Introduction to Child Process Promise

The child-process-promise library is a powerful and versatile tool for managing child processes in Node.js. It wraps the native child process module, making it promise-based, which simplifies dealing with asynchronous operations. This guide explores the rich set of APIs provided by child-process-promise, complete with code snippets, and a sample app to demonstrate its practical usage.

Installation

npm install child-process-promise

Basic Usage

  
const { exec, spawn } = require('child-process-promise');

exec('echo "Hello World"')
  .then((result) => {
    console.log(result.stdout);
  })
  .catch((err) => {
    console.error(err);
  });
  

Spawning a Child Process

  
const { spawn } = require('child-process-promise');

const promise = spawn('ls', ['-lha']);
const childProcess = promise.childProcess;

console.log('[spawn] childProcess.pid: ', childProcess.pid);
childProcess.stdout.on('data', (data) => {
  console.log('[spawn] stdout: ', data.toString());
});

promise
  .then(() => {
    console.log('[spawn] done!');
  })
  .catch((err) => {
    console.error('[spawn] ERROR: ', err);
  });
  

Using execFile

  
const { execFile } = require('child-process-promise');

execFile('node', ['--version'])
  .then((result) => {
    console.log('Node Version: ', result.stdout);
  })
  .catch((err) => {
    console.error('Error: ', err);
  });
  

Example Application

Below is an example application demonstrating how to use child-process-promise to manage different child processes.

  
const { exec, spawn } = require('child-process-promise');

const runCommands = async () => {
  try {
    // Execute an echo command
    let result = await exec('echo "Welcome to the Child Process Promise Example"');
    console.log(result.stdout);

    // List files in the current directory
    await spawn('ls', ['-lha'])
      .childProcess.stdout.on('data', (data) => {
        console.log('List of files: ', data.toString());
      });

    // Get current Node.js version
    result = await exec('node --version');
    console.log('Node.js Version: ', result.stdout);

  } catch (err) {
    console.error('Error occurred: ', err);
  }
};

runCommands();
  

With child-process-promise, handling child processes in Node.js becomes straightforward and efficient, greatly improving your application’s error handling and control flow.

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