From: Jeremy Bopp <jeremy@...>
Date: 2010-09-19T02:00:33+09:00
Subject: Re: search and replace

On 09/18/2010 11:14 AM, John Smith wrote:
> Both solutions almost work, only that I want the first instance to be 
> replaced.
> For example
> 
> 1 4
> 1 4
> 1 5
> 1 4
> 1 5
> 
> one four
> 1 4
> 1 5
> 1 4
> 1 5

Alright, so you only want a search/replace pair to apply to a single
line in the file to be processed.  After the search/replace pair has
been applied one time, it should be dropped from the list of pairs to
try so that it cannot be used on subsequent lines.  Try this:

changes = [
  ['string1', 'replacement1'],
  ['string2', 'replacement2'],
  ...
]

File.open('somefile') do |f|
  f.each do |line|
    line_changed = false
    changes.each do |change|
      if line.sub!(change[0], change[1]) then
        line_changed = true
        changes.delete(change)
        puts line
        break
      end
    end
    puts line unless line_changed
  end
end


-Jeremy