.fs.watch (fs.js:1263:11)
    at Object.<anonymous> (/home/ubuntu/workspace/watcher.js:12:4)
    at Module._compile (module.js:434:26)
    at Object.Module._extensions..js (module.js:452:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Function.Module.runMain (module.js:475:10)
    at startup (node.js:117:18)

除非我像这样输入完整的目标文件路径:

$ node --harmony watcher.js /home/ubuntu/workspace/text.txt

哪个是正确的？为什么它识别“watcher.js”文件而不是 text.txt 文件，尽管它们都在同一目录中？我怎样才能克服这个问题并在命令行中输入“text.txt”？

Answer 1

您应该在系统中解析该文件。试试这个命令:

node --harmony watcher.js ./text.txt

您可以修复您的代码:

const fs = require('fs');
const path = require('path');
var filename = process.argv[2];
if(!path.isAbsolute(filename)){
    filename = path.join(__dirname, filename);
}
console.log(filename);