How to calculate pi using a bash script

 

Introduction

By following our step-by-step guide, you’ll learn how to calculate pi using a Bash script while gaining a thorough understanding of the underlying code. We’ll review each line of the Bash script in detail, providing you with a clearer overview of how the script functions.

The Breakdown

Here is an example Bash script that calculates pi and redirects the result to a file:

#!/bin/bash

# Set the number of decimal places to calculate
decimal_places=10

# Calculate pi using the bc command
pi=$(echo "scale=$decimal_places; 4*a(1)" | bc -l)

# Redirect the result to a file
echo $pi > pi_result.txt

Step 1: Set variables

In this script, we first set the number of decimal places to calculate by assigning a value to the decimal_places variable. In this example, we set it to 10, but you can change this value to suit your needs.

Step 2: Calculate pi

Next, we calculate pi using the bc command. The echo command sends the calculation command to bc, which performs the calculation using the a() function to compute the value of pi. The scale variable sets the number of decimal places to output.

Step 3: Redirect the result

Finally, we redirect the output of the echo command, which contains the value of pi, to a file called pi_result.txt. You can name the output file whatever you like.

Note: If you plan to use our example, you’ll need to add the execute flag using the chmod +x command as shown below. Additionally, we’ve named our script calc_pi.sh.

Step 4: Run the script

Now it’s time to execute the script and review the results. Run the following command to make the calc_pi.sh script executable:

$ sudo chmod +x calc_pi.sh

As the root user, you can now execute the script with the following command:

# ./calc_pi.sh

If the script runs successfully, you should see the pi_result.txt file when you list the contents of your present working directory (pwd) :

# ls -l
total 8
-rwxr-xr-x. 1 root root 225 Mar 13 00:06 calc_pi.sh
-rw-r--r--. 1 root root  13 Mar 13 00:06 pi_result.txt

Cat the pi_result.txt file to view its contents:

# cat pi_result.txt
3.1415926532