Supressing dd output

Dan Nelson dnelson at
Thu Dec 24 16:38:47 UTC 2009

In the last episode (Dec 24), Rolf G Nielsen said:
> Noel Jones wrote:
> > On Wed, Dec 23, 2009 at 10:19 PM, Rolf Nielsen wrote:
> >> I'm wondering if there's a way to supress the summary output from dd. 
> >> I'm working on a backup script, that encrypts the backups, and after
> >> encrypting overwrites the unencrypted file several times using dd. 
> >> I've tried to redirect the output with 2>&1 > /dev/null but it doesn't
> >> work.  Since I run the script from the daily_local variable in
> >> periodic.conf, and the script backs up 11 filsystems (ZFS) to separate
> >> files, the mail from periodic daily gets ridiculously long, and most of
> >> it being dd summaries.
> > 
> > Order matters.
> > 
> > dd ...   >/dev/null 2>&1
> Thanks Noel. I've never considered using that order before. Probably
> because first time I saw that construct and had it explained to me, it was
> ordered the way I had it, and I very rarely have any use for it, so I
> haven't really noticed that my way was wrong; I usually only redirect
> stdout if anything at all.  Anyway, now it works like a charm.  Thanks. 
> :)

2>/dev/null is really all you need, since dd only prints those info lines to
stderr (stdout usually being used as its stream output unless of= is used)

	Dan Nelson
	dnelson at

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