Executing shell command using child_process in javascript

Question

Trying to execute shell command(any) from the browser and printing the result on the Ui using child_process.

unable to fetch the results from command line asynchronously.Am I missing something here ?

   const exec = require('child_process').exec;
    app.post('/plan',(req, res) => {

      let cmd = exec('dir');
      let output = "";
      cmd.stdout.on('data', (data) => {
        //console.log(`stderr: ${data}`);
        output += data;
       });
      res.send(output);                          //not working
      console.log(output);                       //its empty
      cmd.stderr.on('data', (data) => {
          console.log(`stderr: ${data}`);
       });
      cmd.on('close', (code) => {
         console.log(`child process exited with code ${code}`);
      });

    });

Lucas · Accepted Answer · 2018-12-05 01:52:22Z

1

The shell command runs asynchronously. You need to send the response from within the callback function so that it sends the result when it is finished executing.

  cmd.stdout.on('data', (data) => {
    output += data;
    res.send(output); 
   });

Might be cleaner to do it like this:

const exec = require('child_process').exec;
app.post('/plan',(req, res) => {
  exec('dir', (error, stdout, stderr) => {
    if (error) {
      res.status(500).send(stderr);
      return;
    }
    res.send(stdout);
  });
});

edited Dec 5, 2018 at 1:52

answered Dec 5, 2018 at 1:45

Lucas

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2 Comments

Hith Over a year ago

how do i access the stdout on ui ? the result which im recieving is

body: (...) bodyUsed: false headers: Headers {} ok: true redirected: false status: 200 statusText: "OK" type: "basic" url: "http://localhost:3000/plan" __proto__: Response

Lucas Over a year ago

You need to read the response stream as text developer.mozilla.org/en-US/docs/Web/API/Response. Try fetch('http://localhost:3000/plan').then(response => response.text()).then(console.log)

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