Execute a command line binary with Node.js

When to choose which approach

Asynchronous execution using Promises

Harness the power of Node.js's util.promisify to turn callback-based functions into promise-friendly functions. Essential for powerful error handling and executing multiple asynchronous binaries.

const util = require('util');
const exec = util.promisify(require('child_process').exec);

async function runBinary() {
  try {
    const { stdout, stderr } = await exec('your-binary');
    console.log(stdout);
    console.error(stderr);
  } catch (error) {
    console.error(`Execution error: ${error}`); // Catching errors, so they don't catch us off-guard!
  }
}
runBinary();
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Running files directly with execFile

Use execFile when running binary files. It's safer since it doesn't spawn a shell, thus adding a layer of security precaution against shell parameter injection.

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

execFile('/path/to/your-binary', ['arg1', 'arg2'], (error, stdout, stderr) => {
  if (error) throw error; // If things go south, we'll know.
  console.log(stdout);
});


Replace '/path/to/your-binary' with the direct path and add any arguments in the array.

Handling output & errors wisely

Getting streamed data using spawn

Use child_process.spawn to deal with long outputs or interactive processes. It provides a stream of data that you can handle as it arrives.

const { spawn } = require('child_process');
const child = spawn('your-long-running-binary');

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

child.stderr.on('data', (chunk) => {
  console.error(`stderr chunk: ${chunk}`); // Oh no, an error chunk! Not as tasty as a chocolate chunk!
});

child.on('exit', (code) => {
  console.log(`Child process exited with code ${code}`);
});


Synchronous execution and its impact

execSync and spawnSync provide immediate output, but be aware of their implications on the Node.js event loop.

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

let output = execSync('your-binary');
console.log(output.toString()); // It's sync, like *NSYNC, but instead of harmonious pop music, you get immediate output (and a potentially blocked Node.js event loop)!


Use synchronous execution sparingly. Excessive use may reduce your application's responsiveness.

Mind the platform

Environment compatibility

Command line binaries might differ across Unix and Windows. Do thorough testing to avoid unpleasantries.

Ensuring the syntax is correct

Command strings should be correctly formatted for the system's shell environment. "A stitch in time saves nine."

Staying in the loop

Language feature updates

Node.js keeps evolving. Hence, don't blink, or you will miss updates on child_process module and other core APIs.

Valid and verified references

The official Node.js documentation is your ultimate guide for understanding all available methods within the 'child_process' module.

Looking at specifics

Complex scenarios

child_process methods provide an arrays of configuration options to handle complex execution scenarios.

Error handling and exit codes

Catching and addressing error outputs and process exit codes are critical.