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Re: Is it possible to dd from a position in a file to the end?
From: |
Pádraig Brady |
Subject: |
Re: Is it possible to dd from a position in a file to the end? |
Date: |
Wed, 20 Feb 2019 00:06:33 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 |
On 19/02/19 11:46, Peng Yu wrote:
> Hi, I don't see a way to specify "END" in dd. I don't want to count
> the length a file in another command. Is there a way to let dd dump
> from a given location to the end? Thanks.
There is no way at present, without first determining the size
and seeking relative to that.
dd seek=$calculated_size oflag=seek_bytes ...
If you wanted to replace the end of a file in place,
and if atomicity isn't a concern (which it couldn't be if
the size was big enough), one might combine truncate like:
truncate -s -$size file
dd conv=notrunc oflag=oappend ...
If you just wanted to read the last portion of a file,
one could use tail (which also supports devices since v8.29) like:
tail -c$size ...
cheers,
Pádraig