From: Alex DeCaria <alex.decaria@...>
Date: 2009-02-23T11:59:22+09:00
Subject: Re: FileUtils.mv behaving not as documented

Rob Biedenharn wrote:
> On Feb 22, 2009, at 8:06 PM, Alex DeCaria wrote:
> 
>> The documentation for FileUtils.mv(src, dest) says that if src and  
>> dest
>> are on different disk partitions then it is supposed to act as a copy
>> instead.  But when I use it to copy a file from the "C:" drive to a
>> flash drive or mp3 player using another drive letter such as "E:" it
>> moves it and doesn't copy it as advertised.  Is this a bug, or is the
>> documentation incorrect?  I am using Ruby 186-26 on Windows.
>>
>> -Alex
> 
> 
> I think that the difference the documentation is attempting to point
> out is that a mv on a single partition just changes names and pointers
> in directory entries so it makes no difference the size of the file.
> On different partitions, the size of the file will matter because the
> effect is a copy followed by an unlink of the original file.
> 
> If you want to copy, call FileUtils.cp
> If you want to move, continue to call FileUtils.mv
> 
> -Rob
> 
> Rob Biedenharn    http://agileconsultingllc.com
> Rob@AgileConsultingLLC.com

Thanks.  Can you explain another curious bit of behavior I've noticed? 
I found that if I use the FileUtil.cp(src, dest) to copy a large file 
from say the C: to the E: drive, it takes much longer than if I first 
use FileUtil.cp(src, tmp) to copy the file to a temporary directory on 
the C: drive and then use FileUtil.mv(tmp, dest) to move the file from 
the temporary directory to the E: drive.  This has the same result as 
just doing FileUtil.cp(src, dest), but takes much less time.  If I'm 
doing this on a lot of files the time saving is significant, but I don't 
understand why.

In other words, if I do

FileUtil.cp("C:/somefile", "C:/Temp/somefile")
FileUtil.mv("C:/Temp/somefile", "E:/")

it is faster than if I do

FileUtil.cp("C:/somefile", "E:/")

-Alex
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