Day 3 - Mastering Linux Commands

#90daysdevopschallenge #womenintech #devops #linux

In DevOps, Linux isn't just an operating system — it's the backbone of cloud infrastructure, automation, and deployment.

The task for day 3 simply explains the intricacies of creating files, setting permissions, manipulating content etc.,
but here's why it really matters:

Security
Understanding file permissions (chmod, chown) ensures that only the right users have access. This is critical for protecting sensitive data and preventing system breaches.
Automation & Scripting
Commands like cat, echo, head, tail, and sort are the building blocks of automation. Mastering them means you can write shell scripts to manage systems, process logs, and deploy code at scale.
Data Manipulation
Working with files — reading, writing, appending, sorting — is a core part of system administration. These commands make you efficient and effective at handling real-world data.
Foundation for Advanced Tools
Whether it’s Docker, Kubernetes, Ansible, or Jenkins — they all rely on Linux environments. Understanding how to operate confidently in the terminal is essential for working with these tools.

Task	Linux Command
1. View the content of a file and display line numbers	`cat -n filename.txt` or `nl filename.txt`
2. Make file readable, writable, executable by owner only	`chmod 700 filename.txt`
3. Check the last 10 commands you have run	`history	tail -10`
4. Remove a directory and all its contents	`rm -r directory_name`
5. Create `fruits.txt`, add content (one fruit per line), and display it	cat > fruits.txt Apple Mango Banana Cherry Kiwi Orange Guava <Ctrl + D> cat fruits.txt
6. Create `devops.txt` and append “Pineapple”	cat > devops.txt Apple Mango Banana Cherry Kiwi Orange Guava <Ctrl + D> echo "Pineapple" >> devops.txt
7. Show the first three fruits in reverse order	`head -n 3 devops.txt	tac`
8. Show the bottom three fruits and sort alphabetically	`tail -n 3 devops.txt \	sort`
9. Create `Colors.txt`, add one color per line, and display it	cat > Colors.txt Red Pink White Black Blue Orange Purple Grey <Ctrl + D> cat Colors.txt
10. Prepend "Yellow" to the beginning of `Colors.txt`	`sed -i '1iYellow' Colors.txt`
11. Find and display common lines between both files	`comm -12 <(sort fruits.txt) <(sort Colors.txt)`
12. Count lines, words, and characters in both files	`wc fruits.txt Colors.txt`