At times you may need to trace a ruby program's execution flow. Ruby's set_trace_func comes handy there.



When saved in a file called trace.rb and executed with $ ruby trace.rb, it outputs

2011-12-15 00:33:26 +0530 c-return trace.rb:3 set_trace_func Kernel
2011-12-15 00:33:26 +0530 line trace.rb:5
2011-12-15 00:33:26 +0530 c-call trace.rb:5 puts Kernel
2011-12-15 00:33:26 +0530 c-call trace.rb:5 puts IO
2011-12-15 00:33:26 +0530 c-call trace.rb:5 write IO
*** Hello World
2011-12-15 00:33:26 +0530 c-return trace.rb:5 write IO
2011-12-15 00:33:26 +0530 c-return trace.rb:5 puts IO
2011-12-15 00:33:26 +0530 c-return trace.rb:5 puts Kernel


My Android phone doesn't support DivX/XviD. To play videos on it. I need to convert them to MP4. Taking a note for myself if I need it later.

$ ffmpeg -i input_video.avi -f mp4 -vcodec libx264 -acodec libfaac -s 400x240 -ab 128k output_video.mp4

400x240 is the phone's screen resolution.

[Edit] Good parameters for high quality MPEG4 encoding:

-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300

3 (b) No Conflicting Uses. You may not use the Flixster API to develop (or instruct any third party to develop) a service that may reasonably be deemed to be directly competitive with Flixster’s products and services, unless you have been specifically permitted to do so in a separate written agreement with Flixster prior to the undertaking of the development and launch of such service.

Dear Rotten Tomatoes, what's the point of launching these APIs then?

I keep looking at stuff and try guessing its price in INR. Look around for calculator, check USD exchange rate and punch it in.

#!/usr/bin/env ruby
require 'rubygems'
require 'hpricot'
require 'open-uri'

FPAGE = 'http://finance.yahoo.com/q?s=USDINR=X'
XPATH = '/html/body/div/div[2]/div[4]/div[2]/div/div[2]/table/tr/td/big/b/span/'

amount = (ARGV.length == 1) ? ARGV[0].to_f : 1
amount = 1 if amount == 0

doc = Hpricot(URI.parse( FPAGE ).read)
element = doc.search( XPATH )
exchange_rate = element[0].to_s.to_f
puts "#{amount} USD = #{amount * exchange_rate} INR"

Now i no longer have to. Just running $ usdinr 197.21 gives the amount in INR. Save this file in /usr/bin/usdinr and give execute permissions.

[Update 2009-02-19: Updated the script with new XPath]
[Update 2010-12-08: Updated the script with new Yahoo finance page and XPath]

Two months back Mumbai's autorickshaw and taxi drivers went on a strike, demanding a steep increase in fares. While earlier the fare calculation was simple, after the new fare structure came in place, autorickshaw fare calculations became relatively complex.

I started http://rickfare.com on the day new fares came into effect after seeing the new complicated fare structure. Over time, friends pitched in for their cities and I added New Delhi, Ahmedabad, Pune and Navi Mumbai. Today Rickfare.com is accessed by thousands of commuters over a wide variety of mobile devices including iPhone, BlackBerry, Android, HTC and assorted Nokia handsets.

I'd like to thank Ashish Mehta, Atul Jha, Kartik Mistry and Kamaleshwar for helping out with auto fares of their cities

This post is a note for self. I always keep forgetting how to extract mp3 audio file from any video clip.

$ mencoder videofile.avi -of rawaudio -oac mp3lame -ovc copy -o audio-output.mp3

This is an awesome companion to the youtube video downloader - youtube-dl.py

So, you've recieved an invite from one of your several friends about mGinger service that lets you do blah blah and blah with sms and all that.

Talking of imitations, move over mGinger. here comes mGarlic.

During the recent server migration, I shifted svn services from http to https. Everything seemed to work fine, except for this error while creating branches.

frodo$ svn cp https://svn.xinh.org/svn/project/UberCool/trunk https://svn.xinh.org/svn/project/UberCool/branches/1.0
svn: Server sent unexpected return value (502 Bad Gateway) in response to COPY request for '/svn/project/!svn/bc/15/UberCool/trunk'
svn: Your commit message was left in a temporary file:
svn: 'svn-commit.tmp'
frodo$

Googling around a bit helped. I'm using HTTPS over Apache + dav_svn module. This issue can be fixed by enabling mod_headers module in Apache and adding the following line at the end of your VirtualHost.

RequestHeader edit Destination ^https http early