Question

我有这段代码

const express = require('express')
const app = express()

app.get('/', function (req, res) {
    var process = require('child_process');
    process.exec('hadoop fs -ls',function (err,stdout,stderr) {
        if (err) {
            console.log(typeof(stderr));
            console.log("\n"+stderr);
            res.send(stderr);
        } else {
            console.log(stdout);
        }
    });
    res.send('Hello World!')
})

app.listen(3000, function () {
    console.log('Example app listening on port 3000!')
})

我希望它可以将cmd输出发送回客户端，但是我收到了这个错误：

C:\Users\Administrator\Desktop\CSSE 434\project\backend>node index.js
Example app listening on port 3000!
string

'hadoop' is not recognized as an internal or external command,
operable program or batch file.

_http_outgoing.js:371
    throw new Error('Can\'t set headers after they are sent.');
    ^

Error: Can't set headers after they are sent.
    at ServerResponse.setHeader (_http_outgoing.js:371:11)
    at ServerResponse.header (C:\Users\Administrator\Desktop\CSSE434\project\backend\node_modules\express\lib\response.js:767:10)
    at ServerResponse.contentType (C:\Users\Administrator\Desktop\CSSE 434\project\backend\node_modules\express\lib\response.js:595:15)
    at ServerResponse.send (C:\Users\Administrator\Desktop\CSSE 434\project\backend\node_modules\express\lib\response.js:145:14)
    at C:\Users\Administrator\Desktop\CSSE434\project\backend\index.js:10:17
    at ChildProcess.exithandler (child_process.js:212:5)
   at emitTwo (events.js:106:13)
    at ChildProcess.emit (events.js:194:7)
    at maybeClose (internal/child_process.js:899:16)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:226:5)

如您所见，输出string表明stderr是一个字符串类型 hadoop is not recognized是正常的，因为我本地没有hadoop 但我无法弄清楚为什么它不会将结果发送给我的客户。有人可以帮我这个吗？

PS：这是我项目中唯一的文件。没有其他文件可供展示

Answer 1

好吧，我只需要返回res.send（stderr）;当它试图发送＆＃34; hello world＆＃34;时会发生错误。发送stderr后

使用node和express发送stdout / stderr

1 个答案: