CODEWITHSUNDEEP
node.jsstdoutstdinchild-processstdio
santcleep
santcleep

Reputation: 13

Capturing the *complete* output stream of a child_process in NodeJS

I've been trying to capture the output of a child_process for a while now. The following code example is my current attempt.

Code:

// Spawning a shell
var terminal = require('child_process').spawn(`sh`, [], { stdio: [ 'inherit', 'pipe', 'inherit'] });
console.log("Shell spawned!");

terminal.stdout.on('data', (data) => {
  console.log(`Received chunk ${data}`);
});

Output:

Shell spawned!

Expected output:

Shell spawned!

$

When using 'inherit' instead of 'pipe' on the stdout option, I get the expected output. But since I need to capture the output of the process/shell, 'inherit' has no use to me. My question now is, how can I capture the whole output of the process's stdout stream and what is 'inherit' exactly doing? I tried to capture the process.stdout after using 'inherit'- obviously with no luck.

Upvotes: 1

Views: 2279

Answers (1)

kevintechie
kevintechie

Reputation: 1521

It is not possible to show the prompt from a child process shell because bash (and I assume other shells) don't output the prompt to stdout. See this post for details.

You can simulate it by writing to standard out instead of console.log().

const term = require('child_process')
  .spawn('sh', [], { stdio: [ 'inherit', 'pipe', 'pipe'] });

process.stdout.write('$ ');

term.stdout.on('data', (data) => {
  process.stdout.write(`\n${data}$ `);
});

term.stderr.on('data', (data) => {
  process.stderr.write(`\n${data}$ `);
});

Upvotes: 0

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