Shell_Scripting

**\>> Shell – It is utility which allow us to talk to kernel .

\>> Bash – It is kind of shell. It is more popular shell. Born again shell. It is end with .sh .

\>> sh – It is also shell.

\>> write the first bash scripting .

shebang - #!/bin/bash - This will always come whenever we start script .

\>>vi hello.sh and write below script**

#!/bin/bash

echo "Gabbar: Kitne aadmi the"

echo "Sambha: 2 sarkar"

\>> then chmod 777 hello.sh**

Below is the output of script:

\>> ./hello.sh

root@ip-172-31-45-40:~/Scripts# ./hello.sh

Gabbar: Kitne aadmi the

**Sambha: 2 sarkar

\==================================================================================

\>>Second script**

#!/bin/bash

echo "Gabbar: Kitne aadmi the"

echo "Sambha: 2 sarkar"

echo "Gabbar: Kitna bja hai"

date

echo "Gabbar : kitne baje se class chal rha hai"

**uptime

\>> output :

root@ip-172-31-45-40:~/Scripts# ./hello.sh**

Gabbar: Kitne aadmi the

Sambha: 2 sarkar

Gabbar: Kitna bja hai

Tue Oct 15 10:20:43 UTC 2024

Gabbar : kitne baje se class chal rha hai

**10:20:43 up 4 min, 2 users, load average: 0.02, 0.13, 0.07

\=========================================================
// Another script where we can write Comment .//

#!/bin/bash**

#this is sholay story by Rajan

<<Comment

This is multiline comment

Comment

echo "Gabbar: Kitne aadmi the"

echo ""

echo "Sambha: 2 Sarkar"

echo ""

echo "Gabbar: Kitna bja hai"

echo ""

date

echo ""

echo "Gabbar: kitne der se class chal rha hai"

echo ""

**uptime

output of script :

root@shellMachine:/home/ubuntu/script# ./hello.sh**

Gabbar: Kitne aadmi the

Sambha: 2 Sarkar

Gabbar: Kitna bja hai

Mon Dec 2 02:34:07 UTC 2024

Gabbar: kitne der se class chal rha hai

**02:34:07 up 38 min, 1 user, load average: 0.00, 0.00, 0.00

\===========================================================
//Variables and Constant //

\>> Variable – Anything that is vary called variable .

a = 2 - Here a is variable and 2 is constant .

write the below script :

\>> variable.sh

#!/bin/bash**

<<Note

This is demo for variables.

Note

Name="Rajan"

echo "My name is $Name"

**Output :

root@shellMachine:/home/ubuntu/script# ./variables.sh**

**My name is Rajan

\===========================================================**

**//Another script for variables//

#!/bin/bash**

<<Note

This is demo for variables.

Note

Name="Rajan"

echo "My name is $Name"

echo "What is your name"

Name2="Anoop"

**echo "My name is $Name2

output :

root@shellMachine:/home/ubuntu/script# ./variables.sh**

My name is Rajan

What is your name

My name is Anoop

**\>> We can ask input from users as well :

#!/bin/bash**

<<Note

This is demo for variables.

Note

echo "Enter the name"

read Name

echo "My name is $Name"

echo "What is your name"

read Name2

**echo "My name is $Name2"

Output :

\>> vi greeting.sh

#!/bin/bash**

# Define variables

USER_NAME="User"

GREETING="Hello"

COUNTER=1

# Greeting the user

echo "$GREETING, $USER_NAME!"

# Loop to count from 1 to 5

echo "Counting from 1 to 5:"

while [ $COUNTER -le 5 ]

echo "$COUNTER"

COUNTER=$((COUNTER + 1))

done

# Conditional statement

if [ $COUNTER -gt 5 ]; then

echo "Count complete!"

else

echo "Count failed."

**\>> Explanation for above script:

#!/bin/bash -** This line indicates that the script should be run using the Bash shell.

USER_NAME="User"

GREETING="Hello"

COUNTER=1

These lines define three variables:

USER_NAME is set to "User".
GREETING is set to "Hello".
COUNTER is initialized to 1.

# Greeting the user

echo "$GREETING, $USER_NAME!"

This line outputs a greeting message to the user by combining the GREETING and USER_NAME variables. It will display: Hello, User!

# Loop to count from 1 to 5

echo "Counting from 1 to 5:"

while [ $COUNTER -le 5 ]

echo "$COUNTER"

COUNTER=$((COUNTER + 1))

done

This section starts a loop:

- It first prints "Counting from 1 to 5:".
  - The while loop checks if COUNTER is less than or equal to 5 (-le stands for "less than or equal").
  - Inside the loop:

- - It prints the current value of COUNTER.
    - It increments COUNTER by 1 using the expression COUNTER=$((COUNTER + 1)).

