CODEWITHSUNDEEP
node.jswindowsoutputstreamchild-processspawn
Adcent
Adcent

Reputation: 11

Node.js Child process can not catch windows exe file's output

I want to use child_process.spawn to execute a windows exe file and catch it's output.

When I use command line to run a thirdparty exe file (says A.exe), it will print some logs to the cmd window. Like this:

C:\> A.exe
some outputs...
some more outputs...

However, when I spawn it in node.js, using this

import childProcess from 'child_process';

const cp = childProcess.spawn('A.exe');
cp.stdout.on('data', data => console.log(`stdout: ${data}`));
cp.stderr.on('data', data => console.log(`stderr: ${data}`));

There is no outputs at all.

I think the outputs of A.exe is not to the stdout (so I can never get data by listening stdout), but I don't know how it print logs when running from command line.

Any help would be greatly appreciated.

Upvotes: 1

Views: 4704

Answers (3)

Alonso Rodriguez
Alonso Rodriguez

Reputation: 1

I know this question is quite old, but im answering because it could help someone else.

I developed a .exe based on a Python program with PyInstaller. I wasnt able to get the Stdout of my .exe, even though i could see the prints on the .exe terminal.

After adding a stdout.flush() after every print(), and the rebuilding my .exe, i was able to get the data from the spawned subprocess on Nodejs.

Upvotes: 0

Suraj
Suraj

Reputation: 395

On Unix-type operating systems (Unix, Linux, macOS) child_process.execFile() can be more efficient because it does not spawn a shell. On Windows, however, .bat and .cmd files are not executable on their own without a terminal, and therefore cannot be launched using child_process.execFile(). When running on Windows, .bat and .cmd files can be invoked using child_process.spawn() with the shell option set, with child_process.exec(), or by spawning cmd.exe and passing the .bat or .cmd file as an argument (which is what the shell option and child_process.exec() do). In any case, if the script filename contains spaces it needs to be quoted.

// On Windows Only ...
const { spawn } = require('child_process');
const bat = spawn('cmd.exe', ['/c', 'my.bat']);

bat.stdout.on('data', (data) => {
  console.log(data.toString());
});

bat.stderr.on('data', (data) => {
  console.log(data.toString());
});

bat.on('exit', (code) => {
  console.log(`Child exited with code ${code}`);
});

Upvotes: 1

Terry Lennox
Terry Lennox

Reputation: 30725

Maybe give this approach a go:

var childProcess = require('child_process');
childProcess.exec('A.exe', function(error, stdout, stderr) {

    if (error != null) {
        console.log('error occurred: ' + error);
    } else {
        console.log('stdout: ' + stdout);
        console.log('stderr: ' + stderr);
    }
});

// OR
var cp = childProcess.spawn('A.exe');

cp.stdout.on('data', (data) => {
  console.log('stdout: ' + data.toString());
});

cp.stderr.on('data', (data) => {
  console.log('stderr: ' + data.toString());
});

Upvotes: 0

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