child_processes.md

5. Child Processes (Basics, no IPC/fork) 7%

Spawn vs Fork vs Exec

• require('child_process').spawn(); - large data, stream, NOT a new V8 instance
• require('child_process').fork(); - new V8 instance, multiple workers
• require('child_process').exec(); - buffer, async, all the data at once

Spawn

Example

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

spawn('node', 'program.js').stdout.on('data', data => {
    console.log('stdout: ' + data);
});

Fork

Example

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

fork('program.js').stdout.on('data', data => {
    console.log('stdout: ' + data);
});

Exec

Example

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

exec('node program.js', (error, stdout, stderr) => {
    if (error) console.log(error.code);
});

There are few more methods

• execFile() - is similar to exec() except that it does not spawn a shell by default. Rather, the specified executable file is spawned directly as a new process making it slightly more efficient than exec()

And sync versions of exec and execFile

• execSync()
• execFileSync()