From: Robert Klemme <shortcutter@...>
Date: 2008-11-07T02:38:44+09:00
Subject: Re: how to quickly find a string towards the end of a large io object

2008/11/6 bwv549 <jtprince@gmail.com>:
> I really appreciate all the comments.  They are very helpful.  I
> should have been more specific:
>
> In this case, I am dealing with a file that will usually be >= 100
> MB.  It may easily be up to 1GB or more.  The file is in binary form,
> but about 9/10ths of the way there is a small text file embedded into
> it.  I need to check a parameter in the file before processing the
> complete binary format (which I've decoded).  At this point I only
> expect to see files, but I was hoping to make it generic to any IO
> object.  I would settle on a solution for a file (rather than an IO
> object), but I would like it to be cross-platform and prefer the
> solution in ruby if it is fast enough (who wouldn't).
>
> Again, the basic layout of the file:
>
> ................................my_param = X........
>
> I need the value 'X' following the 'my_para = '

For simplicity reasons I'd start with this:

def get_param(file_name)
  size = File.size file_name
  File.open file_name do |io|
    io.seek(-(size * 0.1).to_i, IO::SEEK_END)
    io.read[%r{my_param\s*=\s*(\S+)}, 1]
  end
end

Kind regards

robert

-- 
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