A Dropbox client for the raspberryPI

Overview

Raspybox is a minimalistic but powerful dropbox client written in python for the RaspberryPI.

How to use it

There are three forms that the program can be executed. The simplest is the graphical way. First you have to execute raspberryDropy.py and type login. Follow the instructions and when you finish press ctrl+D to exit. Now you can use it in any of the three forms.

Setting things up

You need to install the dropbox sdk for python (which can be found in dropbox developer page) and create your own app. Download all the files from the file directory of this project and place them in a directory. Create an app for the whole dropbox and copy paste the keys in raspberryDropy.py accordingly.

User Interfece

To execute the user interface simply type ./raspberryDropy_gui.py . The user interface should come up after a few seconds.
You can also use some shortcuts instead of the menu:
For upload press insert key.
For delete press delete key.
To refresh press F5
To navigate through your directories use the arrow keys and enter or double mouse click to either enter a directory or download a file.
There will be some messages in the console, don't worry about them. If the program crashes send the output as a bug report to the developer. This is because it is the initial version, so it might have some serious bugs.

Dropbox command line

You can also execute the raspberryDropy.py and use the dropbox from the command line. Type help to view the necessary commands.

Alternative command line

Because the RaspberryPI is very useful when using scripts and command line fire and forget programs such a functionality is supported. Instead of running ./raspberryDropy.py to access command line, you can supply a dropbox command as argument. Then the program will start-up execute the command, display the output and die. Be ware that the cache can't work on such situations. You can modify it to keep a cache on a file instead of the memory or use your own in your script.
This part however needs further development and consideration, so the command line can be used efficiently and fast enough (for example it makes no sense to run a command for changing directory, it will be of no use for this purpose)

Contribution

Currently the code is not very well commented, but it should not be very difficult to understand it, since it's a small program. However, a commenting will be done soon, I hope. If you want to contribute to this program, please send a request.

Download

Currently, the target groups are developers, testers and PI hobbyists, but anyone can have a go with it.
You can find everything here:   http://sourceforge.net/p/raspybox/wiki/Home/

Finding probabilities for RISK

During holidays we find ourselves playing board games. One of the best out there is RISK. During game-play, one might wonder what are the probabilities for each battle scenario. Moreover, if that someone is, well, a geek, he might write a program during game-play to support his army with a little of, em, technology.
So, do we know an equation to find those probabilities? No. Probably we'll find one with a little google search, but why not study it using a more programming method? We have the technology, we know a little bit of programming, so, let's take our chances.

1. import java.util.Arrays;
2. public class RiskProbability
3. {
4. private static int[] diceThrow(int n)
5. {
6. int[] dice = new int[n];
7. for (int i = 0; i < dice.length; i++)
8. dice[i] = (int)(Math.random()*6) + 1;
9. Arrays.sort(dice);
10. return dice;
11. }
12. public enum winner {ATTACKER, DEFENDER, TIE};
13. private static winner battle(int a, int d)
14. {
15. int[] attacker = diceThrow(a);
16. int[] defender = diceThrow(d);
17. int aSoldiersLost=0;
18. int dSoldiersLost=0; 
19. int j=defender.length - 1;
20. for (int i = attacker.length - 1; i >= 0 && j >= 0 ; i--)
21. {
22. if (attacker[i] > defender[j--])
23. dSoldiersLost++;
24. else
25. aSoldiersLost++;
26. }
27. if (aSoldiersLost > dSoldiersLost)
28. return winner.DEFENDER;
29. else if (dSoldiersLost > aSoldiersLost)
30. return winner.ATTACKER;
31. else
32. return winner.TIE;
33. } 
34. public static void main(String[] args)
35. {
36. int experimentSize = Integer.parseInt(args[0]);
37. int attWins = 0, defWins = 0, ties = 0;
38. int attStyle = Integer.parseInt(args[1]);
39. int defStyle = Integer.parseInt(args[2]);
40. for (int ex = 1; ex <= experimentSize; ex++)
41. {
42. winner w = battle(attStyle, defStyle);
43. switch (w)
44. {
45. case ATTACKER: attWins++; break;
46. case DEFENDER: defWins++; break;
47. case TIE: ties++; break;
48. default: break;
49. }//switch
50. }
51. System.out.println("Experiment is with " + attStyle + " attackers and " + defStyle + " 
52. defenders " + experimentSize + " times");
53. System.out.println((attWins/(double)experimentSize) + " attackers");
54. System.out.println((defWins/(double)experimentSize) + " defenders");
55. System.out.println((ties/(double)experimentSize) + " ties");
56. }//main
57. }

Let's explain the code a bit.
Lines 4-11 is the definition of a throw dice function. You specify the number of dice to throw, and a sorted array of the values of each die is returned. Watch out because the dice are sorted in ascending order.

