From: Jonathan Dobbie <jdobbie@...>
Date: 2007-11-10T06:21:30+09:00
Subject: Re: How to edit a file without loading it all into memory

7stud -- wrote:
> Jonathan Dobbie wrote:
>> The lines are easy to
>> find with grep, and I'm able to create the new line easily enough, but
>> how can I do this without holding the entire file into memory?  The
>> files can be hundreds of megabytes.
>> 
> 
> File.foreach("data.txt") do |line|
>   #look for something in line
> end

Here is what I originally wrote, and what I just tried.  Am I missing 
something obvious?  The first one duplicates the lines, and the second 
one does nothing.  (doesn't save the changes)

  def change_texture_paths
    File.open(Dir.glob(ENV['HOME'] + "/*.ma").first, "r+") do |file|
      file.grep( /setAttr ".fileTextureName" -type "string"/ ) do |line|
        texture_file_path = line[52..-2]
        texture_file_name = texture_file_path.split("\/").last
        line = "        setAttr \".fileTextureName\" -type \"string\" 
\"" + ENV['HOME'] + "/include/" + texture_file_name + "\n"
        file.print line
      end
    end


    File.foreach(Dir.glob(ENV['HOME'] + "/*.ma").first, "r+") do |line|
      if (line =~ /setAttr ".fileTextureName" -type "string"/ )
        texture_file_path = line[52..-2]
        texture_file_name = texture_file_path.split("\/").last
        line = "        setAttr \".fileTextureName\" -type \"string\" 
\"" + ENV['HOME'] + "/include/" + texture_file_name + "\n"
        file.print line
      end
    end
 end
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