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Count magical bunnies with LibreOffice Calc Jim Hall Wed, 01/25/2023 - 03:00

I love working with spreadsheets, and my favorite spreadsheet application is LibreOffice Calc. A spreadsheet is a grid of cells where each column is represented by letters and rows are numbered. You can perform all kinds of calculations using a spreadsheet. If you can perform a calculation based on other values, you can do that in a spreadsheet.

Here I illustrate how to use the LibreOffice Calc spreadsheet to perform a particular calculation called the Fibonacci Sequence. Fibonacci Sequence numbers pop up everywhere in mathematics and the sciences and are often used to model a simple population growth.

The magic bunny

Imagine a baby bunny who has moved into a new forest home. The forest is empty of all other bunnies; the bunny is alone. But this is a magic bunny — it is born pregnant, and all its children will also be born pregnant. Rabbits breed quickly, but especially so for this breed of magic bunny, which produces a new generation every year.

Let's call the year before the bunny arrived "year zero" or "iteration zero," when you had zero bunnies. A year later, you are at "year one" or "iteration one," with our first bunny.

The population of our magic bunny grows in this way: A baby bunny grows into an adult bunny after one year. An adult bunny will remain into the next generation but will produce another baby bunny. In other words, the rules for counting the bunny population are:

• baby bunny (b) → adult bunny (A)

• adult bunny (A) → adult bunny (A) plus a baby bunny (b)

Over time, the bunny population grows like this:

Iteration Population Count 0 - 0 1 b 1 2 A 1 3 Ab 2 4 AbA 3

As you can see, the bunny population grows very quickly. The forest will quickly be filled with magic bunnies.

Counting bunnies in a spreadsheet

How many bunnies will there be after five, ten, or 20 years? Looking at each iteration, the number of bunnies in any year is the sum of the previous two years. Fibonacci described this growth using this definition:

Fib(n) = Fib(n-1) + Fib(n-2) and: Fib(0) = 0 Fib(1) = 1

You can calculate this using LibreOffice Calc! Here's how.

Start with an empty spreadsheet and enter the first two iterations: 0 and 1. Label these with a column header called "n." To enter this into LibreOffice Calc, type "n" into cell A1, the value 0 in cell A2, and 1 in cell A3:

Image by:

(Jim Hall, CC BY-SA 4.0)

Enter the first two iterations of the magic bunny. In year zero, there were zero bunnies. In year one, there was one bunny. You can write that mathematically as Fib(0) = 0 and Fib(1) = 1. You can label this with a column header called "Fib(n)." Enter this into LibreOffice Calc by typing "Fib(n)" into cell B1, the number 0 in cell B2, and 1 in cell B3:

Image by:

(Jim Hall, CC BY-SA 4.0)

To calculate the bunny population in the next iteration, use a spreadsheet formula to calculate Fib(n) for year two. Since the count in any year is the sum of the counts of the previous two years, you can enter into cell B4 the spreadsheet formula =B3+B2. This is the sum of B3 and B2 using addition. LibreOffice Calc will perform the calculation and enter the final result into cell B4:

Image by:

(Jim Hall, CC BY-SA 4.0)

More great content Free online course: RHEL technical overview Learn advanced Linux commands Download cheat sheets Find an open source alternative Explore open source resources Use AutoFill to calculate future generations

Having entered the first few "n" and "Fib(n)" values, and the calculation for the next iteration, you can let LibreOffice Calc do the rest of the calculations. Notice that when you click on each cell in the spreadsheet, the cell outline has a small box in the lower-right corner. You can grab this box with your mouse and "stretch" the box to fill other cells in the spreadsheet.

When you stretch a cell to fill other cells, LibreOffice Calc uses a feature called "AutoFill" to enter values into the new cells. If you stretch a cell with a single value, AutoFill will iterate the number by one until it reaches the end of the series. For example, you can stretch cell A3 to fill other cells below it, which will fill the range with 2, 3, 4, and so on:

Image by:

(Jim Hall, CC BY-SA 4.0)

If you stretch a cell that has a calculation in it, LibreOffice Calc will try to extend the calculation for you. For example, if you stretch your calculation in B4 into cell B5, the new B5 will contain the formula =B4+B3. In other words, AutoFill translates the calculation. Each successive Fib(n) calculation will be the sum of the two cells above it:

Image by:

(Jim Hall, CC BY-SA 4.0)

You can continue to stretch the cells down, and AutoFill will continue the calculations:

Image by:

(Jim Hall, CC BY-SA 4.0)

So you learn that after 20 iterations, you will have 6,765 magic bunnies. That's a lot of bunnies! Over 6,000 bunnies in 20 years represent a very fast population growth, but it demonstrates how quickly the Fibonacci Sequence can add up to a forest full of magic bunnies. The calculation is relatively simple using LibreOffice Calc.

Follow along with this LibreOffice Calc tutorial to perform the Fibonacci Sequence calculation.

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Flickr, by Anssi Koskinen CC BY 2.0

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Why sysadmins should license their code for open source dboth Wed, 01/25/2023 - 03:00

As a Linux system administrator, I write a fair amount of code.

Does that surprise you? Well, I strive to be the "lazy" sysadmin, and I do this, in part, by reducing the number of repetitive tasks I need to do by automating them. Most of my automation started as little command-line programs. I store those in executable scripts for re-use at any time on any Linux host for which I have responsibility.

