From: Erik Hollensbe <erik@...>
Date: 2008-08-26T07:28:33+09:00
Subject: Re: Open file, get first line, delete first line close file

Richard Schneeman wrote:
> i this is the code that i've already uploaded, and is currently 
> running...

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")

The point here is that almost all the work is done on the file 
descriptors instead of in memory. I don't know if ruby has a sendfile() 
implementation, but that would be the most ideal, as it'd instruct the 
OS to do the copy.
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