Decision Making Statements: -

Q) What are decision making statements ?

Ans – There are two decision making statements. Such as –

1.       If else fi

2.       case esac

Q) Write a shell script whether a given number will be even or odd ?

Ans –

#! /bin/sh

echo “Enter a number: “

read n

if [ `expr $n % 2` -eq 0 ]

then

echo “$n is even number”

else

echo “$n is odd number”

fi

Q) Take two numbers from command line and check which is greater ?

Ans –

$ vi script7.sh

#! /bin/sh

If [ $1 –gt $2 ]

then

echo “$1 is greater than $2”

else

echo “$2 is greater than $1”

fi

ESC + :wq<Enter – Key>

$ chmod 755 script7.sh

$ ./script7.sh 23 45<Enter – Key>

Output –

45 is greater than 23

Q) Take two numbers as user input. Get the summation of it, if sum is greater than 10, then multiply it with 2 else multiply it with 3 and display the result ?

Ans –

#! /bin/sh

echo “Enter two numbers: “

read a b

s=`expr $a + $b`

if [ $s –gt 10 ]

then

echo “Result = `expr $s \* 2`”

else

echo “Result = `expr $s \* 3`”

fi

Q) Write a script to swap two numbers without help of third variable ?

Ans –

#! /bin/sh

echo “Enter two numbers: “

read a b

echo “Before swapping a = $a and b = $b”

a=`expr $a + $b`

b=`expr $a - $b`

a=`expr $a - $b`

echo “After swapping a = $a and b = $b”

Q) Write a script to swap two numbers with help of third variable ?

Ans - 

#! /bin/sh

echo “Enter two numbers: “

read a b

echo “Before swapping a = $a and b = $b”

c=$a

$a=$b

$b=$c

echo “After swapping a = $a and b = $b”

Q) What are syntax of different if else fi statements ?

Ans –

Simple IF:

If [ Condition ]

then

statements

fi

IF ELSE FI:

If [ Condition ]

then

statements

else

statements

fi

Nested IF:

If [ Condition ]

then

statements

                     If [ Condition ]

                     then

                     statements

                     else

                     statements

                     fi

else

statements

                     If [ Condition ]

                     then

                     statements

                     else

                     statements

                     fi

fi

ELSE IF LADDER:

If [ Condition ]

then

statements

elif [ Condition ]

then

statements

elif [ Condition ]

then

statements

else

statements

fi

Q) What is the syntax of case esac statements ?

Ans –

case variable in

Value1)

echo “Statements”

;;

Value2)

echo “statements”

;;

0)

exit

;;

esac

Q) Write a script to know case esac statements ?

Ans –

#! /bin/sh

echo “Enter the state name or zero to exit: “

read state

case $state in

“Odisha”)

echo “Bhubaneswar”

;;

“Karnataka”)

echo “Bengaluru”

;;

0)

exit

;;

esac

Q) What are shell loops ?

Ans –

1.       while

2.       until

3.       for

4.       select

Q) What is the syntax of while loops ?

Ans –

while [ Condition ]

do

statements

done

Part – 1: -

Q) Write a script to print 1 to 10 ?

Ans –

#! /bin/sh

i=1

while [ $i –le 10 ]

do

echo “$i”

i=`expr $i + 1`

done

Q) Write a script to print all even numbers between 50 to 100 ?

Ans –

#! /bin/sh

i=50

while [ $i –le 100 ]

do

echo “$i”

i=`expr $i + 2`

done

Q) Print first 10 even numbers ?

Ans –

#! /bin/sh

i=1

count = 1

while [ $count –le 10 ]

do

echo “`expr $i \* 2`”

count=`expr $count + 1`

i=`expr $i + 1`

done

Q) Write a script to know whether a number is prime or not ?

Ans –

echo “Enter a number: “

read num

i=1

count=0

while [ $i –le $num ]

do

if [ `expr $num % $i` -eq 0 ]

then

count=`expr $count + 1`

fi

i=`expr $i + 1`

done
if [ $count –eq 2 ]

then

echo “$num is a prime number”

else

echo “$num is not a prime number”

fi

Q) Check whether a number is palindrome or not ?

Ans –

#! /bin/sh

echo “Enter a number: “

read num

i=0

j=$num

while [ $j –gt 0 ]

do

rem=`expr $j % 10`

i=`expr $i \* 10 + $rem`

j=`expr $j / 10`

done

if [ $i –eq $num ]

then

echo “$num is a palindrome number”

else

echo “$num is not a palindrome number”

fi