Bash If-elif-else-fi

Example 1

#! /bin/bash 

#this program gets two numbers from the user and compare them  
 

read -p "Enter two numbers : " num1 num2 

echo "The numbers are $num1 and $num2" 

if [ "$num1" -eq "$num2" ]; then 

        echo "the numbers are equal" 

elif [ $num1 -gt $num2 ]; then 

        echo "num1 is greater than num2" 

else 

        echo "num1 is less than num2" 

fi 

Example 2

 


#! /bin/bash 

if [ -z $1 ]; then 

        echo "Error: filename not given" 

        echo "This utility backups a given file with an extension .bk"  

        echo "Usage: if-demo.sh " 

        exit 1 

elif [ -d $1 ]; then 

        echo "Error: " 

        echo "directory found, instead of a file. This utility does not backup directory" 

        exit 1 

fi 

cp "$1" "$1.bk" 

Another example

 

#! /bin/bash 
  

read -p "Enter the age" age 

read -p "Enter the price" price 

  

if [ $age -gt 65 ]; then 

        echo "Senior discount is applied."  

        echo "Please pay:" 

        echo "scale=2; $price*0.95" | bc 

elif [ $age -gt 17 ]; then  

        echo "Please pay: $price" 

else  

        echo "You cannot alcohol" 

fi