When Atom finishes loading, it will evaluate init.coffee in your ~/.atom%USERPROFILE%\.atom directory, giving you a chance to run CoffeeScript code to make customizations. Code in this file has full access to Atom's API. If customizations become extensive, consider creating a package, which we will cover in Package: Word Count.
You can open the init.coffee file in an editor from the Atom > Init ScriptFile > Init ScriptEdit > Init Script menu. This file can also be named init.js and contain JavaScript code.
For example, if you have the Audio Beep configuration setting enabled, you could add the following code to your init.coffee file to have Atom greet you with an audio beep every time it loads:
atom.beep()
Because init.coffee provides access to Atom's API, you can use it to implement useful commands without creating a new package or extending an existing one. Here's a command which uses the Selection API and Clipboard API to construct a Markdown link from the selected text and the clipboard contents as the URL:
atom.commands.add 'atom-text-editor', 'markdown:paste-as-link', ->
return unless editor = atom.workspace.getActiveTextEditor()
selection = editor.getLastSelection()
clipboardText = atom.clipboard.read()
selection.insertText("[#{selection.getText()}](#{clipboardText})")
Now, reload Atom and use the Command Palette to execute the new command, "Markdown: Paste As Link", by name. And if you'd like to trigger the command via a keyboard shortcut, you can define a keybinding for the command.