When using child_process.spawn in Node, it spawns a child process and automatically create stdin, stdout and stderr streams to interact with the child.
const child = require('child_process');
const subProcess = child.spawn("python", ["myPythonScript.py"])
subProcess.stdout.on('data', function(data) {
console.log('stdout: ' + data);
});
I thus imlemented this in my project but the thing is that the subprocess actually write on the output stream only when the buffer reach a certain size. And not when the buffer is set with data (whatever the size of the data). Indeed, i'd like to receive the subprocess output stream directly when it writes it on the output stream, and not when it has filled the whole buffer. any solution ?
EDIT: As pointed out by t.888, it should actually be working as i expect. And it actually does if I spawn another subprocess. A c++ one this time. But I don't know why it does not work when I spawn my python script. Actually, the python script sends only big chunks of messages via stdout (probably when the buffer is full)
I solved my problem yesterday. It was actually due to python itself and not child_process function.
I have to do
const subProcess = child.spawn("python", ["-u", "myPythonScript.py"])
instead of
const subProcess = child.spawn("python", ["myPythonScript.py"])
indeed, -u argument tells python to flush data as soon as possible.