From: Daniel Bush <dlb.id.au@...>
Date: 2008-08-27T08:54:37+09:00
Subject: Re: Open file, get first line, delete first line close file

Erik Hollensbe wrote:
> Richard Schneeman wrote:
> If the file is exceptionally large, you can save a lot of memory (and 
> processing time, likely), by doing something like this:
> 
> File.open("my_file") do |f|
>     f.readline
>     File.open("my_file.tmp", 'w') do |f2|
>         f2 << f.read
>     end
> end
> 
> FileUtils.mv("my_file.tmp", "my_file")
> 

Just on the "f2 << f.read" part, isn't this still reading the rest of
the file into ruby?
I was thinking more of reading stuff into a fixed buffer and then 
writing it.
ie
    while buf=f.read(32000)  # bytes
      f2.write buf   # or f2 << buf
    end
which will result in a bazillion more calls to IO#read and IO#write on a 
large file but doesn't read the whole thing into memory.  I'm not 
recommending this or anything - just wanted to clarify.


Daniel
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