From: Robert Klemme <shortcutter@...>
Date: 2006-11-25T04:51:49+09:00
Subject: Re: double-slashes in input causing trouble


Some more remarks:

On 23.11.2006 17:53, Hugh Sasse wrote:
> On Fri, 24 Nov 2006, Jeremy Wells wrote:
> 
>         [...]
>> The problem is that if the section contains "\\" which mine does in places,
>> ruby replaces these with a single "\" without my asking it to.
>>
>> Here is the basics of the program:
>> body = ""

Initializing body with an empty string is superfluous - nil is more 
efficient, but:

>> File.open(input, 'r') do |file|
>>    body = file.read
>> end

You could as well replace those lines with

body = File.read input

>> if body =~ /^section\sheader(.*)section\sfooter/mi

Dangerous to use .* which is greedy and will break if there are more 
sections in one file!

>>    original_section = $1
>>    new_section = bit_at_top + original_section
>>    new_body = body.sub(original_section, new_section)
>      new_body = body.sub(Regexp.new(Regexp.quote(original_section)),
>                                            new_section)

Now you do a replacement with sub which might replace some completely 
different piece of text (i.e. especially if the text of original_section 
appears outside a section or otherwise in multiple places.

>>    File.open(input,'w') do |file|
>>       file.write new_body
>>    end
>> end
> 
>         # Hugh
> 

So, combining these you get:

body = File.read input

if body.gsub!( %r{^(section\sheader)(.*?)(?=section\sfooter)}mi,
   '\\1your_head\\2')
   File.open(input, "w") {|io| io.write body}
end

Kind regards

	robert