Process

Process Properties

• process.pid: 当前进程的进程号.
• process.version: Node 的版本, 比如 v0.10.18.
• process.platform: 当前系统平台, 比如 Linux.
• process.title: 默认值为“node”, 可以自定义该值.
• process.argv: 当前进程的命令行参数数组.
• process.env: 指向当前 shell 的环境变量, 比如 process.env.HOME.
• process.execPath: 运行当前进程的可执行文件的绝对路径.
• process.stdout: 指向标准输出.
• process.stdin: 指向标准输入.
• process.stderr: 指向标准错误.

process.stdin.resume()
process.stdin.pipe(process.stdout)

Process Events

• Error events:
  • uncaughtException.
  • unhandledRejection.
• Signal events:
  • SIGHUP.
  • SIGINT.
  • SIGQUIT.
  • SIGTERM.
• Exit events:
  • beforeExit.
  • exit.
• Node HTTP applications graceful shutdown library.

process.on('uncaughtException', (err) => {
  console.log(`Uncaught exception: ${err.message}.`)
  process.exit(1)
})
process.on('uncaughtException', (reason, promise) => {
  console.log(`Unhandled rejection at ${promise}, reason: ${reason}.`)
  process.exit(1)
})

process.on('SIGHUP', (signal) => {
  console.log(`Process ${process.pid} received a SIGHUP signal.`)
  process.exit(0)
})
process.on('SIGINT', (signal) => {
  console.log(`Process ${process.pid} has been interrupted.`)
  process.exit(0)
})
process.on('SIGQUIT', (signal) => {
  console.log(`Process ${process.pid} received a SIGQUIT signal.`)
  process.exit(0)
})
process.on('SIGTERM', (signal) => {
  console.log(`Process ${process.pid} received a SIGTERM signal.`)
  process.exit(0)
})

process.on('beforeExit', (code) => {
  setTimeout(() => {
    console.log(`Process will exit with code: ${code}.`)
    process.exit(code)
  })
})
process.on('exit', (code) => {
  console.log(`Process exited with code: ${code}.`)
})

Process Information

• process.on()
• process.uptime(): 进程运行时长
• process.getgid/setgid/getuid/setuid();
• process.cwd()
• process.memoryUsage()

Process Event Loop and Counter

• process.nextTick()

Child Process

• cp.spawn(): 创建子进程, 拥有独立的 stdin/stdout/stderr 文件描述符
• cp.exec(): 创建子进程, 并会在进程结束时调用传入的回调函数
• Exec Library
• Each spawned Node.js child process is independent and has its own memory, event-loop, and V8 instance.
• Use process.on to communicate between parent and child process.

const cp = require('node:child_process')

cp.exec(
  'ls -l',
  {
    encoding: 'uft-8',
    timeout: 0,
    maxBuffer: 200 * 1024,
    killSignal: 'SIGTERM',
    setsid: false,
    cwd: null,
    env: null,
  },
  (err, stdout, stderr) => {
    if (!err) {
      console.log(stdout)
      console.log(stderr)
    }
  }
)