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Shell Introduction

  • Study of Shell, Types of Shell, Variables and Operators
  • Write a shell script to perform arithmetic operations
  • Write a shell script to calculate simple interest
  • Write a shell script to determine largest among three integer numbers
  • Write a shell script to determine a given year is leap year or not
  • Write a shell script to print multiplication table of given number using while statement
  • Write a shell script to search whether element is present is in the list or not
  • Write a shell script to compare two strings
  • Write a shell script to read and check if the directory / file exists or not, if not make the directory / file
  • Write a shell script to implement menu-driven calculator using case statement.

  • Write a shell script to print following pattern:

    *

    * *

    * * * *

    * * * * *

1. Shell Script to perform Arithmatic Operations using expr

#!/bin/sh

a=10
b=20

val=`expr $a + $b`
echo "a + b : $val"

val=`expr $a - $b`
echo "a - b : $val"

val=`expr $a \* $b`
echo "a * b : $val"

val=`expr $b / $a`
echo "b / a : $val"

val=`expr $b % $a`
echo "b % a : $val"

if [ $a == $b ]
then
  echo "a is equal to b"
fi

if [ $a != $b ]
then
  echo "a is not equal to b"
fi

2. Shell Script to perform Arithmatic Operations using Double Parenthesis

#!/bin/bash

x=10
y=3

echo $(( x + y ))   # addition
echo $(( $x + $y )) # also valid

echo $(( x - y ))   # subtraction
echo $(( $x - $y )) # also valid

echo $(( x * y ))   # multiplication
echo $(( $x * $y )) # also valid

echo $(( x / y ))   # division
echo $(( $x / $y )) # also valid

echo $(( x ** y ))  # exponentiation
echo $(( $x ** $y ))    # also valid

echo $(( x % y ))   # modular division
echo $(( $x % $y )) # also valid

(( x += 4 ))    # increment variable by constant
echo $x

(( x -= 4 ))    # decrement variable by constant 
echo $x

(( x *= 4 ))    # mulitply variable by constant
echo $x

(( x /= 4 ))    # divide variable by constant
echo $x

(( x %= 4 ))    # Remainder of Dividing Variable by Constant
echo $x

3. Shell Script to perform Arithmatic Operations using let

#!/bin/bash

x=10
y=3
z=0

let "z = $(( x + y ))"  # addition
let z=$((x+y))  # also valid without double quotes when no spaces in expression
echo $z

let "z = $(( x - y ))"  # subtraction
let z=$((x-y))
echo $z

let "z = $(( x * y ))"  # multiplication
let z=$((x*y))
echo $z

let "z = $(( x / y ))"  # division
let z=$((x/y))
echo $z

let "z = $(( x ** y ))" # exponentiation
let z=$((x**y))
echo $z

let "z = $(( x % y ))"  # modular division
let z=$((x%y))
echo $z

let "x += 4"    # increment variable by constant
echo $x

let "x -= 4"    # decrement variable by constant 
echo $x

let "x *= 4"    # mulitply variable by constant
echo $x

let "x /= 4"    # divide variable by constant
echo $x

let "x %= 4"    # Remainder of Dividing Variable by Constant
echo $x

4. Write a shell script to calculate simple interest

echo " Enter the principle value: "
read p
echo " Enter the rate of interest:"
read r
echo " Enter the time period:"
read t
s=`expr $p \* $t \* $r / 100`
echo " The simple interest is "
echo $s

5. Write a shell script to determine largest among three integer numbers

echo "Enter the 1st Number: "
read n1
echo "Enter the 2nd Number: "
read n2
echo "Enter the 3rd Number: "
read n3

total=`expr $n1 + $n2 + $n3`
avg=`expr $total / 3`

if [ $n1 -gt $n2 -a $n1 -gt $n3 ]
then
echo "$n1 is the Largest of three"
elif [ $n2 -gt $n1 -a $n2 -gt $n3 ]
then
echo "$n2 is the Largest of three"
elif [ $n3 -gt $n1 -a $n3 -gt $n2 ]
then
echo "$n3 is the Largest of three"
else
echo "All the three numbers are Equal"
fi
echo "Total: $total"
echo "Average: $avg"

6. Write a shell script to determine a given year is leap year or not

echo "Enter the year in 4 digits: "
read num
if [ $num -ge 1000 -a $num -le 9999 ]
then
if [ `expr $num % 4` -eq 0 ]
then
echo "The year $num is a Leap year"
else
echo "The year $num is not a Leap year"
fi
else
echo "Invalid year format"
fi

7. Write a shell script to print multiplication table of given number using while statement

Usng Expr clear echo "which number to generate multiplication table" read number i=1 while [ $i -le 10 ] do echo " $number * $i =expr $number \* $i " i=expr $i + 1 done

Using double parentheses

echo "Enter a Number" read n i=1

while [ $i -le 10 ] do echo " $n x $i = $(( n * i ))" i=$(( i + 1 )) done

8. Write a shell script to search whether element is present is in the list or not

#!/bin/bash task=$1 arr=("task1" "task2" "task3") if [[ " ${arr[@]} " =~ " ${task} " ]]; then echo "User has provided correct $task in argument" echo "Put your logic for $task"

else echo "Please pass correct task name in argument" echo "Correct values are" echo '("task1" "task2" "task3")' fi

Write a shell script to implement menu-driven calculator using case statement.

# !/bin/bash # Take user Input echo "Enter Two numbers : " read a read b

# Input type of operation echo "Enter Choice :" echo "1. Addition" echo "2. Subtraction" echo "3. Multiplication" echo "4. Division" read ch

# Switch Case to perform # calculator operations case $ch in 1)res=echo $a + $b | bc ;; 2)res=echo $a - $b | bc ;; 3)res=echo $a \* $b | bc ;; 4)res=echo "scale=2; $a / $b" | bc ;; esac echo "Result : $res"

10. Shell Script to print half pyramid using *

rows=4
for((i=1; i<=rows; i++))
do
  for((j=1; j<=i; j++))
  do
    echo -n "* "
  done
  echo
done

11.

#! /bin/bash -
if [[ ! -e /Scripts/file.txt ]]; then
    mkdir -p /Scripts
    touch /Scripts/file.txt
fi


if [ -f /etc/resolv.conf -a -f /etc/hosts ]; then
    echo "Both files exist."
fi


FILE=/etc/resolv.conf
if [ -f "$FILE" ]; then
    echo "$FILE exists."
else 
    echo "$FILE does not exist."
fi

$ [[ -d /var/logs ]] && echo "Directory exist" || echo "Directory does not exist" $ [[ -d /dumper/fake ]] && echo "Directory exist" || echo "Directory does not exist"

Shell script to compare two strings

## Example 1 

#!/bin/bash

VAR1="Linuxize"
VAR2="Linuxize"

if [ "$VAR1" = "$VAR2" ]; then
    echo "Strings are equal."
else
    echo "Strings are not equal."
fi

#!/bin/bash

## Example 2

read -p "Enter a string: " str1

if [ $str1 == "linux" ] then echo "linux" elif [ $str1 == "unix" ] then echo "unix" else echo "Neither linux nor unix" fi

## Example 3

read -p "Enter first string: " VAR1 read -p "Enter second string: " VAR2

if [[ "$VAR1" == "$VAR2" ]]; then echo "Strings are equal." else echo "Strings are not equal." fi