Bash Shell Scripts

Q.1. How to write shell script that will add two nos, which are supplied
 as command line argument, and if this two nos are not given show error 
and its usage 

#!/bin/bash
# Q1.Script to sum to nos
#

if [ $# -ne 2 ]
then
    echo "Usage - $0   x    y"
    echo "        Where x and y are two nos for which I will print sum"
    exit 1
fi
    echo "Sum of $1 and $2 is `expr $1 + $2`"
#
 

Q.2.Write Script to find out biggest number from given three nos. Nos 
are supplies as command line argument. Print error if sufficient 
arguments are not supplied.

#!/bin/bash
# Q2. Script to find out bigest number
#
# Algo:
#      1) START: Take three nos as n1,n2,n3.
#      2) Is n1 is greater than n2 and n3, if yes 
#         print n1 is bigest no goto step 5, otherwise goto next step
#      3) Is n2 is greater than n1 and n3, if yes 
#         print n2 is bigest no goto step 5, otherwise goto next step
#      4) Is n3 is greater than n1 and n2, if yes 
#         print n3 is bigest no goto step 5, otherwise goto next step
#      5) END
#
#

    if [ $# -ne 3 ]
    then
 echo "$0: number1 number2 number3 are not given" >&2
        exit 1    
    fi
    n1=$1
    n2=$2
    n3=$3
    if [ $n1 -gt $n2 ] && [ $n1 -gt $n3 ]
    then
 echo "$n1 is Bigest number"
    elif [ $n2 -gt $n1 ] && [ $n2 -gt $n3 ]         
    then
 echo "$n2 is Bigest number"
    elif [ $n3 -gt $n1 ] && [ $n3 -gt $n2 ]         
    then
        echo "$n3 is Bigest number"
    elif [ $1 -eq $2 ] && [ $1 -eq $3 ] && [ $2 -eq $3 ]
    then
 echo "All the three numbers are equal"    
    else
        echo "I can not figure out which number is biger"    
    fi    

 

Q.3.Write script to print nos as 5,4,3,2,1 using while loop.

#!/bin/bash
# Q3
# Algo:
#       1) START: set value of i to 5 (since we want to start from 5, if you
#          want to start from other value put that value)
#       2) Start While Loop
#       3) Chechk, Is value of i is zero, If yes goto step 5 else
#          continue with next step
#       4) print i, decement i by 1 (i.e. i=i-1 to goto zero) and
#          goto step 3
#       5) END
#
i=5
while test $i != 0
do
 echo "$i
"
 i=`expr $i - 1`
done
 

Q.4. Write Script, using case statement to perform basic math operation as
 follows
 + addition
 - subtraction
 x multiplication
 / division
 The name of script must be 'q4' which works as follows
 $ ./q4 20 / 3, Also check for sufficient command line arguments

#!/bin/bash
# Q4
#

if test $# = 3
then
 case $2 in
  +) let z=$1+$3;;
  -) let z=$1-$3;;
  /) let z=$1/$3;;
  x|X) let z=$1*$3;;
  *) echo Warning - $2 invalied operator, only +,-,x,/ operator allowed
     exit;;
 esac
 echo Answer is $z
else
 echo "Usage - $0   value1  operator value2"
 echo "        Where, value1 and value2 are numeric values"
 echo "               operator can be +,-,/,x (For Multiplication)"
fi



 

Q.5.Write Script to see current date, time, username, and current directory

#!/bin/bash
# Q5

echo "Hello, $LOGNAME"
echo "Current date is `date`"
echo "User is `who i am`"
echo "Current direcotry `pwd`"


 

Q.6.Write script to print given number in reverse order, for eg. If no is 123 it must print as 321.

#!/bin/bash
# Script to reverse given no
#
# Algo:
#       1) Input number n
#       2) Set rev=0, sd=0
#    3) Find single digit in sd as n % 10 it will give (left most digit)
#       4) Construct revrse no as rev * 10 + sd
#       5) Decrment n by 1
#       6) Is n is greater than zero, if yes goto step 3, otherwise next step
#       7) Print rev
#
if [ $# -ne 1 ]
then
    echo "Usage: $0   number"
    echo "       I will find reverse of given number"
    echo "       For eg. $0 123, I will print 321"
    exit 1
fi

n=$1
rev=0
sd=0

while [ $n -gt 0 ]
do
    sd=`expr $n % 10`
    rev=`expr $rev \* 10  + $sd`
    n=`expr $n / 10`
done
    echo  "Reverse number is $rev"