如何在 Node.js 中的主进程和子进程之间传递流输入/输出

Question

我正在尝试让两个进程通过stdio 相互“对话”：

ping.js

import { readline } from '../readline';
import { sleep } from '../sleep';
import { spawn } from 'child_process';

const spawnPongProcess = () => {
    const child = spawn('node',
        ['-r', 'esm', `${__dirname}/pong.js`],
        { stdio: 'pipe' });

    child.stderr.on('data', (data) => {
        console.error(`stderr: ${data}`);
    });

    child.on('close', (code) => {
        console.error(`child process exited with code ${code}`);
        process.stdin.resume();
        process.stdout.resume();
    });

    child.on('error', (err) => {
        console.error(`child process error: ${err}`);
    });

    process.stdout.pipe(child.stdin);
    child.stdout.pipe(process.stdin);

    return child;
};

export const ping = async () => {
    const child = spawnPongProcess();

    await sleep(1000);

    console.log('ping');

    let pong = readline();

    console.error(`Ping received: ${pong}`);

    child.kill();
};

我通过管道将父进程 stdout 传递给子进程 stdin，并将子进程 stdout 传递给父进程 stdin，以允许进程通过 stdio 进行通信。

pong.js

import { readline } from '../readline';
import { sleep } from '../sleep';

const pong = async () => {

    console.log(`Pong initiated and waiting for input.`);

    let ping = readline();

    console.log(`Pong received: ${ping}`);

    process.exit();
};

pong();

readline.js

import { question } from 'readline-sync';

export const readline = question;

sleep.js

export const sleep = (ms) => {
    return new Promise((resolve) => setTimeout(resolve, ms));
};

输出是：

$ node -r esm src/index.js
Pong initiated and waiting for input.
ping

父进程 (ping) 的输出似乎没有传递到子进程 (pong)。关于如何使其工作的任何想法？

Answer 1

您将进程的stdout（可写）通过管道传输到子进程的stdin（可写），反之亦然。由于在stdin（可读）上接收到数据，因此您必须通过管道而不是stdout：

process.stdin.pipe(child.stdin);
child.stdout.pipe(process.stdout);

您的代码不会抛出异常，因为如果标准输出是终端，它就会变成双工流。