Bash Scripting for Cybersecurity & Automation

Table of Contents

1. Introduction
2. Hello World
3. Variables
4. User Input
5. Positional Arguments
6. If-Else Statements
7. Switch Case
8. Functions
9. Piping & Redirection
10. Exit Codes
11. AWK Basics
12. SED (Stream Editor) Basics

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1. Introduction

This repository contains Bash scripting examples for automation, cybersecurity, and system administration.

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2. Hello World

#!/usr/bin/bash
echo "Hello World!"

• Run the script:

  chmod u+x hello.sh  
  ./hello.sh  

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3. Variables

Defining and Using Variables

#!/usr/bin/bash
First_Name="Pratham"
Last_Name="Chauhan"
echo "Hello $First_Name $Last_Name"

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4. User Input

#!/usr/bin/bash

echo -n "Enter your name: "
read name

echo "Hello, $name!"

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5. Positional Arguments

#!/usr/bin/bash
echo "Hello $1 $2"

• Run:

  ./script.sh Pratham Chauhan

  Output:

  Hello Pratham Chauhan
  

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6. If-Else Statements

#!/usr/bin/bash

if [ "${1,,}" = "pratham" ]; then
    echo "Welcome Back Boss"
elif [ "${1,,}" = "help" ]; then
    echo "Enter your username"
else
    echo "You are not my boss"
fi

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7. Switch Case

#!/usr/bin/bash

case "${1,,}" in 
    pratham | administrator)
        echo "Hello boss"
        ;;
    help) 
        echo "Enter your username"
        ;;
    *) 
        echo "You are not the boss"
        ;;
esac

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8. Functions

Basic Function

#!/usr/bin/bash

showname(){
    echo "Hello $1"
}

showname Pratham

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9. Piping and Redirection

ls -l /usr/bin | grep zsh

echo "Hello Pratham" > hello.txt   # Overwrites file  
echo "Hello Chauhan" >> hello.txt  # Appends to file  

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10. Exit Codes

[ 200 -eq 100 ]  
echo $?   # Returns 1 (false)  

[ 200 -eq 200 ]  
echo $?   # Returns 0 (true)  

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11. AWK Basics

awk '{print $1}' testfile.txt   # Prints first word from each line  
awk '{print $2}' testfile.txt   # Prints second word from each line  

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12. SED (Stream Editor) Basics

SED (Stream Editor) is a powerful tool for text manipulation.

Basic Find and Replace

sed 's/Pratham/He/g' sedtest.txt

Before (sedtest.txt)

Hello everyone my name is Anonymous. I am learning bash now.  
Pratham is a good boy. Pratham can do everything.  
Thank you that's from Pratham's side.  

After Running the Command

Hello everyone my name is Anonymous. I am learning bash now.  
He is a good boy. He can do everything.  
Thank you that's from He's side.  

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Delete a Specific Line

sed '3d' file.txt

Delete Lines Containing a Word

sed '/error/d' logfile.txt

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Replace Text in a File (In-Place)

sed -i 's/oldtext/newtext/g' filename.txt

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Extract Specific Lines

sed -n '2,4p' filename.txt

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Remove Empty Lines

sed '/^$/d' file.txt

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How to Use These Scripts

1. Clone the repository:

   git clone https://github.com/yourusername/bash-scripting.git
   cd bash-scripting

2. Make scripts executable:

   chmod u+x script.sh

3. Run scripts:

   ./script.sh

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Contributing

Feel free to contribute by adding more examples or improving existing ones.

🚀 Happy Scripting! 🚀