spawn-sync

What is spawn-sync?

The spawn-sync npm package provides synchronous versions of Node.js's child_process.spawn and child_process.spawnSync functions. It allows you to execute shell commands and scripts synchronously, which can be useful in scenarios where you need to ensure that a command has completed before proceeding with the next step in your code.

What are spawn-sync's main functionalities?

Synchronous Command Execution

This feature allows you to execute shell commands synchronously. In this example, the 'ls -lh /usr' command is executed, and the output is printed to the console.

const spawnSync = require('spawn-sync');
const result = spawnSync('ls', ['-lh', '/usr']);
console.log(result.stdout.toString());

Handling Command Output

This feature allows you to handle the output of the executed command. In this example, the 'node -v' command is executed to get the Node.js version, and the output is printed to the console. If there's an error, it is logged to the console.

const spawnSync = require('spawn-sync');
const result = spawnSync('node', ['-v']);
if (result.error) {
  console.error('Error:', result.error);
} else {
  console.log('Node version:', result.stdout.toString());
}

Passing Environment Variables

This feature allows you to pass custom environment variables to the executed command. In this example, the 'printenv' command is executed with a custom environment variable 'CUSTOM_VAR' set to 'HelloWorld'. The output is printed to the console.

const spawnSync = require('spawn-sync');
const result = spawnSync('printenv', [], { env: { ...process.env, CUSTOM_VAR: 'HelloWorld' } });
console.log(result.stdout.toString());

Other packages similar to spawn-sync

child_process

The child_process module is a core Node.js module that provides the ability to spawn child processes. It includes both asynchronous and synchronous methods (spawn, exec, execFile, fork, and their synchronous counterparts). Unlike spawn-sync, child_process is built into Node.js and does not require an additional package installation.

execa

Execa is a modern alternative to the child_process module. It provides a more user-friendly API for executing shell commands and scripts. Execa supports both asynchronous and synchronous execution, similar to spawn-sync, but offers additional features like improved error handling and promise support.

shelljs

ShellJS is a portable (Windows/Linux/macOS) implementation of Unix shell commands on Node.js. It provides a synchronous API for executing shell commands, similar to spawn-sync. ShellJS is designed to be more cross-platform and user-friendly, making it a good alternative for scripting tasks.

README

spawn-sync

Polyfill for child_process.spawnSync.

On iojs and node >= 0.12 it will just export the built in child_process.spawnSync. On platforms that support compiling native modules it uses the thread-sleep module to wait for an output file to exist in a tight loop. In this way it gains excellent cross platform support, but don't expect it to be efficient on all platforms.

Installation

npm install spawn-sync

If this fails, you can try one of two things:

1. You can install using --unsafe-perm, which will fix any permissions issues.

   npm install --unsafe-perm spawn-sync

2. You can upgrade to the latest version of node or iojs. This will make native compilation unnecessary.

Usage

var spawnSync = require('spawn-sync');

var result = spawnSync('node',
                       ['filename.js'],
                       {input: 'write this to stdin'});

// Note, status code will always equal 0 if using busy waiting fallback
if (result.status !== 0) {
  process.stderr.write(result.stderr);
  process.exit(result.status);
} else {
  process.stdout.write(result.stdout);
  process.stderr.write(result.stderr);
}

License

MIT