Basic Of Shell Scripting -Part 2

If Statement:
We use the "if statement" for checking the condition. If we have multiple conditions we can also use multiple "if statements".
Syntax:

if [ expression ]
then
   statement
fi

Example For If Statement:

#!/bin/bash
a=5
b=30

if [ $a -lt $b ]
then
        echo "a is less than b"
fi

if - else statement
Syntax

if [ expression ]
then
   statement1
else
   statement2
fi

Example For If -else Statement:

#!/bin/bash
a=5
b=30

if [ $a -lt $b ]
then
        echo "a is less than b"
else
        exho "b is less than a"
fi

Multiple If-Else Statement
Syntax

if [ expression1 ]
then
   statement1
   statement2
   .
   .
elif [ expression2 ]
then
   statement3
   statement4
   .
 eg.Syntax  .
else
   statement5
fi

Example For Multiple If -else Statement:

#!/bin/bash

echo "enter the color"
read color

if [ ${color} == "Red" ]
then
   echo "You have enter Red Color"
elif [ ${color} == "Blue" ]
then
   echo "You have enter Blue Color"
else
   echo "Color is Neither the blue one nor the red one"
fi

Nested if-Else statement:
Syntax:

if [ expression1 ]
then
   statement1
   statement2
   .
else
   if [ expression2 ]
   then
      statement3
      .
   fi
fi

Example For Nested If -else Statement:

#!/bin/bash

echo "enter the color"
read color
echo "enter the car name"
read car
if [ ${color} == "Red" ]
then
   echo "You have selected red color"
   if [ ${car} == "BMW" ]
   then
        echo " You have selected Red BMW"
   fi
elif [ ${color} == "Green" ]
then
   echo "You have selected Green color"
   if [ ${car} == "Audi" ]
   then
        echo " You have selected Green Audi"
   fi
else
    echo "Wrong Input"
fi