Ruby in Practice: Regular expressions

Helpful Ruby regular expression cheat sheet
http://www.tutorialspoint.com/ruby/ruby_regular_expressions.htm
Manipulating file contents with regular expressions in Ruby
http://snippets.dzone.com/posts/show/2595


I don't often need to work with regular expressions -- and when I do I usually use regex search and replace in Eclipse or Notepad++.  Today, however, I had a requirement that was harder to address with search and replace.  A great opportunity to try my new Ruby skills.
I needed to take something like this:

...
   <outer>
      <message-driven id="GreenPepper_sub_1" initialState="running" />
      <message-driven id="Habanero_sub_1" initialState="running" />  
      <message-driven id="Avacado_sub_1" initialState="running" />
...

and replace it with this:

...

   <outer>

      <message-driven id="GreenPepper_sub_1" initialState="running" />

      <message-driven id="GreenPepper_sub_2" initialState="running" />

      <message-driven id="GreenPepper_sub_3" initialState="running" />

      <message-driven id="Habanero_sub_1" initialState="running" />   

      <message-driven id="Habanero_sub_2" initialState="running" />   

      <message-driven id="Habanero_sub_3" initialState="running" />   

      <message-driven id="Avacado_sub_1" initialState="running" />

      <message-driven id="Avacado_sub_2" initialState="running" />

      <message-driven id="Avacado_sub_3" initialState="running" />

..

There were three other differently-formatted files which required a similar change -- in all several hundred lines making manual cut and paste an uninviting task (especially considering the number of typos I was likely to make with so many changes).  Basically, take a line with "_sub_1" and add a few duplicate lines afterward replacing "_sub_<n>"with "_sub_<n>" where <n> is 2 or 3.

As with most one-off utility scripts I didn't want to spend two hours doing one hour's worth of work, so I didn't super-optimize the script, but it worked great.  You can see that some of the files had lines with "channel 1" which required a similar change.  This one script worked great for all files:

# script to add extra lines to rib-*-adapters-resources.properties

#                          and rib-*-adapters.xml

# for multi-channel

def replace_in_file(filename="D://rib//file4.txt", match="tafr_1")

  File.open(filename, "r") {|f| lines = f.readlines

    lines.each {|line|

      puts line

      if line =~ /#{match}/

        replace line, match

      end

    }

  }

end

def replace(line, match)

  (2..3).each {|i|

    tempLine = line.to_s.gsub(match, match[0..match.index("_1")]+"#{i}")

    tempLine = tempLine.to_s.gsub("channel 1", "channel #{i}")

    puts tempLine

  }

end