Could we run an external process with Node.js?

Yes, you can run an external process with Node.js using the child_process module, which provides the ability to spawn subprocesses. This module includes several methods to create and manage child processes, such as exec, spawn, execFile, and fork.

1. Using exec: This method is used to execute a command in a shell and buffer the output. It is suitable for running commands that do not produce a large amount of output to avoid memory issues since it buffers the output.

   javascript Copy

   const { exec } = require('child_process');
   exec('ls', (error, stdout, stderr) => {
     if (error) {
       console.error(`exec error: ${error}`);
       return;
     }
     console.log(`stdout: ${stdout}`);
     console.error(`stderr: ${stderr}`);
   });

2. Using spawn: This method launches a new process with a given command. It's more suitable for commands that generate large amounts of data because it streams the data through stdout and stderr, without buffering it.

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   const { spawn } = require('child_process');
   const child = spawn('ls', ['-lh', '/usr']);
   
   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}`);
   });

3. Using execFile: This method is similar to exec but does not spawn a shell by default. It's more efficient when you need to execute a file rather than a command.

   javascript Copy

   const { execFile } = require('child_process');
   execFile('node', ['--version'], (error, stdout, stderr) => {
     if (error) {
       throw error;
     }
     console.log(stdout);
   });

4. Using fork: This method is a special case of spawn that spawns a new Node.js process and establishes a communication channel between the parent and child process. It's useful for executing heavy JavaScript tasks in parallel without blocking the event loop.

   javascript Copy

   const { fork } = require('child_process');
   const forked = fork('script.js');
   
   forked.on('message', (msg) => {
     console.log('Message from child', msg);
   });
   
   forked.send({ hello: 'world' });

Each of these methods is suited to different scenarios depending on the requirements of the external program you need to run, such as the expected volume of output data and whether or not you need a shell to execute the command[1][3][5][6][7][13][14].

Citations:
[1] https://stackoverflow.com/questions/5775088/how-to-execute-an-external-program-from-within-node-js
[2] https://nodejs.org/api/process.html
[3] https://nodejs.org/api/child_process.html
[4] https://stackoverflow.com/questions/40065682/using-the-exec-method-in-node-js
[5] https://2coffee.dev/en/articles/what-is-child-process-in-nodejs-when-to-use-fork-and-spawn
[6] https://www.geeksforgeeks.org/how-can-we-run-an-external-process-with-node-js/
[7] https://blog.logrocket.com/node-js-child-process-launch-external-programs/
[8] https://www.geeksforgeeks.org/node-js-child-process/
[9] https://topdev.vn/blog/child-process-trong-node-js-la-gi/
[10] https://www.javatpoint.com/nodejs-child-process
[11] https://www.oreilly.com/library/view/professional-nodejs-building/9781118240564/xhtml/Chapter08.html
[12] https://www.freecodecamp.org/news/node-js-child-processes-everything-you-need-to-know-e69498fe970a/
[13] https://www.digitalocean.com/community/tutorials/how-to-launch-child-processes-in-node-js
[14] https://www.edureka.co/community/77566/how-to-execute-an-external-program-from-within-node-js
[15] https://www.tutorialspoint.com/nodejs/nodejs_scaling_application.htm
[16] https://nodejs.org/en/learn/command-line/run-nodejs-scripts-from-the-command-line
[17] https://www.w3schools.com/jsref/jsref_regexp_exec.asp
[18] https://developer.mozilla.org/vi/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec
[19] https://www.youtube.com/watch?v=8qSYHUa1eJEWhen considering the use of global variables in Node.js, it's important to weigh both their advantages and disadvantages to determine when their use might be appropriate or necessary.

Advantages of Using Global Variables

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