Lunduke
News • Science & Tech
The Fork Bomb: What it is, how it works, and where it originated
The idea started in 1969... and it's been causing computers to crash ever since.
December 03, 2023
post photo preview
:(){ :|:& };:

That simple line has been crashing systems in the Linux world for years — It is known as the (infamous) “BASH Fork Bomb”.

When run in a GNU/BASH shell, this BASH variant of the Fork Bomb will bring your average Linux system to its knees, lickety-split. A mere handful of characters that can cause a computer to cry “Uncle.”

But what, exactly, is a “Fork Bomb”? How do they work? And where on this green Earth of ours were they first created?

Come with me on a journey into the history, design, and usage of one of the most dastardly ideas in all of computing… of The Fork Bomb!

What is a Fork Bomb?

The idea of a Fork Bomb is simple: Create a piece of code that does one thing and one thing only: replicate running instances of itself. And do so as quickly as possible.

Here, a visual will help drive the idea home.

In this case each Bunny Rabbit represents one instance of the Fork Bomb. Each bunny makes two new bunnies. Quickly. Multiplying like, well, rabbits.

Each of those adorable little bunny rabbits may not take up much RAM… or much CPU time… but imagine 20 of them. Or 1000. Or, like, a bazillion?! That Fork Bomb will continue making running copies of itself just as long as the system allows it to (by continuing to have available memory or not fully crash).

With how quickly each Fork Bomb replicates itself… and the number of copies growing exponentially… you can see how they can become a problem in a hurry. Often causing a system to lock up quicker than you can say, “Maybe I shouldn't have pressed Enter.”

A real-world example… and how it works

Let’s take a look at that BASH version of the Fork Bomb again (as that is one of the most popular and famous examples).

(If you don’t know how BASH scripting works, no worries. I’ll break it down… make it nice and easy.)

:(){ :|:& };:

Ok. So how does this, ridiculous looking, collection of semi-random seeming characters, actually work?

Let’s break that apart into multiple lines to make it all easier to read.

: ( ) {

   : | : &

} ; :

This… is a BASH script function.

But there’s something… weird about it. Note the many usages of “:”? In this case “:” is being used as a function name.

“Why is using “:” as a function name weird,” you ask?

Because, on most UNIX-y systems, it is not allowed to use a character in a function name other than letters and numbers (and underscores). But the GNU version of BASH — which is commonly used on oh-so-many Linux systems — allows : and so many other characters to be used.

Why does GNU allow a “:”? Who knows. GNU be crazy.

Regardless…

Let’s replace the “:” in that BASH script with “rabbit”. That will, in addition to making it run on more UNIX systems, make this a bit easier to read.

rabbit() {
rabbit | rabbit &
}; rabbit

There. So much better. Here we go. Line by line.

Line 1: rabbit() {

That first line does something simple. It defines a function named “rabbit”. That’s it and that’s all.

Line 2: rabbit | rabbit &

Line 2 is the insidious part.

It calls the function named “rabbit”, and sends the output of that function to the function named “rabbit.”

But, here’s the thing, there really isn’t any output of the “rabbit” function. So this is really just a fancy way of calling the “rabbit” function twice… at the same time.

Yeah. The “rabbit” function calls itself, from within itself, then calls itself again.

Oh, and that “&” at the end? That's the BASH way of telling “rabbit” to run in the background.

The net result? Every “rabbit”, makes two new “rabbit”s.

Line 3: }; rabbit

That last nine simply ends the “rabbit” function… and then calls itself.

Note: I highly recommend not running this code on your system unless you do so in a virtual machine. Without taking the proper precautions… this will bring your system to its knees.

Every variation of a Fork Bomb operates in a roughly similar fashion. A small piece of code that creates copies of itself… repeatedly. Thus eternally replicating itself until the system runs out of resources.

The first Fork Bomb

The very first known usage of a “Fork Bomb” was way back in 1969 at the University of Washington.

There, a Burroughs B5500 computer had been installed three years earlier. A big computer that provided the first time-sharing system on the University of Washington campus (through a series of dial-up modems running at 110 baud). This was also the first computer at the University of Washington to provide disk storage for user files. Pretty cool.

A Burroughs B-5500. Not the one at the U of W, though. Classy looking machine, right?

On that big, beautiful Burroughs B-5500, someone reportedly wrote a small bit of code that would make two copies of itself — over and over again — until the memory of the machine was full and the entire system would crash.

That intrepid programmer named that tiny little program, appropriately: “RABBITS”

Fun historical tidbit: RABBITS for the Burroughs B-5500 was not, technically the first computer virus. That distinction appears to go to the 1971 “Creeper Virus”. While RABBITS predated Creeper by a good two years… RABBITS doesn’t really act like a virus. It requires a user to explicitly run it in order to cause its own mischeif.

