Shell Script to swap values in two variables x and y

in Categories Shell Math last updated April 9, 2008
#!/bin/bash
# Shell Script to swap values in two variables x and y
# -------------------------------------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
echo "Enter value for x : "
read x
echo "Enter value for y : "
read y
echo "Before swap, x = $x and y = $y"
z=$x
x=$y
y=$z
echo "After swap, x = $x and y = $y"

Shell script to find whether an input number is palindrome or not

in Categories Academic, Shell Math last updated April 12, 2008

A palindrome is a word, phrase, number or other sequence of units that has the property of reading the same in either direction (the adjustment of punctuation and spaces between words is generally permitted). Composing literature in palindromes is an example of constrained writing. The word “palindrome” was coined from Greek roots palin (“back”) and dromos (“way, direction”) by English writer Ben Jonson in the 1600s.

A palindromic number is a number where the digits, with decimal representation usually assumed, are the same read backwards, for example, 58285. They are studied in recreational mathematics where palindromic numbers with special properties are sought. A palindromic prime is a palindromic number that is a prime number.

#!/bin/bash
# Shell script to find whether an input number is palindrome or not
# -----------------------------------------------
# Copyright (c) 2006 nixCraft <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
echo -n "Enter number : "
read n
 
# store single digit
sd=0
 
# store number in reverse order
rev=""
 
# store original number
on=$n
 
while [ $n -gt 0 ]
do
    sd=$(( $n % 10 )) # get Remainder 
    n=$(( $n / 10 ))  # get next digit
    # store previous number and current digit in reverse 
    rev=$( echo ${rev}${sd} ) 
done
 
if [ $on -eq $rev ];
then
  echo "Number is palindrome"
else
  echo "Number is NOT palindrome"
fi

Shell program to read a number and reverse the number

in Categories Academic, Shell Math last updated April 8, 2008
#!/bin/bash
# Shell program to read a number and reverse the number
# for example 123 should output as 321
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
echo -n "Enter number : "
read n
 
# store single digit
sd=0
 
# store number in reverse order
rev=""
 
# store original number
on=$n
 
# use while loop to caclulate the sum of all digits
while [ $n -gt 0 ]
do
    sd=$(( $n % 10 )) # get Remainder 
    n=$(( $n / 10 ))  # get next digit
    # store previoues number and current digit in rev
    rev=$( echo ${rev}${sd} ) 
done
 
echo  "$on in a reverse order $rev"

Shell program to calculate the number of digits in a number read from the user

in Categories Academic, Shell Math last updated April 8, 2008
#!/bin/bash
# Shell program to calculate the number of digits in a
# number read from the user
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
echo -n "Enter number : "
read n
 
sd=0
 
# store number of digit 
nd=0
on=$n # store $n so that we can use it later
 
# use while loop to caclulate the number of digit
while [ $n -gt 0 ]
do
    sd=$(( $n % 10 )) # get Remainder 
    n=$(( $n / 10 )) 
    nd=$(( $nd + 1)) # calculate all digit in a number till n is not zero
done
echo  "Numnber of digit in a $on is $nd"

Shell program to display numbers from 1 to 10

in Categories Academic last updated April 8, 2008
#!/bin/bash
# Shell program to display numbers from 1 to 10
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
# using for loop
echo "Using for loop method # 1... "
for i in 1 2 3 4 5 6 7 8 9 10
do
  echo -n "$i " 
done
echo ""
 
# this is much better as compare to above for loop
echo "Using for loop method # 2... "
for (( i=1; i<=10; i++ ))
do
   echo -n "$i "
done
echo ""
 
# use of while loop
echo "Using while loop..."
j=1
while [ $j -le 10 ]
do
   echo -n "$j "
   j=$(( j + 1 )) # increase number by 1 
done
echo ""

Shell Script to read any year and find whether it is a leap year or not

in Categories Time and Date last updated April 5, 2008

A leap year comes once every four years. It is the year when an extra day is added to the Gregorian calendar used by most of the world.

An ordinary year has 365 days. A leap year has 366 days. The extra day is added to the month of February. In an ordinary year, February has 28 days. In a leap year, it has 29 days. This extra day is called a leap day.

