[Uw-ruby] week 6 homework

[Ryan Davis]

to be mirrored to http://www.zenspider.com/~ryand/uw_ruby/ :

This week we'll be working on more "real world" applications of ruby.  
One of the strongholds of ruby is sysadmin work. Sysadmins work on  
fileservers, webservers, networks, and everything else that we need to  
keep things running. Most of the time, they're walking into an  
unfamiliar environment or trying to diagnose a problem that they don't  
have a handle on yet. So, to help them out, we're going to work on two  
utilities that will help them figure stuff out.

## Problem #1: power grep

Admins need to look at network information and file systems alike, so  
why not give them one tool to help? Power grep will search both files  
and sockets:

   pgrep -i error /var/log/system.log http://www.example.com/status.txt

That's right, I want to search for "error" on both the system.log and  
on a url in the same invocation!

   Minimum requirements:

	1) Must search files and http urls, as many as passed in.

	2) -i for case insensitive searches.

	3) -f for "fast grep" - no regular expression, just literal text.

	4) -q for quiet, just denote match via exit code

   Remember: each feature set must be fully tested. The only thing  
that shouldn't bother with tests is the single line at the bottom:

	PowerGrep.run(ARGV) if $0 == __FILE__

   How you design, break that up, and test/mock/stub is up to you.
   Use the mailing list for help.

## Problem #2: file statistics

Admins often have to deal with large and unfamiliar file systems under  
severe time constraints. If a disk is full, or acting weird, they need  
to be able to react quickly. Let's help them out. Design a program  
that will give them some useful information that might help them  
figure out what to do on short notice.

   Minimum requirements:

	1) Must walk a whole file tree and provide "useful" information.

	2) Must report the N biggest files names and sizes in readable fashion.

	3) Must report the N biggest "groups" of file types (by file  
extension).

	4) Must report the N oldest files names, dates, and sizes.

	5) N can be specified as a command-line argument (-n), defaulting to  
10.

   In order to test this, break it up in such a way that everything  
but the actual file system walker can be tested. Something like:

> class AdminUtil
>   def self.run dir = '.'
>     au = AdminUtil.new
>     data = au.gather_data dir
>     au.report data
>   end
>
>   def initialize
>     #
>   end
>
>   def report stats
>     # stats is a hash of path => [File::Stat] info
>   end
> end
>
> AdminUtil.run if __FILE__ == $0

Bonus points for those who mock out the file system walker itself so  
it can be tested as well.