From: B Mills <bmill@...>
Date: 2007-02-01T02:26:49+09:00
Subject: parsing indented plain text

Hi.

I'm still kind of new to Ruby and scripting in general, and am trying to
select specific entries from the plain text output of the Apple System
Profiler which arranges data like this:

Network:

    Internal Modem:

      Type: PPP (PPPSerial)
      Hardware: Modem
      BSD Device Name: modem
      IPv4:
          Configuration Method: PPP
      IPv6:
          Configuration Method: Automatic
      Proxies:
          FTP Passive Mode: Yes

    Built-in Ethernet:

      Type: Ethernet
      Hardware: Ethernet
      BSD Device Name: en0
      IPv4 Addresses: 10.3.9.249

So on and so forth. (There is an XML output option, but it uses the
Apple plist format, which provides very little useful structure and a
much larger filesize). I want to find a way to parse this based on the
number of preceding white spaces at the beginning of the line (and then
by colon), so I can get a specific property from a Hash:

profile['Network:'][ 'Built-in Ethernet:']['IPv4 Addresses:']

I started out by using grep to create an array of of each level of
indentation, and nesting loops to select a range between two indexes of
that level:

key1 = file.grep(/^\w/)
key1.each do |k1|
  range1 = file.index(key1[key1.index(k1)]
  if k1 == key1.last
    range2 = range1
  else
    range2 = file.index(key1[key1.index(k1) + 1]
  end
  stub = file[range1...range2]
  key2 = stub.grep(^/\s\s\s\s\w/)
  key2.each do |k2|
  ....rinse and repeat...
    key3.each do |k3|

...and so on until I run out of indentation levels. I'm running into
problems where the loop stops at the last element and won't dig down
into anything below it. It also doesn't handle context, as there are
duplicate values in the file. I also tend to have the problem of making
things more complicated than they have to be, so I figure there is a
more elegant and Ruby-ish way to do this. Any suggestions?

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