From: Li Chen <chen_li3@...>
Date: 2007-07-31T05:46:18+09:00
Subject: Re: why writing the file is partial

Rick Denatale wrote:
> He needs to seek back to the beginning of the line before he writes:
> 
>         file.each_line do |line|
>                if pat.match(line)
>                      line.gsub!(pat,sub)  #replace the line in place
>                      file.seek(-line.length, IO::SEEK_CUR)
>                      file.print line    #write/update the file
>                end
>         end
>      end
> 
> But this will only work in the case where the replacement is the same
> length at the original, if you you're either going to leave stuff
> behind, or will overwrite the next line.  In either case you're more
> likely to end up with gibberish than something you like.

HI Rick,

Now I work on a small project with deals with process files and upgrade 
the them in place. Just as you point out the #seek only works if the 
replacement is the same as the original. And the replacement will get 
unpredictalbe results or fail if the length is different. I wonder if 
other methods are available for this situation in Ruby?

Thanks,

Li
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