From: Gregory Seidman <gsslist+ruby@...>
Date: 2007-07-01T22:21:12+09:00
Subject: Re: awk regexp search

On Sun, Jul 01, 2007 at 10:13:16PM +0900, baptiste Augui? wrote:
> Hi,
> 
> The last bit of a bash program is still resisting me. Here is the  
> code I used before:
> 
> awk '/scattering efficiency/{print $4}' ../OUTPUTFILES/Output.dat
> 
> How would you do that in Ruby? I just need to locate this regexp in  
> the file, and get the following value in the same line. I've tried  
> something like,
> 
> output_file=IO.readlines('../OUTPUTFILES/Output.dat').to_s
> myarray = output_file.each_line(/scattering efficiency/){|elt| print  
> elt.to_s, '\t'}
> 
> but it clearly doesn't work.

First off, don't be too quick to abandon awk. I took a dozen lines of Ruby
someone wrote that did almost what I wanted and ported/replaced it with
three lines of sh/awk. For what awk can do, it is excellent.

To set up the equivalent of the awk code above, you want something like
this (note: untested):

ARGF.each { |line|
  case line
  when /scattering efficiency/
    puts line.split(/\s+/)[3] #note 3 instead of 4
  end
}

Note that this basic framework does not support awk's /regex1/,/regex2/
notation that captures lines between (and including) the lines matching
those regular expressions.

> Best regards,
> baptiste
--Greg