Shell Programming - Control Structures

SHELL PROGRAMMING

// Shell programs

// IF STATEMENT

// Even or Odd

echo -n "Enter a number : "

read n

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

then

echo "$n is Even"

else

echo "$n is Odd"

fi      

// Positive negative or zero

echo -n "Hello "; logname

echo -n "enter a number : "

read a

if [ $a -lt 0 ]

then

echo " $a is negetive"

elif [ $a -gt 0 ]

then

echo "$a is Positive"

else

echo "$a is Zero"

fi

// Biggest if three numbers

echo -n "Enter three numbers : "

read a b c

if [ $a -gt $b ]

then

if [ $a -gt $c ]

then

echo "Biggest is $a"

else

echo "Biggest is $c"

fi

else

if [ $b -gt $c ]

then

echo "Biggest is $b"

else

echo "Biggest is $c"

          fi

fi

//SWITCH STATEMENTS

// Arithmetic Operations

echo "Menu"

echo "1 - Addition"

echo "2 - Subtraction"

echo "3 - Multiplication"

echo "4 - Division"

echo -n "Enter your choice : "

read n

echo -n "Enter the numbers : "

read a b

case $n in

1) echo "Sum of $a and $b is `expr $a + $b`";;

2) echo "Difference of $a and $b is `expr $a - $b`";;

3) echo "Product of $a and $b is `expr $a \* $b`";;

4) echo "Division of $a by $b is `expr $a / $b`";;

*) echo "Invalid choice";;

esac

// Number – words

echo -n "Enter the number less than 10 : "

read n

case $n in

1) echo "$n - ONE";;

2) echo "$n - TWO";;

3) echo "$n - THREE";;

4) echo "$n - FOUR";;

5) echo "$n - FIVE";;

6) echo "$n - SIX";;

7) echo "$n - SEVEN";;

8) echo "$n - EIGHT";;

9) echo "$n - NINE";;

0) echo "$n - ZERO";;

*) echo "Invalid choice";;

esac

//WHILE LOOP

// Squares and Cubes up to given number

echo -n "Enter a number : "

read n

echo -e "\t Number \t Square \t Cube"

i=1

while [ $i -le $n ]

do

sq=`expr $i \* $i`

cu=`expr $i \* $sq`

echo -e "\t $i \t\t $sq \t\t $cu "

i=`expr $i + 1`

done

// Reverse a number

echo -n "Enter a number : "

read n

ori=$n

i=0

while [ $n -gt 10 ]

do

mod=`expr $n % 10`

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

n=`expr $n / 10`

done

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

echo "Entered Number : $ori"

echo "Reversed Number : $i"

// Number of digits

echo -n "Enter a number : "

read n

i=1

while [ $n -gt 10 ]

do

n=`expr $n / 10`

i=`expr $i + 1`

done

echo “Number of digits is $i”

// FOR LOOP

// Read and display array.

// Find biggest and smallest in array

echo "Enter 5 values : "

for i in 0 1 2 3 4

do

read a[$i]

done

echo "Entered values are "

for (( i=0; i<5; i++))

do

echo -e "\t ${a[$i]}"

done

big=${a[0]}

small=${a[0]}

for ((i=1;i<5;i++))

do

if [ $big -lt ${a[i]} ]

then

     big=${a[$i]}

fi

if [ $small -gt ${a[$i]} ]

then

     small=${a[$i]}

fi

done

echo "Biggest is $big"

echo "Smallest is $small"

// Sorting 5 numbers

echo "Enter 5 values : "

for i in 0 1 2 3 4

do

read a[$i]

done

echo "Entered Values are "

for (( i=0; i<5; i++))

do

echo -e "\t ${a[$i]}"

done

// Sorting loop

for ((i=0;i<4;i++))

do

for ((j=`expr $i + 1`; j<5;j++))

do

if [ ${a[$j]} -lt ${a[i]} ]

then

t=${a[$i]}

          a[$i]=${a[$j]}

          a[$j]=$t

fi

done

done

// Output

echo "Sorted Numbers : "

for ((i=0;i<5;i++))

do

echo -e "\t ${a[$i]}"

done