Terminal

To access the command line interface on macOS you need to open Terminal. It is located in /Applications/Utilities/Terminal; the easiest way to open it is to use spotlight (⌘+space) and simply type terminal.

An alternative to Terminal is iTerm. iTerm is a terminal emulator that can be used as a replacement for the native Terminal app. iTerm adds a host of new features that provided much needed productivity boosters like autocompletion and split panes.

Basic Commands

Below are a few basic commands that form the bedrock of command line interaction. If you ever have any questions about a command you come across, Explain Shell is an excellent resource as well as this cheatsheet.

Before we begin, here are a few tips:

• The term “directory” is just a way of referring to folders; “directory” is preferred on *nix operating systems as opposed to “folder” on Windows (checkout this for the super nerd answer)

• The action that a command performs can be modified using flags. These are typically a “-” followed by a single letter. For example, to list the visible AND the hidden the contents in a directory you would type the list command ls followed by the flag -a.

Creating Files and Folders

• mkdir [dir_name] make a directory

• touch [file_name] change file timestamps; easy way to create files

• rm [file_name] removes files (does not remove directories by default)
  • -r [dir_name] remove directories and their contents recursively

Moving Around and Exploring the Computer

• cd traverse the directory structure forward (i.e., open a directory)

• ../ traverse the directory structure backward (i.e., exit a directory)

• ls list contents of current directory
  • -l list detailed info such as permissions, owners, size, etc.
  • -a list all contents including hidden contents
  • -S sort
  • Sr reverse sort

• cp [file] [path] copy source file to a destination

• mv rename source to destination or move source to a directory; whereas cp duplicates the file, mv only keeps one copy (either with the new name or in the new location)

• grep ["pattern"] [file_name] print lines matching a pattern

• find [file_name] find a file

• cat [file_name] display contents of file

• echo ["string"] display a line of text

Other Useful Commands

• sudo [command] execute command as super user (requires password)

• [command] | [command] piping — feed output of one command into the input of another command

• echo ["string"] > [file_name] overwrite file with string
  • echo ["string"] >> [file_name] append file with string
• Text editors
  • nano [file_name] a very simple text editor
  • vim [file_name] a more robust and extensible text editor; type esc then :q to exit
  • emacs [file_name] a more robust and extensible text editor

Shells

While terminal is an application, the underlying software that you are using to do the command line interfacing is known as a shell. The default shell for macOS is Bash (Bourne Again Shell). Although Bash has stood the test of time, I currently using Zsh (pronounced Zee Shell) which provides useful features like command line completions, spell corrections, themeable prompts, etc.

brew install zsh zsh-completions