It's the __birthday__ of your friend, and you want to give him a gift. It's a hard mission, because _he simply have everything you can imagine_...

Why not give to him something __special__ and __original__?  

For example, you could give to him a __collection of great musics__, __photos/videos/slideshow__ of your __best moments__ ,a __private key__ of a __wallet__ with __money__ you just created for him  or __any file__ you want.

You may asking for yourself: _What's the deal?_

I've been thinking about __easter eggs__ with a __toy inside__. But not a real __easter egg__. A __virtual easter egg__. 

I mean files inside of a file like a __.zip__ does.

 But what I'll teach here is not how to "zip" files.

 _It's about hacking a file __(in a good cause)___.

In this tutorial I will teach you how to deal with __cat__. 

![espeto.jpg](https://steemitimages.com/DQme38iTXLRQzmvywRKY57EgxWYQaLzKkzwHwGc4DaveqSx/espeto.jpg)

__No!__ _Not this cat_, but a __Linux command__. _By the way, this is my friend, __mr. Espeto___.

According to __Linux man__ , cat do the following:

_"Concatenate files and print on the standard output"_

But he will use this in a different way. We will use to __write bytes of a file in the end of another one__.

## What you will need:

* _Linux_ 
* _Pendrive_
* _Creativity_

https://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Tux.svg/280px-Tux.svg.png
<sup><sub>_lewing@isc.tamu.edu Larry Ewing and The GIMP [Attribution or CC0], via Wikimedia Commons_</sub></sup>

# Let's go then:

1. Create a folder(directory) inside your home folder. We can name it "stuff" for example. 
2. Open a terminal and __cd__ (change directory) to this directory you just created.
  ``` cd /home/username/stuff/ ```
3. Copy all the files you want to give to your friend inside this directory.
4. Select all your files and create a zip file. You can use the right mouse button for this. 
5. Open __Libre Office Writter__ and create a __pdf__. (This _pdf_ will be the container of the zip. The pdf is the easter egg and the zip the toy.)
6. Let's paste bytes of zip into the end of pdf file. (Don't forget to backup before doing this)
```cat files.zip  >> happy_birthday.pdf```
7. Now the __files.zip__ and the __pdf__ are one single large __pdf__.
8. Open the __pdf__ to see if this works. (Don't try edit this pdf, because you can mess the already messed file. : -) )
9. Let's test the extraction of the __files.zip__ from the __pdf__. The first thing you need to know is the size in bytes of __files.zip__ 
```du -b files.zip```
10. Use this bytes size information (NUMBER) you got with _du -b files.zip_  in the following command
```tail -c NUMBER files.zip > new_files.zip```
11. The __new_files.zip__ is created. Open it and test it.

## Video
<sub>_* Watch this video in fullscreen mode_</sub>
https://youtu.be/r98zGRTT7yc
```https://youtu.be/r98zGRTT7yc```


# Important
_Don't forget to put the instructions in the pdf about how to catch a cat by the tail command! 😊_
http://meowgifs.com/wp-content/uploads/2013/03/bag-with-atail.gif
<sup><sub>_[Image Source](http://meowgifs.com/498)_</sub></sup>




## FAQ

* __Can I use these commands in another operating system?__
_Sure! You can use it in __Windows__ using the __Mingw__ or __Mac__, the same command but the parameters may vary. I suggest you to use __Linux__ in a __Virtual Machine__ or boot it __liveCD__(you don't need to install)._
* __Is it dangerous to open a file like this?__ 
_No. Since the Adobe Reader and other softwares avoid execution of binary data, this will result in nothing._



# SUGGESTIONS

* You can give a high capacity pendrive with this file inside.
https://upload.wikimedia.org/wikipedia/commons/e/e5/Pendrive_Shape_of_key.JPG
<sup><sub>_By Ranjithsiji (Own work) [<a href="http://www.gnu.org/copyleft/fdl.html">GFDL</a> or <a href="http://creativecommons.org/licenses/by-sa/3.0">CC BY-SA 3.0</a>], <a href="https://commons.wikimedia.org/wiki/File%3APendrive_Shape_of_key.JPG">via Wikimedia Commons</a>_</sub></sup>
* You can upload this to any serve that support the file format you are using and share the link. Ex.: Google Docs, Dropbox, etc...
https://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Dropbox_Logo_01.svg/800px-Dropbox_Logo_01.svg.png
<sup><sub>_[Image Souce](https://commons.wikimedia.org/wiki/File:Dropbox_Logo_01.svg)_</sub></sup>
* You can make a __pps slideshow__ instead of __pdf__, why not?
https://upload.wikimedia.org/wikipedia/commons/e/e5/Movie_projector%2C_men_Fortepan_9711.jpg
<sup><sub>_FOTO:FORTEPAN / MHSZ [<a href="http://creativecommons.org/licenses/by-sa/3.0">CC BY-SA 3.0</a>], <a href="https://commons.wikimedia.org/wiki/File%3AMovie_projector%2C_men_Fortepan_9711.jpg">undefined</a>_</sub></sup>
* You can make a game "search for the clues".
https://upload.wikimedia.org/wikipedia/commons/e/e8/Magnifying_glass_2911.JPG
<sup><sub>_By Penarc (Own work) [<a href="http://www.gnu.org/copyleft/fdl.html">GFDL</a> or <a href="http://creativecommons.org/licenses/by-sa/3.0">CC BY-SA 3.0</a>], <a href="https://commons.wikimedia.org/wiki/File%3AMagnifying_glass_2911.JPG">via Wikimedia Commons</a>_</sub></sup>
* You can make a Geek box with pendrive and candies.
https://s-media-cache-ak0.pinimg.com/736x/af/90/cb/af90cb90a6dee6fa6c441a29ef72ced5--zombie-survival-kits-zombies-survival.jpg
<sup><sub>_[Image Source](https://www.pinterest.com/blondiegirl8187/zombie-survival-kits/)_</sub></sup>
 
* You can make a good use of a 3D printer and make a weird case for a pendrive or mini cd
  https://upload.wikimedia.org/wikipedia/commons/9/98/3D_Printed_Ancient_Egyptian_Figurine_1.png
<sup><sub>_Por Bradina [<a href="http://creativecommons.org/publicdomain/zero/1.0/deed.en">CC0</a>], <a href="https://commons.wikimedia.org/wiki/File%3A3D_Printed_Ancient_Egyptian_Figurine_1.png">undefined</a>_</sub></sup>
* You can make a program in basic language and save it into a rom to run in ancient computers with z-80(zilog) based architecture, that is possible with the use of a... Eh... Please forget this one.
https://upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Optical_Illusion.svg/800px-Optical_Illusion.svg.png
<sup><sub>_© Nevit Dilmen [<a href="http://creativecommons.org/licenses/by-sa/3.0">CC BY-SA 3.0</a> undefined <a href="http://www.gnu.org/copyleft/fdl.html">GFDL</a>], <a href="https://commons.wikimedia.org/wiki/File%3AOptical_Illusion.svg">undefined</a>_</sub></sup>  
<center>
## That's it! Thank you for reading!
https://media.giphy.com/media/bBptDWRDPOUcU/giphy.gif
<sup><sub>_[Image Source - Giphy](https://giphy.com/gifs/doctor-who-kitty-karen-gillan-bBptDWRDPOUcU/)_</sub></sup>  
</center>