Day 18 #100cyberdays 🎯

💻 Today in #comptia #Linux+ class:

✅ The Bash shell is commonly used 𝒊𝒏𝒕𝒆𝒓𝒂𝒄𝒕𝒊𝒗𝒆𝒍𝒚: It lets you enter and edit commands, then executes them when you press the Enter/Return key.

⭕ However, The Bash shell can also be run 𝒏𝒐𝒏-𝒊𝒏𝒕𝒆𝒓𝒂𝒄𝒕𝒊𝒗𝒆𝒍𝒚 from a script, making the shell require no human interaction. Interactive behavior and scripted behavior should be identical. Therefore anything that can be done at the command line can be put in a script file for reuse.

✔ Scripting is a versatile tool in the field of computing and automation, serving various purposes. Today, we'll delve into the fundamentals of bash scripting, 𝒇𝒐𝒄𝒖𝒔𝒊𝒏𝒈 𝒐𝒏 𝒊𝒏𝒑𝒖𝒕, 𝒑𝒓𝒐𝒄𝒆𝒔𝒔𝒊𝒏𝒈 (𝒂𝒓𝒊𝒕𝒉𝒎𝒆𝒕𝒊𝒄), 𝒂𝒏𝒅 𝒐𝒖𝒕𝒑𝒖𝒕 𝒐𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏𝒔.

𝐖𝐫𝐢𝐭𝐞 𝐚 𝐛𝐚𝐬𝐡 𝐬𝐜𝐫𝐢𝐩𝐭 𝐭𝐡𝐚𝐭 𝐮𝐩𝐨𝐧 𝐞𝐱𝐞𝐜𝐮𝐭𝐢𝐧𝐠 𝐰𝐢𝐥𝐥:

1️⃣ Ask the user to “Enter the first number:”

2️⃣ Then, upon user entering the first number, will ask: “Enter the second number:”

3️⃣ It then assigns the command line arguments to variables num1 and num2.

4️⃣ The script performs addition, subtraction, multiplication, and division on these numbers and displays the results.

5️⃣ It also handles the case where division by zero is attempted.

🔴 Create a new file called exercise.sh using nano

$ nano exercise.sh

- The first line of the script must start with the character sequence #!, referred to as shebang1. The shebang instructs the operating system to run /bin/bash, the Bash shell, passing it the script's path as an

argument.

🔴 Then, I start writing the script as per picture. (Approaching the finale, I add a touch of fun to it!)

🔴 Make the script executable by running sudo chmod +x exercise.sh

🔴 Execute the exercise.sh script from the command line using:

$ ./exercise.sh (most commonly used, and recommended)

Thank you Dr. Harjinthar Singh

#cybersecurity #selfchallenge #100cyberdays #cybersecuritymalaysia #linux #scripting