使用节点和快递发送 stdout/stderr

Question

我有这个代码

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，但我收到此错误：

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)

可以看到，输出string表明stderr是字符串类型 hadoop is not recognized 是正常的，因为我本地没有 hadoop 但我就是不明白为什么它不将结果发送给我的客户。有人可以帮我解决这个问题吗？

PS:这是我的唯一文件project.There没有其他文件显示

Answer 1

好吧，我只需要 return res.send(stderr);发送 stderr

后尝试发送 "hello world" 时发生错误

使用节点和快递发送 stdout/stderr

send stdout/stderr using node and express

child-process

node.js

express