Annexure A: Command Line Cheat Sheet

Below is a quick reference for commonly used Linux commands. Use it as a handy guide for your day-to-day tasks.

File And Directory Operations

System Information

Networking

Package Management

Text Processing

Permissions And Ownership

Compression And Archiving

System Management

User Management

File Transfer

Basic Terminal Commands

date: Displays the current date and time. date For formatting, you can use flags like: 
$ date +”%Y-%m-%d %H:%M:%S”

cal: Shows a calendar of the current month. cal To see a year: $ cal 2025

man: Manual pages for commands. Very useful for detailed information. man [command] Example: $ man ls

history: Lists previously executed commands. history To rerun a command from history, use ! followed by the command number: $ !5

clear: Clears the terminal screen. $ clear

Navigation and Exploration System Commands

pwd: Prints the current working directory. $ pwd

cd: Change directory.

• To go to home directory: $ cd ~
• To go to a specific directory: $ cd /path/to/directory

To go back one directory: $ cd ..

ls: List directory contents.

• Basic usage: $ ls
• With options:
• -l for long listing format: $ ls -l
• -a to show hidden files: $ ls -a
• -h for human-readable sizes: $ ls -lh

File Administration Commands

mkdir: Make directories. $ mkdir new_directory 
To create nested directories: 
$ mkdir -p new_directory/sub_directory

cp: Copy files or directories. 
$ cp source_file destination_file 
To copy directories recursively: 
$ cp -r source_directory destination_directory

mv: Move or rename files/directories.  $ mv old_file new_file 
Or to move: $ mv file /new/location/

rm: Remove files or directories. $ rm file.txt 
To remove directories and their contents: 
$ rm -r directory_name 
Be cautious as this command is permanent; use -ifor interactive deletion: 
$ rm -i file.txt

find: Search for files in a directory hierarchy. 
$ find /path/to/search -name “pattern”
Example to find all .txt files: $ find . -name “*.txt”

locate: Quickly find files by name, using a database (needs to be updated with updatedb). locate pattern

Wildcards: Use in commands like ls, cp, mv, etc., for pattern matching.

• * for any number of characters: ls *.txt
• ? for a single character: ls file?.txt

File Content Commands

cat: Concatenate and display files. $ cat file.txt
To display multiple files: $ cat file1.txt file2.txt

head: Output the first part of files. $ head file.txt 
To see the first 10 lines: $ head -n 10 file.txt

tail: Output the last part of files. $ tail file.txt 
To follow the file for updates: $ tail -f file.txt

less: View file contents with scroll capabilities. $ less file.txt
Use arrow keys to navigate, q to quit.

touch: Create a new empty file or update the timestamp of an existing file. 
$ touch new_file.txt

nano: Simple text editor for the command line. $ nano file.txt 
Common commands: ^O to save, ^X to exit.

grep: Search text using patterns. $ grep ‘pattern’ file.txt
To search recursively: $ grep -r ‘pattern’ /directory/

Process Commands

top: Interactive process viewer. top Use q to quit.

ps: Report a snapshot of current processes. $ ps aux 
To find processes by name: $ ps aux | grep process_name

kill: Send signal to a process. 
$ kill [PID] To force terminate: $ kill -9 [PID]

Network Commands

ifconfig: Configure network interfaces 
$ ifconfig Or better use: ip addr show
(note: modern Debian uses ip command more commonly). 

ping: Check if a network host is reachable. 
$ ping google.com
To limit to 4 pings: $ ping -c 4 google.com

wget: Retrieve files from the web. 
$ wget http://example.com/file.zip 
To download in background: 
$ wget -b http://example.com/file.zip

Prev: Conclusion | Next: Annexure B