What Is a Script?

A script is:

A text file that contains a list of commands.

When you run the script, the system executes each command in order.

Think of it like:

Instead of telling someone step-by-step what to do every time, you write instructions once and hand them over whenever needed.

Why Use Scripting?

Scripting helps you:

• Automate repetitive tasks
• Save time
• Reduce human error
• Perform complex operations easily
• Run tasks on multiple files at once

Example tasks:

• Backing up files
• Renaming many files
• Starting multiple programs
• Cleaning temporary files

Basic Bash Script (Linux/macOS)

On Linux or macOS, scripting is often done using Bash.

Create a file called:

myscript.sh

Example:

#!/bin/bash

echo "Hello, world!"
echo "This is my first script."

mkdir TestFolder
cd TestFolder
touch example.txt

echo "Script finished."

Explanation:

• #!/bin/bash tells the system to use Bash.
• echo prints text.
• mkdir creates a folder.
• cd changes directory.
• touch creates a file.

To make it executable:

chmod +x myscript.sh

To run it:

./myscript.sh

Basic Batch Script (Windows)

On Windows, basic scripting is often done using batch files.

Create a file called:

myscript.bat

Example:

@echo off

echo Hello, world!
echo This is my first script.

mkdir TestFolder
cd TestFolder
type nul > example.txt

echo Script finished.
pause

Explanation:

• @echo off hides command repetition.
• echo prints text.
• mkdir creates a folder.
• cd changes directory.
• type nul > file.txt creates a file.
• pause waits for user input.

To run it:

Double-click the file

or run from Command Prompt:

myscript.bat

Variables in Scripts

Scripts can store information using variables.

Bash Example

#!/bin/bash

name="John"
echo "Hello, $name"

Windows Batch Example

@echo off

set name=John
echo Hello, %name%
pause

Variables allow your script to become dynamic.

Simple User Input

Bash

#!/bin/bash

echo "Enter your name:"
read name
echo "Hello, $name"

Windows Batch

@echo off

set /p name=Enter your name:
echo Hello, %name%
pause

Now the script interacts with the user.

Basic Conditional Logic

Scripts can make decisions.

Bash

#!/bin/bash

number=10

if [ $number -gt 5 ]; then
    echo "Number is greater than 5"
fi

Windows Batch

@echo off

set number=10

if %number% GTR 5 (
    echo Number is greater than 5
)

pause

This allows scripts to behave differently depending on conditions.

Basic Loop Example

Loops repeat commands.

Bash

#!/bin/bash

for i in 1 2 3
do
    echo "Number $i"
done

Windows Batch

@echo off

for %%i in (1 2 3) do (
    echo Number %%i
)

pause

How Scripts Work Internally

When you run a script:

1. The shell reads the file.
2. It interprets each line.
3. It executes commands one by one.
4. It stops if an error occurs (depending on settings).

A script is not compiled like a traditional program.

It is interpreted line by line.