Notes

Navigating your File System

• Command Line : The line in which we enter our commands.
• Prompt : The bit of text before your CL that gives some context to your pwd.
• Output : Anything that’s been executed to the terminal.

Keyboard Shortcuts

• Return & Enter : Submit code we have typed.
• Up & Down Arrows : Move up and Down your command history.
• ctrl + a : Move your cursor to the beginning of the line.
• ctrl + e : Move your curse to the end of the line.
• ctrl + l : clear your terminal.

Understanding Directories

• /User/your_username/ or ~ : Home Directory.
• / : The Root Directory.
• . : Current Directory
• .. : Parent of Current Directory.

Getting Around

• pwd : Print Working Directory, will always print the full path of where you are.
• You can append -al to ls in order to see all the hidden files as well.

Making Changes

• touch : command used to create files.
• mkdir : command to make directories.

• appending -p to mkdir will allow you to make all required parent directories it needs to create a requested directory.

  > mkdir -p ~/none/of/these/directories/exist/but/now/they/will

  Manipulating Existing Files

• cp : duplicates a file, requires a source and a destination.
• mv : moves a file from one place to another, can also be used to rename files.
• rm: removes files and directories.
  • Be very careful with this command, you will not be able to recover deleted items!

• rmdir : for removing directories only.

Command Tasks on the Command Line

Grep marks the spot

g/re/p means “Globally search for a Regular Expression and Print”

• grep accepts two arguments: a pattern and a source to search.

Common grep options

• -r : recursive - searches all files in a given path.
• -n : line number - will show you the exact line for each match.
• -i : ignore case.
• -c : will return count, the number of matches.

Teaching yourself anything

• man : (manual) utility to learn more about any built in command.
  • Use arrow keys to navigate.
  • Use Q on to quit the manual.

Command Redirection

• Command Redirection : Takes the output from one command makes it the input for another command.

  > man grep | grep -C1 count

• > : will create a new file to save output.
• >> : will append output to an existing file.
• The redirection operators are very fast but do not show you the output before writing it to a given file.
  • tee : the tee operator can be used to view an output before writing it to a file.

Editing files directly from the CLI

Nano is a terminal text editor that provides easy-to-read instructions and is available on most systems.

• Terminal editors are preferable to VSCode in instances where you need to log into a remote server to edit or configure files.

Bringing the Internet into your Terminal

• curl : command used to download from a URL to your computer.
• -o : appending this flag to your curl command will allow you to name the incoming download file.

Understanding the Shell

• shell : the software layer that translates your command line instructions into actual commands.
  • Calls applications using your input.
  • Supporting User Environments & Customization.

Selling C-Shells by the Seashore

• Bash : Default shell for Linux systems.
• Zsh : Default shell for MacOS.
  • Has scripting compatibility with Bash Shells but not the other way around.

Shells vs Terminals

Shells and Terminals are not the same thing, just think of a terminal as an emulator that allows us to work with our Shell.

Shell Prompts

If we ever see a # instead of the usual $ or %, we are logged in as a super-user and must take great care!

Two Purposes

• The first purpose of your shell is to execute commands.
• The second purpose is customization of your unique environment - such as using environment variables.

From the Command Line to the Screen

Customizing your Environment

• Export : command used to change/initialize a new environment variable

  $ export NEW_VARIABLE=value

• Bash Customizable Files: .profile, .bash_profile, .bashrc.

• Zsh Customizable Files: .zshrc.

Bash Startup Files

• Use -l or –login to run your bashrc file.

ZSH Startup Files

• Zsh file is started anytime you use both login and non-login shells.

macOS Catalina with Zsh

Put your customizations into your .zshrc file. Change Visual Studio Code to use zsh as it’s shell.

Bash Permissions & Scripting

• The CLI comprises the first ten characters.
• It goes in order like this: directory indicator, owner, group, others.
  • r : 4 points.
  • w : 2 points.
  • x : 1 point.

Modifying Permissions

• chmod : command to update the permissions of a file ourselves. (change mode)

Ignoring Permissions entirely with Sudo

Bash Scripting

• Script requirements

  • An effective script requires three things:

    • An interpreter directive
    • A commented description
    • A script body