.NET Butchering --> Code Butchering

This is probably long overdue, I am changing the title of the blog to reflect the fact that I've been posting less and less .NET related stuff. This is somehow related to the fact that I've been trying to get more experience on non-microsoft technologies (mainly working on my pet open-source project), trying to practice my credo of language agnosticism.

How to ssh into Amazon EC2 Linux instance (and copy stuff over)

This is easy enough on an absolute scale but can be a bit of a nightmare if you're windows-oriented (as I unfortunately am ... but I am trying to snap out of it).

Here's a list of steps:

• Create amazon instance with a new key pair
• Save your private key to a known location (it's a .pem file you'll download in the process)
• Make sure the folder with the private key has appropriate access otherwise it won't work (e.g. on mac: chmod -R 700 path/to/pvtk).
• In the EC2 dashboard go the the security group settings for the instance and open ssh port 22
• Connect: ssh -i path/to/key/myKey.pem root@my-ec2-public-ip.amazonaws.com 

An alternative to referencing your key on the ssh command is to add it via ssh-add (on mac).

Another thing you might wanna do is to copy stuff over to the EC2 instance - you can use the scp command:

scp test/winning.txt root@my-ec2-public-ip.amazonaws.com:temp-files/

Good luck!

T-SQL Convert string to datetime

This is the kind of stuff you don't wanna waste time on - and yet ...

DECLARE @test varchar(10)
SET @test = '12/31/2011'

DECLARE @test_date datetime
SET @test_date = CONVERT(datetime, @test, 101)

Heads or Tails? or: how to lose money at the roulette table

I've always wondered how many heads/tails you'd get in a row if you could just keep flipping coins forever. The other day I was bored so I put together a stupid matlab script to try it out (leaving out the "forever" bit).

It's obvious that in theory you could get a never ending series of heads or tails, but in practice that is infinitely unlikely to happen, so I just wanted to get a feel for a "reasonable" figure in terms of how many repetitions one should expect to experience if one actually started tossing coins (or betting money on red/black at the roulette) for a very long time.

Out of 100 million series of coin tosses (where a series is defined by an uninterrupted streak of heads or tails) the longest streak of identical outcomes was 26 (I wanted to try with a billion series but was taking too long).

That means that if you go to a casino to make money doubling bets on red/black (the so-called Martingale strategy) and you are particularly unlucky you might have to flush out 20*(2^25) = 671,088,630 $ (a single bet is usually at least 20 $) on your last bet to actually make a profit (plus all the money you spent to get there).

If you play smart though, and you wait for 5 reds/blacks in a row before you start betting against that, then you can get away with a last bet of only 20*(2^20) = 20,971,520 $ (that's 20 millions!).

Disable DIV with jQuery

Here's a lame trick I use to disable divs:

// this works on IE

// disable
$('#myDiv').attr('disabled', 'disabled');


// enable
$('#myDiv').attr('disabled', '');

Disabling the whole div doesn't seem to disable inputs in chrome and firefox though, so here's the alternative version drilling down to each single input elements:

// this works everywhere but looks weird in IE


// disable
$('#myDiv :input').attr('disabled', 'disabled'); 


// enable
$('#myDiv :input').attr('disabled', '');

Good hacking.