Line 12 is an enumeration to be used for specifying the winner.
Line 13 is the definition of the battle function that takes two arguments, the number of dice the attacker will use and those of the defender as a second argument. Then the diceThrow is called and the battle begins on lines 20-26 until one runs out of dice.
Line 34 is the main method where the battle is initiated for 'experimentSize' number of times using the specified number of dice for each player.
To run this properly you have to pass 3 integer arguments, the experiment size (1000000 should be more than enough), the number of dice of the attacker and the number of dice of the defender. These are the results obtained by using the above program:

$ java RiskProbability 1000000 3 2
Experiment is with 3 attackers and 2 defenders 1000000 times
0.371734 attackers
0.291923 defenders
0.336343 ties

java RiskProbability 1000000 2 2
Experiment is with 2 attackers and 2 defenders 1000000 times
0.227412 attackers
0.448301 defenders
0.324287 ties

$ java RiskProbability 1000000 3 1
Experiment is with 3 attackers and 1 defenders 1000000 times
0.66038 attackers
0.33962 defenders
0.0 ties

$ java RiskProbability 1000000 2 1
Experiment is with 2 attackers and 1 defenders 1000000 times
0.578971 attackers
0.421029 defenders
0.0 ties

$ java RiskProbability 1000000 1 1
Experiment is with 1 attackers and 1 defenders 1000000 times
0.416221 attackers
0.583779 defenders
0.0 ties

$ java RiskProbability 1000000 1 2
Experiment is with 1 attackers and 2 defenders 1000000 times
0.25389 attackers
0.74611 defenders
0.0 ties

So, the next time you'll play RISK, you'll know.

 

Linux: The power of Open Source

Everyone that had a go with Linux, has an idea of what Open Source Software means. For those who don't, open source means that the code of the programming language that the software is written and in general the pre-compiled units of it are available to the public.
This gives a lot of advantages. Many programmers can contribute to the code or users that know a couple of things in programming can modify a piece of code and re-compile it to cover their needs and then maybe share it with others that have the same needs. That's how every open source community has been working so far.
We've all heard about it, but few of us have seen it. How do we modify the code? How do we find it? There are a lot of possibilities and options here. For example, most recent programs for Ubuntu are written in Python (e.g. Gwibber). In those programs it won't be difficult to find the code, since Python is not compiled but it's an interpreter based environment. In other words, you can see the code if you open the program with a text editor.

Let's see the real stuff now with an example. We came along the program "fortune" recently and tried to run fortune -f in Fedora, which displays the files that fortune looks at to generate a fortune cookie. We wanted to pass the output data through pipe but it didn't work:
fortune -f | grep humour
After a couple of failures, we assumed that the output was redirected to STDERR instead of STDOUT. But, this is unacceptable code practice. Why send data that are normal output to the error stream? So we downloaded the fortune source rpm package. Here is the process that followed:

• Find the repository of the fedora-mod.rpm, google is your friend.
• Find the source code which is in form fortune-mod.src.rpm
  Create a folder in your home directory (/home/username/) named rpmbuild and inside it a directory named SOURCES 
• Install developer tools and recode-devel: sudo yum install @development-tools recode-devel
• Extract the rpm in the /home/username/SOURCE/ directory.
• Modify the code, in that case we found fortune.c and changed in the function print_list() every fprintf(stderr... to fprintf(stdout... (yes it was that simple)
• To compile it and pack it run rpmbuild -ba fortune-mod.spec.

You can find the rpm now in the rpmbuild/RPMS directory from where you can install it but first run yum remove fortune-mod if you already have it install in your machine.


We've found the source from here

Android presentation

Download the android presentation (08/10/2012- Man-UP) from here.