Linux CLI Drills: Files, Pipes, Processes & Ports

Introduction

The Linux command line interface (CLI) is one of the most powerful tools every developer should know. Recently, I completed a set of CLI practice drills that covered filesystem manipulation, pipes, processes, ports, and package management.

In this post, I’ll walk through the commands I used, explain what they do, and share key takeaways from each section.

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📂 Drill 1 – File System

1. Create the directory structure

mkdir -p hello/five/six/seven
mkdir -p hello/one/two/three/four

touch hello/five/six/c.txt
touch hello/five/six/seven/error.log
touch hello/one/a.txt hello/one/b.txt hello/one/two/d.txt
touch hello/one/two/three/e.txt hello/one/two/three/four/access.log

2. Delete .log files

find hello -type f -name "*.log" -delete

3. Add text to a.txt

echo "Unix is a family of multitasking, multiuser computer operating systems ..." > hello/one/a.txt

4. Delete five directory

rm -rf hello/five

5. Rename one to uno

mv hello/one hello/uno

6. Move a.txt to two directory

mv hello/uno/a.txt hello/uno/two/

Drill 2 – Pipes & Redirection

Download book

curl -o goblet.txt https://raw.githubusercontent.com/.../harry_potter_goblet_of_fire.txt

head -n 3 goblet.txt  First 3 lines

tail -n 10 goblet.txt  Last 10 lines

Find Occurrences of words:

grep -o -i "Harry" goblet.txt | wc -l
grep -o -i "Ron" goblet.txt | wc -l
grep -o -i "Hermione" goblet.txt | wc -l
grep -o -i "Dumbledore" goblet.txt | wc -l

sed -n '100,200p' goblet.txt  Lines 100–200

Unique words:

tr ' ' '\n' < goblet.txt | tr -d '[:punct:]' | tr '[:upper:]' '[:lower:]' | sort | uniq | wc -l

Processes & Ports

• List browser processes → ps -ef | grep -i firefox

• Kill browser → pkill firefox

• Top 3 CPU → ps -eo pid,ppid,cmd,%cpu --sort=-%cpu | head -n 4

• Top 3 memory → ps -eo pid,ppid,cmd,%mem --sort=-%mem | head -n 4

• Start HTTP server → python3 -m http.server 8000

• Kill server → lsof -i :8000 && kill <pid>

• Start on port 90 → sudo python3 -m http.server 90

• Show active connections → netstat -tulnp

• PID on 5432 → lsof -i :5432

Managing Software

• Install:

Install:

sudo apt install htop vim nginx   # Ubuntu
brew install htop vim nginx       # Mac

Remove:

sudo apt remove nginx   # Ubuntu
brew uninstall nginx    # Mac

Misc Commands

# 1. Local IP address
Local IP → hostname -I

# 2. IP address of google.com
nslookup google.com

# 3. Check if internet is working
ping -c 4 google.com

# 4.location of commands
which node
which code

Key Learnings

1. find, mv, and rm -rf are powerful for filesystem work.

2. Pipes (|) and redirection (>, <) let you chain commands efficiently.

3. ps, kill, and netstat are essential for managing processes and ports.

4. Package managers (apt, brew) make installing software painless.

5. Misc tools like ping, hostname, which are super handy for troubleshooting.

Conclusion

These CLI drills gave me a strong foundation in file handling, process management, networking, and software installation using Linux commands. If you’re learning the CLI, I highly recommend practicing these exercises step by step — they’ll save you hours in real-world debugging.