Day 39: Bash Scripting Basics: Learn Variables and Command-Line Arguments

🧠 What is Bash Scripting?

Bash scripting allows you to automate tasks in Unix/Linux environments using a sequence of shell commands inside a script file (usually ending with .sh).

Example:

#!/bin/bash
echo "Hello, DevOps!"

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🔹 Variables in Bash

✅ User-defined Variables

You can define variables without a $ and access them with a $:

name="Shaharyar"
echo "Welcome $name"

• No spaces around =

• Variables are loosely typed (strings by default)

🧪 Arithmetic with Variables:

a=10
b=5
echo $((a + b))     # Outputs: 15

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🔹 System (Environment) Variables

These are predefined variables that affect the system environment and behavior.

Example:

echo "You are in $PWD"

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🔹 Command-Line Arguments

These allow you to pass data into scripts when they are run.

Syntax:

./script.sh arg1 arg2

In the script:

• $0 = Script name

• $1 = First argument

• $2 = Second argument

• $# = Number of arguments

• $@ = All arguments

Example Script:

#!/bin/bash
echo "Script name: $0"
echo "Hello, $1! Welcome to $2."

Run:

./welcome.sh Shaharyar DevOps
# Output: Hello, Shaharyar! Welcome to DevOps.

🧭 What’s Next?

More into bash scripting