Introduction to the Command Line Interface

Nearly ever computer comes with a CLI

• Windows: Git Bash (See "Introduction to Git")
• Mac/Linux: Terminal

The CLI can help you:

• Navigate folders
• Create files, folders, and programs
• Edit files, folders, and programs
• Run computer programs

• "Directory" is just another name for folder
• Directories on your computer are organized like a tree
• Directories can be inside other directories
• We can navigate directories using the CLI

• My "Debussy" directory is contained inside of my "Music" directory

• One directory "up" from my Debussy directory is my Music directory

• The directory structure on your computer looks something like this

• The directory at the top of the tree is called the root directory
• The root directory contains all other directories
• The name of this directory is represented by a slash: /

• Your home directory is represented by a tilde: ~
• Your home directory usually contains most of your personal files, pictures, music, etc.
• The name of your home directory is usually the name you use to log into your computer

Windows users:

• Open the start menu
• Search for Git Bash
• Open Git Bash

Mac users:

• Open Spotlight
• Search Terminal
• Open Terminal

• When you open your CLI you will see your prompt, which will looks something like the name of your computer, followed by your username, followed by a $
• When you open your CLI you start in your home directory.
• Whatever directory directory you're currently working with in your CLI is called the "working directory"

• You can imagine tracing all of the directories from your root directory to the directory you're currently in.
• This is called the "path" to your working directory.

• In your CLI prompt, type pwd and press enter.
• This will display the path to you're working directory.
• As you can see we get the prompt back after entering a command.

• You use the CLI prompt by typing in a command and pressing enter.
• pwd can be used at any time to display the path to your working directory (pwd is an abbreviation for "print working directory")

• CLI commands follow this recipe: command flags arguments
• command is the CLI command which does a specific task
• flags are options we give to the command to trigger certain behaviors, preceded by a -
• arguments can be what the command is going to modify, or other options for the command
• Depending on the command, there can be zero or more flags and arguments
• For example pwd is a command that requires no flags or arguments

• pwd displays the path to the current working directory

jeff$ pwd
/Users/jeff
jeff$ 

• clear will clear out the commands in your current CLI window

jeff$ pwd
/Users/jeff
jeff$ clear

jeff$

• ls lists files and folders in the current directory
• ls -a lists hidden and unhidden files and folders
• ls -al lists details for hidden and unhidden files and folders
• Notice that -a and -l are flags (they're preceded by a -)
• They can be combined into the flag: -al

jeff$ ls
Desktop   Photos   Music    
jeff$ ls -a
Desktop   Photos   Music  .Trash  .DS_Store
jeff$

• cd stands for "change directory"
• cd takes as an argument the directory you want to visit
• cd with no argument takes you to your home directory
• cd .. allows you to chnage directory to one level above your current directory

jeff$ cd Music/Debussy
jeff$ pwd
/Users/jeff/Music/Debussy
jeff$ cd ..
jeff$ pwd
/Users/jeff/Music
jeff$ cd
jeff$ pwd
/Users/jeff
jeff$

• mkdir stands for "make directory"
• Just like: right click -> create new folder
• mkdir takes as an argument the name of the directory you're creating

jeff$ mkdir Documents
jeff$ ls
Desktop   Photos  Music   Documents
jeff$ cd Documents
jeff$ pwd
/Users/jeff/Documents
jeff$ cd
jeff$

• touch creates an empty file

jeff$ touch test_file
jeff$ ls
Desktop   Photos  Music   Documents   test_file
jeff$

• cp stands for "copy"
• cp takes as its first argument a file, and as its second argument the path to where you want the file to be copied

jeff$ cp test_file Documents
jeff$ cd Documents
jeff$ ls 
test_file
jeff$ cd ..
jeff$

• cp can also be used for copying the contents of directories, but you must use the -r flag
• The line: cp -r Documents More_docs copies the contents of Documents into More_docs

jeff$ mkdir More_docs
jeff$ cp -r Documents More_docs
jeff$ cd More_docs
jeff$ ls 
test_file
jeff$ cd ..
jeff$

• rm stands for "remove"
• rm takes the name of a file you wish to remove as its argument

jeff$ ls
Desktop   Photos  Music   Documents   More_docs   test_file
jeff$ rm test_file
jeff$ ls
Desktop   Photos  Music   Documents   More_docs
jeff$

• You can also use rm to delete entire directories and their contents by using the -r flag
• Be very careful when you do this, there is no was to undo an rm

jeff$ ls
Desktop   Photos  Music   Documents   More_docs
jeff$ rm -r More_docs
jeff$ ls
Desktop   Photos  Music   Documents
jeff$

• mv stands for "move"
• With mv you can move files between directories

jeff$ touch new_file
jeff$ mv new_file Documents
jeff$ ls
Desktop   Photos  Music   Documents
jeff$ cd Documents
jeff$ ls
test_file   new_file
jeff$

• You can also use mv to rename files

jeff$ ls
test_file   new_file
jeff$ mv new_file renamed_file
jeff$ ls
test_file renamed_file
jeff$

• echo will print whatever arguments you provide

jeff$ echo Hello World!
Hello World!
jeff$

• date will print today's date

jeff$ date
Mon Nov  4 20:48:03 EST 2013
jeff$

• pwd
• clear
• ls
• cd
• mkdir
• touch
• cp
• rm
• mv
• date
• echo