How do I find out leap year?

A year is a leap year if it can be evenly divided by four. For example, 1996 was a leap year. But a year is not a leap year if can be evenly divided by 100 and not by 400. This is why 1700, 1800, 1900 were not leap years, but 2000 was.

Shell script to determine if entered year is leap or not…

#!/bin/bash
# Shell program to read any year and find whether leap year or not
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
# store year
yy=0
isleap="false"
 
echo -n "Enter year (yyyy) : "
read yy
 
# find out if it is a leap year or not
 
if [ $((yy % 4)) -ne 0 ] ; then
   : #  not a leap year : means do nothing and use old value of isleap
elif [ $((yy % 400)) -eq 0 ] ; then
   # yes, it's a leap year
   isleap="true"
elif [ $((yy % 100)) -eq 0 ] ; then
   : # not a leap year do nothing and use old value of isleap
else
   # it is a leap year
   isleap="true"
fi
if [ "$isleap" == "true" ];
then
   echo "$yy is leap year"
else
   echo "$yy is NOT leap year"
fi

Shell Script to find the validity of a given date

in Categories Time and Date last updated April 5, 2008

Date is entered in mm/dd/yyyy format using a keyboard. Various conditions are applied to make sure date is valid. Read the program comments to get idea about program logic.

#!/bin/bash
# Shell program to find the validity of a given date
# -----------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
# store day, month and year
dd=0
mm=0
yy=0
 
# store number of days in a month
days=0
 
# get day, month and year
echo -n "Enter day (dd) : "
read dd
 
echo -n "Enter month (mm) : "
read mm
 
echo -n "Enter year (yyyy) : "
read yy
 
# if month is negative (<0) or greater than 12 
# then it is invalid month
if [ $mm -le 0 -o $mm -gt 12 ];
then
    echo "$mm is invalid month."
    exit 1
fi
 
# Find out number of days in given month
case $mm in 
    1) days=31;;
    2) days=28 ;;
    3) days=31 ;;
    4) days=30 ;;
    5) days=31 ;;
    6) days=30 ;;
    7) days=31 ;;
    8) days=31 ;;
    9) days=30 ;;
    10) days=31 ;;
    11) days=30 ;;
    12) days=31 ;;
    *) days=-1;;
esac
 
# find out if it is a leap year or not
 
if [ $mm -eq 2 ]; # if it is feb month then only check of leap year
then
	if [ $((yy % 4)) -ne 0 ] ; then
	   : #  not a leap year : means do nothing and use old value of days
	elif [ $((yy % 400)) -eq 0 ] ; then
	   # yes, it's a leap year
	   days=29
	elif [ $((yy % 100)) -eq 0 ] ; then
	   : # not a leap year do nothing and use old value of days
	else
	   # it is a leap year
	   days=29
	fi
fi
 
# if day is negative (<0) and if day is more than 
# that months days then day is invaild
if [ $dd -le 0 -o $dd -gt $days ];
then
    echo "$dd day is invalid"
    exit 3
fi
 
# if no error that means date dd/mm/yyyy is valid one
echo "$dd/$mm/$yy is a vaild date"

Shell script to read a number and find whether the number is odd or even

in Categories Decision Making last updated April 5, 2008
#!/bin/bash
# Shell script to read a number and find whether the number is odd or even
# -------------------------------------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
echo -n "Enter numnber : "
read n
 
rem=$(( $n % 2 ))
 
if [ $rem -eq 0 ]
then
  echo "$n is even number"
else
  echo "$n is odd number"
fi

Shell script to read 5 digit number and calculate the sum of digit

in Categories Shell Math last updated April 4, 2008
#!/bin/bash
# Shell script to read 5 digit number and calculate the sum of digit
# -------------------------------------------------------------------------
# Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
echo -n "Enter numnber : "
read n
 
# find out length of string using wc -c command
len=$(echo $n | wc -c)
 
# remove \n i.e. new line character
len=$(( $len - 1 ))
 
# use loop to go throug all digit one by one and calculate sum of digit on fly
for (( i=1; i <= $len; i++ ))
do
   sum=$(( $sum + $(echo $n | cut -c $i) ))
done
echo "Sum of $n is $sum"