From: zdennis <zdennis@...>
Date: 2005-12-02T01:56:51+09:00
Subject: Re: What is the best way to edit a file to eliminate a line

Steve [RubyTalk] wrote:
> Mike Fletcher wrote:
> 
>> File.new( "stuff.txt" ) do | in |
>>   File.new( "newstuff.txt", "w" ) do |out|
>>     in.each { | line | out.print line unless line =~ /foo/ }
>>   end
>> end
> 
> That's remarkably similar to my current rough-n-ready approach  - the 
> one I consider inelegant...(N.B. the example above doesn't address the 
> problem of atomically replacing stuff.txt with newstuff.txt.)  I was 
> thinking that something like this would be preferable:
> 
> FileModify.open 'stuff.txt' { |mfile| mfile.delete(/foo/) }
> 
> Of course, I've just invented FileModify off the top of my head, and I 
> imagine it being 'transactional' - i.e. any exception arising in the 
> block would prevent any change to stuff.txt.  I'd prefer not to go 
> around re-inventing the wheel if FileModify (or something similar) 
> already exists.  I don't need it to be desperately scalable or quick - 
> on the other hand, reliability _is_ a key concern and I'd prefer to use 
> the neatest possible syntax.
> 

I have done some things like:

def write filename, data
   File.open( filename, 'w' ){ |file| file.write data }
end

begin
   data = IO.read( 'stuff.txt' )
   write 'stuff.txt', data.gsub( /^foo(\n|$)/, '' )
rescue
   write 'stuff.txt.orig', data
end


Zach