Nodejs: write to stdin of bash process crashes with EPIPE - node.js

Question

My node process gets some PDF file via HTTP Request, then uses the request's onData event to pass the incoming data on to a properly configured lpr, spawned via child_process.exec. I write to stdin using process.stdin.write(...), followed by process.stdin.end() when done. This allows me to print those files immediately.
Now I have a situation where I don't want the data to be piped to lpr, but to some bash script. The script uses cat to process its stdin.
myscript.sh < somefile.pdf works as expected, as does cat somefile.pdf | myscript.sh.
However, when I spawn /path/to/script.sh from node (by simply replacing lpr with the script path in the source), the process exits with
events.js:183
throw er; // Unhandled 'error' event
^
Error: write EPIPE
at WriteWrap.afterWrite [as oncomplete] (net.js:868:14)
Subsequently, the whole node process crashes, the error sneaking around all try...catch blocks. Logging at the beginning of the bash script shows, it does not even get started.
When I target anything that's not a shell script but some compiled executable, like cat, echo,... everything works just fine.
Adding epipebomb module would not change anything.
I also tried piping to process.exec("bash", ["-c cat | myscript.sh"]), with the same errors.
An example bash script, just to test for execution:
#!/usr/bin/env bash
date > logfile.txt
cat > /dev/null
EDIT:
I think I maybe need to signal to keep the stdin stream open somehow.
The process-spawning part of the script, leaving promisification and output processing away:
const process = require("child_process")
// inputObservable being an rxjs Observable
execstuff(inputObervable) {
const task = process.spawn("/path/to/script.sh");
inputObservable.subscribe(
chunk => task.stdin.write(chunk),
error => console.error(error),
finished => task.stdin.end()
);
}

Answer 1

There is an example at child_process.spawn how you can write the following lines ps ax | grep ssh as node.js script, maybe it will be helpful for you:
const { spawn } = require('child_process');
const ps = spawn('ps', ['ax']);
const grep = spawn('grep', ['ssh']);
ps.stdout.on('data', (data) => {
grep.stdin.write(data);
});
ps.stderr.on('data', (data) => {
console.log(`ps stderr: ${data}`);
});
The first impression is that you are doing the same stuff, the problem may be in the chunk data, maybe one of the chunks is null, and it is closing the stream, and you want to close it by running task.stdin.end().
The other thing you can try is to run the node.js script with the NODE_DEBUG=stream node script.js
Will log the node.js internals how the stream, behaves, also may be helpful for you.