The 1974 “Wabbit”

A similar piece of code was written on an IBM System/360, a few years later, in 1974. Clearly inspired by “RABBITS”, this new code was called “Wabbit” and was, as Elmer Fudd might say, quite “wascally”.

The IBM System/360 Model 22 control panel. That thing was awesome looking.

Legend has it that the individual who created “Wabbit” ran the program on the System/360 at work… causing the entire system to crash. The man, again according to legend, lost his job.

Fun bit-o-trivia: As years went on any program that would self-replicate when ran by the user… but wasn’t actually a virus… would become known as a "wabbit.” in honor of this particular event.

Some other variations on the Fork Bomb

There have been Fork Bomb type bits of code written in just about every language you can imagine. At the beginning we covered how to write a Fork Bomb in BASH. But, because this sort of mayhem is simply too much fun, below you will find code to create similar bits of functionality in several other programming languages.

Enjoy.

Just… you know… try not to get yourself fired.

Fork Bomb in C:

int main(void) {
for (;;) {
    fork();
}
}
Fork Bomb in Python:

#!/usr/bin/env python

    import os
    while True: os.fork()

Fork Bomb in Ruby:

#!/usr/bin/env ruby
loop { fork { bomb } }
community logo
Join the Lunduke Community
To read more articles like this, sign up and join my community today
6
What else you may like…
Videos
Podcasts
Posts
Articles
How Much of Linux is Antifa?

"GNOME is Antifa," says GNOME. "See you in prison I guess," says Elementary OS founder. Antifa is everywhere in Open Source.

More from The Lunduke Journal:
https://lunduke.com/

00:14:35
September 17, 2025
Internet Archive Reaches Secret Settlement with Universal Music

Internet Archive Founder, Brewster Kahle, was the final hold-out in reaching a settlement. Which is being kept confidential.

More from The Lunduke Journal:
https://lunduke.com/

00:10:54
September 16, 2025
CTO of Microsoft Azure: "USA is Fascist Regime"

Microsoft employees chanting "Go away, Jews!" Then Microsoft employees praising the murder of Charlie Kirk. Now the Microsoft Chief Technical Officer of Azure attacks the USA & Trump.

More from The Lunduke Journal:
https://lunduke.com/

00:09:50
November 22, 2023
The futility of Ad-Blockers

Ads are filling the entirety of the Web -- websites, podcasts, YouTube videos, etc. -- at an increasing rate. Prices for those ad placements are plummeting. Consumers are desperate to use ad-blockers to make the web palatable. Google (and others) are desperate to break and block ad-blockers. All of which results in... more ads and lower pay for creators.

It's a fascinatingly annoying cycle. And there's only one viable way out of it.

Looking for the Podcast RSS feed or other links? Check here:
https://lunduke.locals.com/post/4619051/lunduke-journal-link-central-tm

Give the gift of The Lunduke Journal:
https://lunduke.locals.com/post/4898317/give-the-gift-of-the-lunduke-journal

The futility of Ad-Blockers
November 21, 2023
openSUSE says "No Lunduke allowed!"

Those in power with openSUSE make it clear they will not allow me anywhere near anything related to the openSUSE project. Ever. For any reason.

Well, that settles that, then! Guess I won't be contributing to openSUSE! 🤣

Looking for the Podcast RSS feed or other links?
https://lunduke.locals.com/post/4619051/lunduke-journal-link-central-tm

Give the gift of The Lunduke Journal:
https://lunduke.locals.com/post/4898317/give-the-gift-of-the-lunduke-journal

openSUSE says "No Lunduke allowed!"
September 13, 2023
"Andreas Kling creator of Serenity OS & Ladybird Web Browser" - Lunduke’s Big Tech Show - September 13th, 2023 - Ep 044

This episode is free for all to enjoy and share.

Be sure to subscribe here at Lunduke.Locals.com to get all shows & articles (including interviews with other amazing nerds).

"Andreas Kling creator of Serenity OS & Ladybird Web Browser" - Lunduke’s Big Tech Show - September 13th, 2023 - Ep 044

The Lunduke Journal is going live at 1pm Eastern (10am Pacific, 5pm UTC) today -- on X, Rumble, Locals, & YouTube.

Might be live a few minutes earlier than that. Got a lot of stuff to cover.

post photo preview
September 17, 2025

You all, I think, will be very proud of me. All of my computers in the house, other than my desktop are now running Omarchy or Open Mandriva Linux.

Microsoft is so disgusting right now that I just can't not be using Linux.

I mean I am probably one of the most hardcore Windows developers on here. I still think a lot of my points are valid, but Microsoft is just so ethically bad that I can't support them willingly. I have to use Windows at work and development focuses on it in some cases.

BUT, I have already released 3 Linux based applications of my own, and that is something I NEVER thought I would do.

