Why bin/www file doesn't have extension in express-generator?

Question

I always have this doubt and I don't know why the file inside the bin folder which create a simple http server doesn't have a .js extension.

Is there a reason behind this?

Answer 1

It's tradition on unix that executables don't have extension.

For example, on Linux and MacOS to list a directory you type:

ls

you don't type

ls.exe

Another example, to launch the Dropbox service on Linux you can type

dropbox

you don't type

dropbox.py

even though dropbox is just a text file containing Python code.

Unix (and also bash terminal on Windows) have a feature where if a file is marked as executable (using the chmod command) and the first line contains:

#!

.. then the shell (the program controlling the command line) will remove the first two characters (#!) and execute the rest of that first line. This is often called the shbang line (sh = shell, ! = bang).

Therefore, if you want to develop a command-line program in node.js all you need to do is start the file with #! /usr/bin/env node:

#! /usr/bin/env node
//       ^
//       |
//  the 'env' command will find the correct install path of node

console.log('hello world');

Then use chmod to make the file executable:

chmod +x my-script.js

Of course, creating a program that ends in .js does not look "professional". For example you don't type gulp.js when you run gulp and you don't type npm.js when you run npm. So people follow tradition and make their executable scripts have no extension - it makes it harder for people to realise that you didn't write the program in C or assembly language.