The loop continues until COUNTER exceeds 5, resulting in the numbers 1 to 5 being printed.

# Conditional statement

if [ $COUNTER -gt 5 ]; then

echo "Count complete!"

else

echo "Count failed."

This part contains a conditional statement:

- The if checks if COUNTER is greater than 5 (-gt stands for "greater than").
  - Since the loop increments COUNTER to 6 after counting to 5, the condition will be true.
  - If true, it prints "Count complete!".
  - If never true (which in this script will not happen), it would print "Count failed."
  \==================================================**

**// Here we can use -p (prompt)//

vi prompt.sh

#!/bin/bash**

# This script is used for reading variables.

# Prompt for the first name

read -p "Enter your name: " name

echo "My name is $name"

# Prompt for the second name

echo "What is your name?"

read name2

echo "My name is $name2"

Outputs :

oot@Scripting:/home/ubuntu/scripting# ./prompt.sh**

Enter your name: Rajan

My name is Rajan

What is your name?

aadu

My name is aadu

**
\===========================================================
// Below script will install NGINX and enable it also //

#!/bin/bash

<<Note

This script will install NGINX.

Note

echo "******************************************Installing_NGINX*****************************************"

sudo apt-get update

sudo apt-get install nginx -y

sudo systemctl start nginx

sudo systemctl enable nginx

echo "***********************************Installation_Complete*******************************************"

sudo nginx -v

**\=========================================================
//Arguments : We can pass any arguments //

#!/bin/bash**

# This script will install any package.

# Usage: ./Install_package.sh <package-name>

# Check if a package name is provided

if [ -z "$1" ]; then

echo "Error: No package name provided."

echo "Usage: ./Install_package.sh <package-name>"

exit 1

# Display the package name provided

echo "Package to install: $1"

# Start installation process

echo "******************** Installing $1 ********************************"

# Update package list

sudo apt-get update

# Install the package

sudo apt-get install "$1" -y

# Start the service (if it has a service associated with it)

sudo systemctl start "$1"

# Enable the service to start on boot

sudo systemctl enable "$1"

# Installation complete

echo "********************** $1 Installed Successfully **********************************"

**\===========================================================

#!/bin/bash**

<<disclaimer

Is kahani ke sabhi patr and Ghatnaye kalpnic

disclaimer

read -p "Enter Gabbar's Dilogue:" gb

read -p "Enter Thakur's Dilogue:" th

echo "$gb"

**echo "$th"

Output :

root@ip-172-31-45-40:~/Scripts# ./Gabbar_Thakur.sh**

Enter Gabbar's Dilogue:ye hath hmko de thakur

Enter Thakur's Dilogue:Nahi

ye hath hmko de thakur

**Nahi

\===========================================================**

**// Conditional Statement If and Else //

\>> If and Else are conditional statements ;

\>> scripts below :

#!/bin/bash**

<<disclaimer

Iss kahani ke sabhi patr and ghatnaye kalpnic hai

disclaimer

read -p "Enter gabbar's dialogoue" gb

read -p "Enter Thakur's dialogue" th

echo "$gb"

echo "$th"

if [[ $th == "nahi" ]];

then

echo "Jai veeru ki entry and bhsad"

else

echo "chop chop"

**echo "sholay kahtam"

**\===========================================================
// Process for take the BKP //

./Install-pkg.sh zip - For install the zip

zip -r backup.zip /home/ubuntu/script - This will compress the script and store in backup.zip

\===========================================================

// Below script will show date in format and take bakup.//

#!/bin/bash**

<<Note

This will take backup of any destination path given in arguments

./backup.sh /home/ubuntu/script

Note

**echo "$(date '+%Y-%m-%d')"

Output :

root@shellMachine:/home/ubuntu/script# ./backup.sh**

2024-12-02

\===========================================================

**//Below script will take the backup with timestamp //

vi backup.sh

#!/bin/bash**

<<Note

This will take backup of any destination path given in arguments

./backup.sh /home/ubuntu/script

Note

timestamp="$(date '+%Y-%m-%d-%H-%M-%S')"

backup_dir="${timestamp}_backup.zip"

zip -r $backup_dir $1

echo "Backup complete"

**output :

\==========================================================

//CRONE //

\>> Use this website for use the crone in better way - [crontab.guru/#5_4_*_*_1*](crontab.guru/#54_*_1)

#!/bin/bash

<<Note

This will take backup of any destination path given in arguments

./backup.sh /home/ubuntu/script

Note

function show_date {

echo "Today is : $(date '+%Y-%m-%d-%H-%M-%S')"

}

function create_backup {

timestamp="$(date '+%Y-%m-%d-%H-%M-%S')"

backup_dir="/home/ubuntu/backups${timestamp}_backup.zip"

zip -r $backup_dir $1

echo "Backup complete"

}

show_date

**create_backup