Floating-point Arithmetic Operation in Linux Shell

In the Bash shell, we can only perform integer arithmetic. If we want to perform arithmetic involving afloatingpoint or fractional values, then we will need to use various other utilities, such asawk,bc, and similar.

Let’s see an example of using the utility calledbc:

$ echo "scale=2; 15 / 2" | bc7.50

For using thebcutility, we need to configure a scale parameter. Scale is the number of significant digits to the right of the decimal point. We have told thebcutility to calculate15 / 2, and then display the result with the scale of2.

Another example is the following:

$ bc((83.12 + 32.13) * 37.3)4298.82

Many things can be done with thebcutility, such as all types of arithmetic operations including binary and unary operations; it has many defined mathematical functions. It has its own programming syntax.

You can get moreinformationabout thebcutility at:http://www.gnu.org/software/bc/.

Let’s look at usingawkfor floating-point arithmetic:

$ result=`awk -v a=3.1 -v b=5.2 'BEGIN{printf "%.2fn",a*b}'`
$ echo $result
16.12

You will be learning more aboutawkprogramming in the coming chapters. Therefore, we will not get into a detailed discussion ofawkin this session.

Let’s write a few more Shell scripts using thearithmeticprogramming skills we have learned so far.

Let’s write the Bash shell scriptarithmetic_08.shto determine whether an input integer is even or odd:

arithmetic_08.sh

#!/bin/bash 
echo "Please enter a value" 
read x 
y=`expr $x % 2` 
if test $y -eq 0 
then 
   echo "Entered number is even" 
else 
   echo "Entered number is odd" 
fi

Let’s test the program:

$ chmod +x arithmetic_08.sh
$ ./arithmetic_08.sh

Output:
"Enter a number"5
"Number is odd"
"Enter a number"
6
"Number is even"

Let’s write the script arithmetic_09.sh to find the length of an input string:

arithmetic_09.sh

#!/bin/bash 
echo "Please Enter the String:" 
read str 
len=`echo $str | wc -c` 
let len=len-1 
echo "length of string = $len"

Let’s test the script:

$ chmod +x arithmetic_09.sh
$ ./arithmetic_09.sh

This should produce the following output:

Output:

Enter String:Hello World
length of string = 11

Let’s write a script to calculate the area andcircumferenceof a rectangle and circle.

Write the shell scriptarithmetic_10.shas follows:

arithmetic_10.sh

#!/bin/bash 
echo "Please enter the length, width and radius" 
read length width radius 
areaRectangle=`expr $length * $width ` 
temp=`expr $length + $width ` 
perimeterRect=`expr 2 * $temp` 
areaCircle=`echo 3.14 * $radius * $radius | bc` 
circumferenceCircle=`echo 2 * 3.14 * $radius | bc` 
echo "Area of rectangle = $areaRectangle" 
echo "Perimeter of Rectangle = $perimeterRect." 
echo "Area of circle = $areaCircle." 
echo "Circumference of circle = $circumferenceCircle" 
echo

Let’s test the program:

$ chmod +x arithmetic_10.sh
$ ./arithmetic_10.sh

This should produce the following output:

Output:

Enter the length, width and radius5 10 5
Area of rectangle = 50
Perimeter of Rectangle = 30
Area of circle = 78.50
Circumference of circle = 31.40