Subject: Re: dd and pipe question
To: None <current-users@NetBSD.ORG>
From: Christoph Badura <firstname.lastname@example.org>
Date: 04/14/1996 02:00:00
Travis Hassloch writes:
>gzip -dc foo.tar.gz | dd ibs=10240 obs=10240 conv=sync of=/dev/tape
You do NOT want conv=sync. It pads every *input* record to ibs. So
for every short read on the input, you get pad bytes added to make up
According to Chris Torek dd behaves as follows:
dd if=x of=y
is the same as:
dd if=x of=y ibs=512 obs=512
which means: open files x and y, then loop doing read(fd_x) with a
byte count of 512, take whatever you got, copy it into an output
buffer for file y, and each time that buffer reaches 512 bytes, do a
single write(fd_y) with 512 bytes.
On the other hand:
dd if=x of=y bs=512
means something completely different: open files x and y, then loop
doing read(fd_x) with a byte count of 512, take what you got, and do a
single write(fd_y) with that count.
So you want something like:
gzip -dc foo.tar.gz | dd obs=/dev/tape ibs=10k obs=10k
 The qoute is from an article posted to comp.unix.question on
4/3/1991 which I would have sworn I have saved somewhere but can only
find it as article 20.16 in "UNIX Power Tools".
Christoph Badura email@example.com
You don't need to quote my .signature. Everyone has seen it by now.
Besides, it doesn't add anything to the current thread.