Monday, September 26, 2011

Qt4 and Ruby1.9.x

After a long period with no Qt4 support for Ruby 1.9, the qtbindings gem has stepped in to fill the void. This project packages the qtruby4-qtruby library from the korundum project, so the API is unchanged.

Installation is straightforward:

sudo gem install qtbindings

or for rvm users:

sudo rvm gem install qtbindings

Compatible with 1.8 as well.

Sunday, September 25, 2011

Determining installed version of Ubuntu

Neither uname nor motd are of much use in determining the version of Ubuntu installed on a third-party system, and searching for version details of key packages in dpkg is annoying.

Fortunately there is a utility called lsb_release that provides this information:

bash$ lsb_release -si
bash$ lsb_release -sr
bash$ lsb_release -sc

Complete all the way down to the silly nickname for each release.

Since this is an LSB utility, it's probably been in place for some time, silently waiting to provide more detail than uname. Seriously, would a mention in the SEE ALSO section of the uname manpage be *so* hard to add?

Wednesday, September 21, 2011

First impressions, redux

The R500 bit the dust over a year and a half ago. Most PC manufacturers were busy trying to crank out netbooks or a Macbook Air ripoff at the time, so there was no suitable replacement -- had to limp along with a Macbook Pro (ugh!) running Ubuntu until spring of this year.

What replaced the R500? A Thinkpad X1. It weighs twice as much, has no transreflective screen, and is a bit bulkier, but it is paradise after using that Macbook Pro for a year. Dedicated pageup/down keys! Home and End keys! A Delete key! THREE mouse buttons! A hardware kill switch for wifi and bluetooth! A freaken eSATA connector!

But why no grumpy install post detailing how to get Linux speaking to all the hardware? Because everything just works! Even the volume control buttons and the fingerprint reader. No joke. You can thank IBM's interest in Linux for that.

On top of the compatibility, it's a nice looking machine, powerful (64-bit debian runs great on a dual-core i5 with 8 GB of RAM), and tough -- GorillaGlass over the display, MILSPEC (assuming 810) shock and spill resistance (including a keyboard that drains *through* to the bottom of the laptop), the works.

The one caveat: it's best to use non-standard video drivers, as the standard debian/ubuntu Intel video driver became a bit crashy. Easily fixed, though, by adding the xorg-edgers PPA.

Sunday, September 18, 2011

.vimrc and UTF-8

Quick .vimrc config to display UTF-8 characters correctly:

" support UTF-8 automatically when not on console
if  has('gui_running') && has('multi_byte')
        set encoding=utf-8
        set fileencoding=utf-8
        set fileencodings=utf-8

Note that the gui_running requirement ensures that this will be used by gvim and by vim run from a terminal emulator (such as urxvt or mlterm), not by vim running from a virtual terminal or console.

Wednesday, September 7, 2011

Fixing strings(1)

The first step in any examination of a binary is to run strings(1) on it.

This usually results in output like the following:
bash$ strings /bin/ls
...which, needless to say, sucks.

The problem here is that a 'string' is any sequence of printable ASCII characters of a minimum length (usually 4).

The output of strings(1) can be made a bit more usable by discarding any string that does not contain a word in the system dictionary. 

An off-the cuff implementation of such a filter in Ruby would be:
#!/usr/bin/env ruby

ARGF.lines.each do |line|
  is_str = false
  line.gsub(/[^[:alnum:]]/, ' ').split.each do |word|
    next if word.length < 4
    is_str = true if (`grep -Fxc '#{word}' #{DICT}`.chomp.to_i > 0)
  puts line if is_str

This would then be passed the output of strings(1):
bash$ strings /bin/ls | ./strings.rb

This is super-slow for large executables, and will miss sprintf-style formatting strings that contain only control characters (e.g. "%p\n"), but for the general case it produces useful output.

Directions for improvement: load one or more dictionary files and perform lookups on them in Ruby. Search for english-like words by taking 4-letter prefixes and suffixes of each 'word' in the string and searching for dictionary words that start or end with that prefix/suffix. Provide early-exit from the inner field look when a match is found. Allow matches of sprintf formatting strings, URIs ('http://'), etc.