Example

#Program for Arithmetic Operations
#!/bin/bash
#Author : Antony
#Date : 05/10/2007
 
echo "Enter the first Number "
read x
echo "Enter the second Number "
read y
#Method 1
add=<span style="font-weight: bold; font-style: italic;">$(( $x + $y ))</span>
echo "The Addition is $add"
 
#Method 2
sub=<span style="font-weight: bold; font-style: italic;">`expr $x - $y`</span>
echo "The Subtraction is $sub"
 
#Method 3
div=<span style="font-weight: bold; font-style: italic;">`echo "scale=4; $x / $y" | bc`</span>
echo "The Divison is $div"

Output of this program

VIT:/home/antony# sh arith.sh
Enter the first Number
123
Enter the second Number
124
The Addition is 247
The Subtraction is -1
The Divison is .9919
VIT:/home/antony#

echo “Enter the text “
read text
tput bold
echo $text
tput reset

Output of this Program
Enter the text

Antony

Antony

x=1
while [ ! $x -ge 5 ]
do
echo $x
x=`echo “$x+1″ | bc`
done

y=1
until [ $y -ge 5 ]
do
echo $y
y=`echo “$y+1″ | bc`
done

#Simple Example
echo “Select the Option”
echo “1.Terminal”
echo “2.Firefox”
echo “3.Text editor”

read name

case $name in
1) echo “Terminal is running…”
echo “`xterm`” ;;
2) echo “Firefox is running…”
echo “`firefox`” ;;
3) echo “Text editor has been opened …”
echo “`gedit`” ;;
esac

#Three Types of quotes are
# 1.Single quote
# 2.Double quote
# 3.Backslash

#Examples

echo “Current Date is `date`”

echo This \’song\’ is so nice

echo The Movie \”Gladiator\” won 7 oscar awards
echo ‘The total amount is $10000′

echo “The total amount is \$1000″

echo “Wow! This is so beautiful…”

echo Hello Ram\; How are you?

#Output of this program
# Current Date is Fri Jul 27 07:00:58 IST 2007
# This ‘song’ is so nice
# The Movie “Gladiator” won 7 oscar awards
# The total amount is $10000
# The total amount is $1000
# Wow! This is so beautiful…
# Hello Ram; How are you?

#Indicates the Current working directory
echo “The Current Working directory is $PWD”

# Display User ID
echo “Current User ID is $UID”

#Generating random integers between 1 and 32767
echo “The random number is $RANDOM”

#Information about path
echo “The Path details”
echo $PATH

#Home Directory information
echo “Your Home directory is $HOME”

#Output of this program

# [rooot@netadmin /]# sh envvardemo3.sh
# The Current Working directory is /
# Current User ID is 0
# The random number is 28804
# The Path details
# /usr/java/jdk1.6.0/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/java/jdk1.6.0/bin:
# /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin
# Your Home directory is /root

#Two types of variables
# 1. Scalar variables/name value pairs
# 2. Array Variables

# 1.Scalar variables
var=”This is the Demo Program for Variables”

#To diplay the variable content
#prefix variable name with $ symbol and use echo

echo $var

# 2.Array Variables
# The Syntax is
# name[index]=value
# or
# name=(value1 value2 …value1)

devices=”cpu”
devices[1]=”keyboard”
devices[2]=”mouse”
devices[3]=”monitor”

subjects=(“database” “image processing” “java” “Netwotk Security”)

echo “The Second element of Device array is ${devices[1]}”

#To display or access the values of an array
# ${name[*]}
# ${name[@]}
echo “The Values of devices array”
echo ${devices[*]}
echo “The Values of subjects array”
echo ${subjects[*]}

#Creating Constants or readonly variables
PI=3.14285
readonly PI
# You cant change the value of PI
echo “The Value of Constant PI is $PI”

#Unsetting the Variable
unset devices
unset var
unset subjects
echo $var

#Output of this program

# This is the Demo Program for Variables
# The Second element of Device array is keyboard
# The Values of devices array
# cpu keyboard mouse monitor
# The Values of subjects array
# database image processing java Netwotk Security
# The Value of Constant PI is 3.14285
#

For Creating Shell programs
# vi filename.sh

For Running Shell Programs
# sh filename.sh
or
# chmod 744 filename.sh
#./filename.sh