Node.js 中 Child Process 模块详解：创建、通信与生命周期管理

interface ChildProcess extends events.EventEmitter {
 stdin: Writable | null;
 stdout: Readable | null;
 stderr: Readable | null;
 readonly channel?: Pipe | null;
 readonly stdio: [
  Writable | null, // stdin
  Readable | null, // stdout
  Readable | null, // stderr
  Readable | Writable | null | undefined, // extra
  Readable | Writable | null | undefined // extra
 ];
 readonly killed: boolean;
 readonly pid: number;
 readonly connected: boolean;
 readonly exitCode: number | null;
 readonly signalCode: NodeJS.Signals | null;
 readonly spawnargs: string[];
 readonly spawnfile: string;
 kill(signal?: NodeJS.Signals | number): boolean;
 send(message: Serializable, callback?: (error: Error | null) => void): boolean;
 send(message: Serializable, sendHandle?: SendHandle, callback?: (error: Error | null) => void): boolean;
 send(message: Serializable, sendHandle?: SendHandle, options?: MessageOptions, callback?: (error: Error | null) => void): boolean;
 disconnect(): void;
 unref(): void;
 ref(): void;

 /**
  * events.EventEmitter
  * 1. close
  * 2. disconnect
  * 3. error
  * 4. exit
  * 5. message
  */
 ...
 }

const { spawn } = require('child_process');
const ls = spawn('ls', ['-lh', '/usr']);

ls.stdout.on('data', (data) => {
 console.log(`stdout: ${data}`);
});

ls.on('close', (code) => {
 console.log(`子进程使用代码 $[code] 关闭所有 stdio`);
});

ls.on('exit', (code) => {
 console.log(`子进程使用代码 $[code] 退出`);
});

const { spawn } = require('child_process');

const subprocess = spawn('ls');

subprocess.stdout.on('data', (data) => {
 console.log(`接收到数据块 ${data}`);
});

readonly stdio: [
  Writable | null, // stdin
  Readable | null, // stdout
  Readable | null, // stderr
  Readable | Writable | null | undefined, // extra
  Readable | Writable | null | undefined // extra
 ];

const assert = require('assert');
const fs = require('fs');
const child_process = require('child_process');

const subprocess = child_process.spawn('ls', {
 stdio: [
 0, // 使用父进程的 stdin 用于子进程。
 'pipe', // 把子进程的 stdout 通过管道传到父进程 。
 fs.openSync('err.out', 'w') // 把子进程的 stderr 定向到一个文件。
 ]
});

assert.strictEqual(subprocess.stdio[0], null);
assert.strictEqual(subprocess.stdio[0], subprocess.stdin);

assert(subprocess.stdout);
assert.strictEqual(subprocess.stdio[1], subprocess.stdout);

assert.strictEqual(subprocess.stdio[2], null);
assert.strictEqual(subprocess.stdio[2], subprocess.stderr);

const { spawn } = require('child_process');

const subprocess = spawn(process.argv[0], ['child_program.js'], {
 detached: true,
 stdio: 'ignore'
});

subprocess.unref();

subprocess.send(message[, sendHandle[, options]][, callback])

const subprocess = require('child_process').fork('subprocess.js');

// 打开 server 对象，并发送该句柄。
const server = require('net').createServer();
server.on('connection', (socket) => {
 socket.end('由父进程处理');
});
server.listen(1337, () => {
 subprocess.send('server', server);
});

process.on('message', (m, server) => {
 if (m === 'server') {
 server.on('connection', (socket) => {
 socket.end('由子进程处理');
 });
 }
});

onst { fork } = require('child_process');
const normal = fork('subprocess.js', ['normal']);
const special = fork('subprocess.js', ['special']);

// 开启 server，并发送 socket 给子进程。
// 使用 `pauseOnConnect` 防止 socket 在被发送到子进程之前被读取。
const server = require('net').createServer({ pauseOnConnect: true });
server.on('connection', (socket) => {

 // 特殊优先级。
 if (socket.remoteAddress === '74.125.127.100') {
 special.send('socket', socket);
 return;
 }
 // 普通优先级。
 normal.send('socket', socket);
});
server.listen(1337);

process.on('message', (m, socket) => {
 if (m === 'socket') {
 if (socket) {
 // 检查客户端 socket 是否存在。
 // socket 在被发送与被子进程接收这段时间内可被关闭。
 socket.end(`请求使用 ${process.argv[2]} 优先级处理`);
 }
 }
});

child_process.spawn(command[, args][, options])

child_process.fork(modulePath[, args][, options])

child_process.exec(command[, options][, callback])

child_process.execFile(file[, args][, options][, callback])

// 仅在 Windows 上。
const { spawn } = require('child_process');
const bat = spawn('cmd.exe', ['/c', 'my.bat']);

bat.stdout.on('data', (data) => {
 console.log(data.toString());
});

bat.stderr.on('data', (data) => {
 console.error(data.toString());
});

bat.on('exit', (code) => {
 console.log(`子进程退出，退出码 $[code]`);
});

const { exec, spawn } = require('child_process');
exec('my.bat', (err, stdout, stderr) => {
 if (err) {
 console.error(err);
 return;
 }
 console.log(stdout);
});

// 文件名中包含空格的脚本：
const bat = spawn('"my script.cmd"', ['a', 'b'], { shell: true });
// 或：
exec('"my script.cmd" a b', (err, stdout, stderr) => {
 // ...
});