How to pipe text into command with promisified node exec - node.js

Question

I am using node to execute a jar file that usually takes a CSV file as an input path.
I would like to try and circumvent writing the CSV file and pipe in the CSV as a string into the process if possible.
I have this working with execSync but I would prever to use exec wrapped with promisify
The problem is that exec does not have the input option like execSync so I can't pipe data into it. How do you get around this? Or is the best practice to wrap execSync in a Promise?
import {execSync} from 'child_process';
export const runJar = async (input: string, cwd: string) => {
const out = execSync(`java -jar model.jar`, {
cwd,
input,
})
return out.toString('utf-8');
};

Answer 1

Minimalistic example usage of a childs process stdio.
https://nodejs.org/dist/latest-v14.x/docs/api/child_process.html#child_process_child_process_exec_command_options_callback
const child_process = require("child_process");
const fs = require("fs");
// exec returns a child process instance
// https://nodejs.org/dist/latest-v14.x/docs/api/child_process.html#child_process_class_childprocess
const child = child_process.exec("cat");
// write to child process stdin
child.stdin.write("Hello World");
// to read/parse your csv file
//fs.createReadStream("./file.csv").pipe(child.stdin);
// listen on child process stdout
child.stdout.on("data", (chunk) => {
console.log(chunk);
child.kill();
});
To promisfy this, you can listen on the exit (status) on the child process and resolve or reject the promise based on the exit code:
child.on("close", (code) => {
if (code != 0) {
reject();
} else {
resolve();
}
});
Example given:
const readParseCSV = function (file = "./file.csv") {
return new Promise((resolve, reject) => {
const child = child_process.exec("java -jar model.jar");
fs.createReadStream(file).pipe(child.stdin);
let response = "";
// listen on child process stdout
child.stdout.on("data", (chunk) => {
response += chunk;
});
child.on("close", (code) => {
if (code != 0) {
reject();
} else {
resolve(response);
}
});
});
};
Im not sure if this works on windows the same way as on linux.