Terminal Basics¶

The terminal (terminal emulator) provides a window to interact with the shell - the command-line interpreter that passes user input to the OS kernel. This entry covers shell types, essential commands, and keyboard shortcuts for efficient terminal usage.

Key Facts¶

The shell interprets commands; the terminal is the GUI window hosting the shell
Default shell on most Linux distros: bash (Bourne Again Shell)
Shells available: sh, bash, dash, zsh, fish
Linux filesystem is case-sensitive: File.txt and file.txt are different files
SSH default port: 22

Shell Types¶

Shell	Notes
sh (Bourne)	POSIX standard, basic
bash	Most popular, default on most distros, extends sh
dash	Lightweight POSIX shell, default `/bin/sh` on Ubuntu, fast startup
zsh	Shared history, improved arrays, spell correction, plugins (Oh My Zsh)
fish	Syntax highlighting, fast history search, web configurator

echo $SHELL         # current shell path
echo $0             # current shell name
cat /etc/shells     # all available shells
chsh -s /bin/zsh    # change default login shell

Shell config files: - bash: ~/.bashrc (interactive), ~/.bash_profile (login), ~/.bash_logout - zsh: ~/.zshrc - Global: /etc/profile, /etc/bash.bashrc

Essential First Commands¶

pwd             # print working directory
whoami          # print current username
clear           # clear screen (also Ctrl+L)
reset           # reset terminal to default state
history         # show command history
history -c      # clear history

# Getting help
man command     # full manual page
command --help  # brief usage info
whatis command  # one-line description
apropos keyword # search help by keyword
info command    # info page (alternative to man)

cd /path/to/dir   # absolute path
cd ~              # home directory (also just cd)
cd ..             # one level up
cd -              # previous directory
ls                # list contents
ls -l             # long format (permissions, size, date)
ls -a             # show hidden files (starting with .)
ls -la            # long + hidden
tree              # display directory tree

Shortcut	Action
Ctrl+A	Move to start of line
Ctrl+E	Move to end of line
Alt+F	Move one word forward
Alt+B	Move one word backward
Ctrl+XX	Toggle between start and current position

Keyboard Shortcuts - Editing¶

Shortcut	Action
Ctrl+U	Delete from cursor to start of line
Ctrl+K	Delete from cursor to end of line
Ctrl+W	Delete word before cursor
Alt+D	Delete from cursor to end of word
Ctrl+D	Delete character under cursor
Alt+.	Insert last argument of previous command

Keyboard Shortcuts - Process Control¶

Shortcut	Action
Ctrl+C	Kill current command (SIGINT)
Ctrl+Z	Suspend current command (background)
Ctrl+D	Close terminal / send EOF
Ctrl+L	Clear screen
Ctrl+S	Stop output to screen
Ctrl+Q	Resume output

Keyboard Shortcuts - History¶

Shortcut	Action
Ctrl+R	Reverse incremental history search
Up / Ctrl+P	Previous command
Down / Ctrl+N	Next command
!!	Run last command
!x	Run last command starting with x
^old^new	Replace old with new in last command

Getting Linux¶

WSL (Windows 10+): best option for Windows users, install from Microsoft Store
VirtualBox: any distro as VM (2GB+ RAM, 20GB+ disk)
Cloud VPS: connect via SSH
macOS: native Unix terminal, use brew as package manager

Gotchas¶

cd with no arguments goes to ~ (home), not /
Ctrl+S freezes terminal output - use Ctrl+Q to unfreeze (common panic moment)
history -c clears in-memory history but not ~/.bash_history file - use history -c && history -w to clear both
Tab completion is context-aware: first Tab completes, double-Tab shows all options