It is a crazy world.

https://github.com/2disbetter/

DHH backing Omarchy is the kind of support I was hoping would come to a desktop Linux distro. That it is Arch and uses Hyprland just makes me smile. I of course support xlibre, but I just really like Hyprland.

Anyway, figured this crowd would find all of this as ironic as I do. Hope you all are having a rad day!

Anyone have any experience running any of the BSDs (preferably OpneBSD or GhostBSD) on real hardware? I've got a Lenovo Yoga 7i that is a couple years old heading my way from a family member who was going to recycle it (the hinge broke and he bought a new computer) and a few other candidates for trying my hand at an authentic BSD for daily driving. Just not sure how much of a headache I'm going to have getting things to work with the devices I have handy.

Final Reminder: Lifetime Price Increase in 24 hours

This is just a super quick reminder (so no body misses out):

This Friday (September 19th), the price of a new Lifetime Subscription to The Lunduke Journal will be increasing from $200 to $300.

Which means: If you want to pick up a new Lifetime Subscription for the lower price, simply grab one (via Locals, Substack, or Bitcoin) by Thursday night (Sep 18th). That’s roughly 24 hours from the moment I am writing these words.

Obviously, once you have a Lifetime Subscription you’re set. You know. For life.

I wanted to give all of you some notice so you could grab one at the lower rate.

Also worth noting: The Lunduke Journal has phased out sales and discount promotions. The current price of a subscription is the best price.

This will be the final reminder before the change goes into effect.

-Lunduke

Read full Article
September 15, 2025
post photo preview
Lunduke Livestream: Tue, Sep 16 at 1pm Eastern

The Lunduke Journal regular live-streaming is back! The next show is Tuesday, September 16th (tomorrow) at 1pm Eastern (10am Pacific, 5pm UTC).

You can catch the live video, for free, on X, Rumble, YouTube, & Locals.

We’ve got a lot of Tech News to cover — and who knows what stories will pop up between now and then!

Time permitting, we’ll also be doing a little Nerdy Q & A. So, if you’ve got something you’d like to ask, join us in one of the chat rooms!

Also, quick reminder that the price of new Lifetime Subscription is going up this Friday. If you want one at the lower price, now’s your moment. We’ve also added some new perks for subscribers worth checking out.

See you nerd tomorrow!

-Lunduke

Read full Article
September 14, 2025
New Lunduke Journal Sub Perks, Lifetime Price Increase Next Week

A quick update: There are some new perks for Lunduke Journal subscribers, and an upcoming price increase for new Lifetime Subscriptions (if you want one of those at the lower price, you have a couple days).

All the details below.

Lifetime Subscription Price Increase

This coming Friday (September 19th), the price of a new Lifetime Subscription to The Lunduke Journal will be increasing from $200 to $300. I wanted to give all of you a few days notice so you could grab one at the lower rate.

If you want to pick up a Lifetime Subscription for the lower price, simply grab one (via Locals, Substack, or Bitcoin) by Thursday night (Sep 18th).

The prices for new Yearly and Monthly subscriptions will remain the same. No changes.

Reminder: The Lunduke Journal has phased out sales and discount promotions. The current price of a subscription is the best price.

New Perks for Lunduke Journal Subscribers

I am working on adding a few new perks for Lunduke Journal subscribers — a way of saying “Thank You” for making this work possible (while still keeping all of the articles and shows free for the world).

Here are the perks as of today.

Perks for all Subscribers (Monthly, Yearly, and Lifetime):

Note: The eBooks & Games are currently only available on Locals & Substack (due to platform features). Those perks will also become available to subscribers on X, YouTube, & Patreon next week. Stay tuned for access details.

Additional (Optional) Perks only for Lifetime Subscribers:

  • The Lunduke Journal will follow your account on X.

  • Your name (real, or internet handle) listed in a special thanks slide at the end of new Lunduke Journal videos.

Both of these perks are 100% optional.

If you are a Lifetime Subscriber, and would like to take advantage of either (or both), simply email “bryan at lunduke.com” with the subject line “Lifetime Perk” (that part is important, I get so many emails this will help me see yours) and include a link to your X profile and/or the way you want your name to appear at the end of videos.

One of the nice parts of having Lunduke Journal follow your X account… is it will make it far easier (and more likely) for me to see your comments.

Thank You

I am working to expand all of the regular perks (books, etc.) to subscribers across all platforms (which was a little tricky, considering the differences in each platform, but I managed to figure out how to do it) — while adding a few new ones as well.

Nothing crazy, just a way of saying “Thank You”.

Seriously.

From the bottom of my heart, thank you for your support. The Lunduke Journal is only possible thanks to each and every one of you.

-Lunduke

Read full Article
See More
Available on mobile and TV devices
google store google store app store app store
google store google store app tv store app tv store amazon store amazon store roku store roku store
Powered by Locals