Day 3: Mastering Basic Linux Commands 🚀

In today's task, we will cover essential Linux commands that are frequently used in day-to-day DevOps activities. This practical guide includes viewing files, managing permissions, handling file contents, and more. Let's dive in!

Task 1: View the Content of a File with Line Numbers 📄

Linux provides the cat command to display the contents of a file. To display line numbers along with the content, we use the -n option.

Command :

cat -n chintamani.txt

Example :

This command prints the content of chintamani.txt with line numbers.

Task 2: Change File Permissions (Read, Write, Execute) 🔒

The chmod command is used to change file permissions. Here, we make the file readable, writable, and executable by the owner only.

Command :

chmod 700 chintamani.txt

Example :

This command sets permissions for the owner to read, write, and execute the file.

Task 3: Check the Last 10 Commands Executed 📝

We often need to check our command history. The history command helps, and we can use tail to show only the last 10 commands.

Command :

history | tail -10

Example :

his command shows the last 10 commands that you executed in your terminal.

Task 4: Remove a Directory and All Its Contents 🗑️

The rm command is used to remove files and directories. To remove a directory along with all its contents, use the -r option.

Command :

rm -r chintamani.txt

Example :

This will remove the directory and all its files permanently.

Task 5: Create and Display a File 📝

Creating a file and adding content is easy with the echo command. We can use it to write multiple lines into a file.

Command:

vim fruits.txt
cat fruits.txt

Example :

This will create a fruits.txt file with fruit names on each line and then display the contents using cat.

Task 6: Append to a File 📥

Appending data to an existing file is also simple using the echo command.

Command :

echo "Pineapple" >> fruits.txt
cat fruits.txt

Example :

This will append the word "Pineapple" to the end of the fruits.txt file.

Task 7: Display the First 3 Fruits in Reverse Order 🔄

We can use head to show the first few lines of a file, and tac to reverse them.

Command :

head -3 fruits.txt | tac

Example :

This command will display the first three fruits from the file in reverse order.

Task 8: Show the Last 3 Fruits and Sort Alphabetically 🔤

Similarly, we can use tail to get the last few lines and sort to organize them alphabetically.

Command:

tail -3 fruits.txt | sort

Example :

This shows the last 3 fruits, sorted in alphabetical order.

Task 9: Create a colors File and Display Content

Let’s create a Colors.txt file and add colors line by line.

Command:

echo -e "Red\nPink\nWhite\nBlack\nOrange\nPurple\nGrey" > colors.txt
cat colors.txt

Example :

his command creates a colors.txt file and lists colors one by one.

Task 10: Prepend Content to a File 🛠️

Prepending content to a file is not as straightforward as appending. But we can manage using a trick.

Command:

echo "Yellow" | cat - colors.txt > temp && mv temp colors.txt
cat colors.txt

Example :

This will add "Yellow" at the beginning of colors.txt.

Task 11: Find Common Lines Between Two Files 📑

To compare two files and find common lines, we use the comm command.

Command:

comm -12 <(sort fruits.txt) <(sort colors.txt)

Example :

This command will show the lines common between fruits.txt and colors.txt.

Task 12: Count Lines, Words, and Characters 🧮

The wc command gives the number of lines, words, and characters in a file.

Command:

wc fruits.txt colors.txt

Example :

This will count and display the lines, words, and characters for both files.

Wrapping Up 🎉

These are some of the most basic but useful Linux commands for managing files and permissions. Performing these tasks not only helps you understand the command-line better but also builds a strong foundation for working with Linux in DevOps environments.

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