xkcd explained

January 8, 2010
filed under genevainformation, rant
Tagged , , ,

I fully understand that the non-unix-non-technical person will not find xkcd funny at all.

Admin Mourning

That’s why I thought about explaining xkcd. And while I started to think about how I possibly could explain this comic I realized how deep down in Unix you need to be to fully grasp the funny part here. Oh my, we’re lost!

Well, let me try like this: On a Unix system, users “log on”, as they do in windows. Only that real computers don’t have a graphical user interface but are used on the command line. If you want that experience in Windows, start “cmd.exe”. You’ll start something like a shell, well, actually it *is* a shell: A text-based, line-oriented interface to the computer. You type a command, the computer does it. You type the next one, the computer does it. And so on.

A shell is a program. A program is always executed by a user and attached to his “session”. A session can time out, but to prevent so you can use a program called screen. Screen will detach your program execution from your session.

Now, if the user starts screen, then a shell and disconnects, screen will make sure that your session stays alive and the program is still executed.

Over the last few lines of text I have been desperately trying to come up with a sensible analogy..so let me try this: If you go shopping and take a shopping cart you will take it empty and leave it empty. The shopping cart is your session, the products inside the programs you run. The normal process is that you go in, take  a shopping cart. You fill it with products, take out products and so on. Latest when you go to the cashier, your shopping cart will be emptied completely. That’s your normal system log off – your session ends, all programs are terminated.

Screen is like a bag you put in your shopping cart. Once you have that bag in your cart, you can decide whether you want your stuff directly in the cart or in the bag which is in the cart. When you now need to leave the shop, you can do the following: Instead of either going to the cashier and pay or empty your shopping cart, you can leave the bag in the shop, go away, come back and pick it up again later.

All the complexity to leaving a bag full of groceries in a shop apply to screen as well – you can forget about it, the products can become stale or, if the shop closes down, someone will sweep out the bag you left behind (that’s a rule, bags can’t stay in the shop if it closes).

So the above comic refers to shopping bags left in the shop. The people who created them will never come back, but full of good memories, the shop owner will never close down because he knows that if he closes the shop, he will have to remove the bags. Instead he keeps the memory alive and passes by from time to time to look at the leftovers of human beings in his shop, represented by bags full of rotten grocery. Sort of.

xkcd – A webcomic of romance, sarcasm, math, and language – By Randall Munroe.

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