Terminal

• Terminal is the command line interface (CLI):
  • Expected output/last login
  • Prompt: provides context about cwd
  • Command line
  • Nano is a terminal text editor that provides easy-to-read instructions and is available on most systems
    • Preferable to VSCode in instances where you need to log into a remote server to edit or configure files

Terminal Shortcuts:

Command	Action
Return/Enter	submit command
Tab	Autofill file/directory name
Ctrl + A	move cursor to beginning of line
Ctrl + E	move cursor to end of line
Ctrl +U	clear line before cursor
Ctrl + K	clear line after cursor
Ctrl + L	clear terminal screen (Joe’s pro-tip)
Ctrl + C	kill what’s running
Ctrl + R	search previous commands
Ctrl + _	undo last command

Navigationg your File System

Change Directory:

Command	Action
/	top level directory
.	current directory
..	parent directory
~	home directory
cd	home directory
cd –	previous directory
pwd	print working directory
cd../..	move up two levels

File & Directory Management:

Command	Action
mkdir	create new folder
rmdir	delete empty folder
-r	delete folder and its contents
rm	delete a file
touch	create new file
cp	copy file
mv	move/rename file or folder
ls	list files and subdirectories
curl	download URL Contents to local file
curl -o	download URL Contents to local file and name file

grep

• grep (g/re/p: Globally search for a Regular Expression and Print)
  • Finds text in file(s)
  • Accepts two arguments:
    • Pattern: search value
    • Source: file to search
  • Example: Search file.txt for phrase "hello":
    grep "hello" file.txt

Options alter behavior of command line instructions and can be set with:

Shorthand Commands

Command	Action
-a	all files
-l	list format
-la	list all files
-p	parent directory
-r	recursive
-n	line number
-c	count
-s	sort entries by size
-i	warn before execution
-f	force without warning
-lt	sort entries by time modified
-lh	display files sizes (KB, MB, GB)
-lo	display size, owner, & flags

---

The Shell

• Software layer that translates CLI into actual commands
• Uses input to call applications
• Supports user environments/customization
• Operating system translates CLI to machine code to be processed by CPU

Shell Scripting

• Granting a test file permission to execute
• Create new script file with .sh extension
• Initialize shell script with #!(shebang) followed by application path:
  #!/bin/zsh

Shell Permissions

• File permissions are represented by ten characters on command line:
  

• The first character is the directory indicator

  • d: directory
  • i: file

• The directory indicator is followed by three permission groups:

  • u: user/owner
  • g: group
  • o: others

• Each group has three permissions (in order):

  • r: (read) view a file or directory’s content
  • w: (write) modify a file or directory’s content
  • x: (execute) navigate into directory and run file

• Numeric permission notation: (seen in documentation and error messages)

  • r = 4
  • w = 2
  • x = 1
    Example:
    -rw-r--r-- = 644

• Modifying permissions

• chmod (change mode) command updates a files’ permissions

  • Grant or revoke permission with + or – following group type (u, g, o)and preceding permission type ( r, w, x)
    + : grant permission
    - : revoke permission

• if permission group is not specified—all groups will be modified

  • Example: Grant (+) permission to the group (g) to read (r) a text file:
    chmod g + r file.txt

Start-Up Files

• Bash: Default shell for Linux systems; uses login and non-login shells

  • Login shell : .bash_profile is executed when bash is started manually with -l or –login
    • If no .bash_profile, bash will run .profile
  • Non(auto)-login shell: executes .bashrc automatically

• Zsh: Default shell for MacOS; only uses non(auto)-login when zsh is started

  • Executes .zshrc file

---

Git

• Git is a Version Control System (VCS) that helps us track changes to our projects over time
  • Git is the most popular VCS in use today
• The repository comprises all the source code for a particular project
• Commits are a collection of changes grouped towards a shared purpose.
• A hash is specially generated series of letters and number that identifies each commit in addition to a detailed message describing the changes
• They are 40 characters long, but Git abbreviates to seven characters
• The head is a default reference of the most recent commit
• Git maintains three lists of changes:
  • Working Directory: in-progress changes
  • Staging Area: changes ready to be committed
  • Commit History: changes already committed
• Branches are separate timelines in Git, reserved for it’s own changes/commits
  • Master branch is the default branch
• Golden rule of Git: Never modify shared branches

Git Commands

Commands	Actions
git config	Configure author name and email to be associated with commits
git init	Converts a local directory into a Git repository
git status	Lists modified files and changes that need to be added or committed
git add	Add everything within the directory to the repo
<file><file>	Add specific files to the repo
*.txt	Add all text files to the repo
git commit	Snapshot of all the files in the repository (with changes)
-m “<message>”	Label commit with message detailing changes
--amend	Alter the latest commit
	Move upwards one commit (per ^)
git diff	View changes in the working directory
--staged	View changes in Staging Area
<branch>	View changes in specific commit
<branch>^!	View changes between specific commit and commit before it
<branch><branch>	View changes between two specific commits
git log	View commit ID
git branch	View all branches in repository
-f <branch>	Directly reassign a branch to a commit
-d <branch>	Delete branch
git checkout <branch>	Switch from branch to another
-b <branch>	Create a new branch and switch to it
git merge <branch>	Merge a branch into your active branch
git clone /path/to/repository	Creates working copy of local repository
git grep “variable”	Search working directory for “variable”
git reset	Reverse changes of commit to previous commit
git revert	Reverse changes of commit and share those changes with others
git clone	Create local copies of remote repositories
git fetch	Downloads commits in remote repository that are missing from local