dd dies on SIGUSR1

Chris Rees utisoft at gmail.com
Tue Mar 22 20:02:18 UTC 2011

On 22 March 2011 18:16, David Schultz <das at freebsd.org> wrote:
> On Tue, Mar 22, 2011, Chris Rees wrote:
>> Since POSIX has SIGUSR[12] as undefined, I think it's a POLA violation
>> to have processes die when provided.
> Quite the contrary: The default behavior of SIGUSR1 on FreeBSD
> follows both POSIX and historical precedent, so changing it would
> be a violation of POLA.  Terminating the process is also the
> default on Linux.

However... I still think that because no-one in their right mind would
use SIGUSR[12] to terminate a program it's pointless for it to happen,
and can only cause annoyance.

People want to hold onto historical behaviour for no good reason, and
I feel that this is one of these occasions. There is no reason for it
apart from 'that's how it always has been [because no-one's
complained]'. I also disagree that it 'follows' POSIX, POLA *IMO* for
undefined behaviour is generally do nothing or report an error.

> Linux dd's interpretation of SIGUSR1 seems rather poorly
> considered, since as you note, utilities that don't handle it will
> simply die unexpectedly.  However, it certainly wouldn't hurt to
> patch FreeBSD's dd to handle SIGUSR1 the same way as SIGINFO.

Could the original patch in the PR be good enough then?

Thank you for the thoughts.

I'm sorry if I seem to be ranting, and I fully understand if my
proposal of changing the default of USR1 is rejected completely; I
just wanted to have a reasoned discussion.

David, if you think the original patch (which does what your last
paragraph says) is OK then feel free to take that as the Fix.



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