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node.jsspawnpty

Pipe Node stdout in realtime

I have a spawn process running a docker pull and I'm using the following:

const proc = spawn('docker', [ 'pull', 'some/container' ], { env: process.env, cwd: process.env.HOME })
proc.stdout.pipe(process.stdout)

As it runs it breaks up and downloads the individual SHA's and the above works pretty well, however, it puts each response on a new line. I'm curious if there's a way to emulate the "normal" output so each line writes as it pull the image.

Solution

  • If you're just piping to process.stdout, then you could just set the stdio option like: 

    const proc = spawn('docker', [
  'pull',
  'some/container'
], {
  env: process.env,
  cwd: process.env.HOME,
  stdio: ['pipe', process.stdout, 'pipe']
});

    The end result being that docker will now see its stdout as a TTY (assuming this node script is being run from a terminal/pty of course) and not a pipe.