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Re: Bug#467376: coreutils: Wish there was a version of dd with multiple

From: Jim Meyering
Subject: Re: Bug#467376: coreutils: Wish there was a version of dd with multiple output files
Date: Mon, 25 Feb 2008 09:39:56 +0100

Russell Coker <address@hidden> wrote:
> Package: coreutils
> Version: 5.97-5.3
> Severity: wishlist
> When setting up test environments (chroots and Xen domains) I often want to
> duplicate one block device or large file to several others.
> If I am creating three copies I don't want to read the data three times and
> write it three times, I want to read it once and write it three times.

That does sound useful.

> dd if=source of=dest1 of=dest2 of=dest3 bs=102400k

You'd need to use something other than "of=", since
the above command has always simply ignored all but the last one.
I.e., it's equivalent to this:

    dd if=source of=dest3 bs=102400k

Hmm... but we *could* add an option to make it do what you suggest.

> The ideal would be something like the above.  But a separate utility as part
> of coreutils to perform the same task would be OK.
> Ideally such a program would use asynchronous IO or threads to allow all
> writes to be performed at the same time (when writing to a RAID array three
> writes theoretically can potentially be completed in the same amount of time
> as one write).

Would you like to write the patch? :-)
Or even just add it to the TODO list?

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