How to use the Node.js child_process module for running external commands



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The child_process module in Node.js allows you to spawn child processes and interact with them. You can use it to run external commands and handle their input, output, and errors. Here's a basic guide on how to use the child_process module:

Using spawn:

The spawn function is used to start a new process and it returns a ChildProcess object. It's suitable for long-running processes with a stream of data.

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

const command = 'ls';
const args = ['-l', '-a'];

const child = spawn(command, args);

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

child.stderr.on('data', (data) => {
  console.error(`stderr: ${data}`);
});

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

Using exec:

The exec function is used when you want to run a command in a shell and buffer the output. It's suitable for short-lived commands.

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

const command = 'ls -l -a';

exec(command, (error, stdout, stderr) => {
  if (error) {
    console.error(`exec error: ${error}`);
    return;
  }
  console.log(`stdout: ${stdout}`);
  console.error(`stderr: ${stderr}`);
});

Using execFile:

The execFile function is similar to exec but it allows you to specify the exact executable file to run.

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

const command = 'ls';
const args = ['-l', '-a'];

execFile(command, args, (error, stdout, stderr) => {
  if (error) {
    console.error(`execFile error: ${error}`);
    return;
  }
  console.log(`stdout: ${stdout}`);
  console.error(`stderr: ${stderr}`);
});

Using fork:

The fork function is used to spawn a new Node.js process and execute a specified module with an IPC (Inter-Process Communication) channel.

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

const child = fork('child.js');

child.on('message', (message) => {
  console.log(`Message from child: ${message}`);
});

child.send({ hello: 'world' });

These are some basic examples to get you started. Make sure to handle errors appropriately, and be cautious when dealing with user input to prevent security vulnerabilities like command injection.

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