The problem with sharing unlicensed Code

I also like to share my code. I think that, if my code has helped me to resolve a problem, it can also help other sysadmins resolve the same or similar problems. This is, after all, the essence of open source — the sharing of code. While code sharing is a good thing, legal issues can prevent perfectly good code from being used as intended by the developer.

The primary problem is that many companies have legal departments that require them to keep copies of licenses. This makes it easy to understand their rights and obligations. Software without a license attached to it in any way becomes a legal liability. This is because there is no basis upon which to determine whether the code can be used legally or not. This can prevent perfectly good code from being used by many companies and individuals.

Why I license my code

One of the best ways I know to give back to the open source community that provides everyone with incredible programs like the GNU Utilities, the Linux kernel, LibreOffice, WordPress, and thousands more, is to make programs and scripts open source using an appropriate license.

Just because you write a program, believe in open source, and agree that programs should be open source code, does not make it open source. As a sysadmin, I do write a lot of code, but how many of you ever consider licensing your own code?

You have to make the choice to explicitly state that your code is open source, and decide which license you want it to be distributed under. Without this critical step, the code you create is functionally proprietary. This means the community cannot safely take advantage of your work.

You should include the GPLv2 (or your other preferred) license header statement as a command-line option that prints the license header to the terminal. When distributing code, I also recommend that you include a text copy of the entire license along with the code (it's a requirement of some licenses.)

A few years ago, I read an interesting article, The source code is the license that helps to explain the reasoning behind this.

I find it very interesting that in all of the books I have read, and all of the classes I have attended, not once did any of them tell me to include a license for the code I wrote in my tasks as a sysadmin. All of these sources completely ignored the fact that sysadmins write code too. Even in the conference sessions on licensing I've attended, the focus was on application code, kernel code, and even GNU-type utilities. None of the presentations so much as hinted that you should consider licensing it in any way.

Perhaps you've had a different experience, but this has been mine. At the very least, this frustrates me — at the most it angers me. You devalue your code when you neglect to license it. Many sysadmins don't even think about licensing, but it's important if you want your code to be available to the entire community. This is neither about credit or money. This is about ensuring that your code is, now and always, available to others in the best sense of "free and open source."

Eric Raymond, author of the 2003 book, The Art of Unix Programming writes that in the early days of computer programming and especially in the early life of Unix, sharing code was a way of life. In the beginning, this was simply reusing existing code. With the advent of Linux and open source licensing, this became much easier. It meets the needs of system administrators to be able to legally share and reuse open source code.

Raymond states, "Software developers want their code to be transparent. Furthermore they don't want to lose their toolkits and their expertise when they change jobs. They get tired of being victims, fed up with being frustrated by blunt tools and intellectual-property fences and having to repeatedly reinvent the wheel.” This statement also applies to sysadmins — who are also, in fact, software developers.

How I license my code

I mentioned adding an option to print the GPL (or other) license header as a command line option. The code below is a procedure that does so:

############################################# # Print the GPL license header # ############################################# gpl() { echo echo "############################################################" echo "# Copyright (C) 2023 David Both #" echo "# http://www.both.org #" echo "# #" echo "# This program is free software; you can redistribute it #" echo "# and/or modify it under the terms of the #" echo "# GNU General Public License as published by the #" echo "# Free Software Foundation; either version 2 of the #" echo "# License, or (at your option) any later version. #" echo "# #" echo "# This program is distributed in the hope that it will be #" echo "# useful, but WITHOUT ANY WARRANTY; without even the #" echo "# implied warranty of MERCHANTABILITY or FITNESS FOR A #" echo "# PARTICULAR PURPOSE. See the GNU General Public License #" echo "# for more details. #" echo "# #" echo "# You should have received a copy of the GNU General #" echo "# Public License along with this program; if not, write #" echo "# to the Free Software Foundation, Inc., 59 Temple Place, #" echo "# Ste 330, Boston, MA 02111-1307 USA #" echo "############################################################" echo } # End of gpl() end

That's the license, included as a function. You can add an option to the code. I like to place the new case sections in alphabetical order to make them a bit easier to find when performing maintenance. This is the GPL, so I chose g as the short option:

######################################### # Process the input options # ######################################### # Get the options while getopts ":ghc" option; do case $option in c) # Check option Check=1;; g) # display the GPL header gpl exit;; h) # Help function Help exit;; \?) # incorrect option echo "Error: Invalid option." exit;; esac done end

More for sysadmins Enable Sysadmin blog The Automated Enterprise: A guide to managing IT with automation eBook: Ansible automation for Sysadmins Tales from the field: A system administrator's guide to IT automation eBook: A guide to Kubernetes for SREs and sysadmins Latest sysadmin articles

These two bits of code are all that's needed to add a legitimate and enforceable license to your program.

Final thoughts

I always license all of my code. I recently presented a session on Bash at OLF (Open Libre Free, which used to be known as Ohio Linux Fest). Instead of using LibreOffice Impress for my presentation, I used a Bash program for the entire thing. After all, it is a presentation about Bash so why not make it a Bash program.

I did include my license code in that Bash program. That way everyone who encounters a copy of my program knows that it's properly licensed under GPLv3, and that they can use and modify it under the terms of that license. My code is the license.

One of the best ways I know to give back to the open source community that provides everyone with incredible programs is to make programs and scripts open source using an appropriate license.

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