[Toybox] dd man page

[Alain Toussaint]

In the feature request department, I would love a wipefs command who
does similar to how I use dd. current wipefs from e2fsprogs leave out
some artifact when asked to wipe disk signatures...

Al

2017-07-13 23:41 GMT-04:00 Alain Toussaint <atoussaint1976 at gmail.com>:
> Use case here:
>
> dd if=/dev/zero of=/dev/sd[a,b,c,d,etc...] bs=64MB (could go higher)
> conv=fsync status=progress
>
> The important bit for me is the status=progress or whatever you come
> up as a design to figure out disk throughput.
>
> It's the only use I have for dd.
>
> Al
>
> 2017-07-13 22:50 GMT-04:00 Rob Landley <rob at landley.net>:
>> On 07/12/2017 03:22 AM, Rob Landley wrote:
>>> Next up, a similarly close reading of the man page...
>>
>> Using ubuntu 14.04 as reference:
>>
>> Still dropping conv=ascii,ebcdic,ibm because that was already obsolete
>> 30 years ago.
>>
>> I can see adding conv=excl,nocreat (sure, you got notrunc already)
>>
>> Adding conv=fsync but not conv=fdatasync (If this breaks somebody's
>> script I can add it but is "sync data but not metadata" a hair we want
>> to split?)
>>
>> Let's see... iflag and oflag= are kind of silly. There's already
>> conv=excl,nocreat,excl,notrunc so why is append not there too? Why can
>> you have iflag=append? "direct" is micromanaging nonsense (it was
>> introduced for oracle's database code, we have sync if we want to be
>> sure it hit disk). And "directory" is just nonsensical on Linux.
>> (Apparently bsd can read binary directory info, but there's no _use_ for
>> it?)
>>
>> https://lists.gnu.org/archive/html/coreutils/2014-08/msg00032.html
>>
>> Sigh. But somebody did dig up a use case for nonblock:
>>
>> https://stackoverflow.com/questions/32057396/how-to-flush-named-pipefifo-in-non-blocking-mode-in-busybox-shell-script
>>
>> But busybox git still doesn't implement it so there can't be that big of
>> a demand? Hmmm...
>>
>> Alright, these _might_ make sense:
>>
>>   iflag=noctty,noatime,nonblock,nofollow
>>   oflag=append,noctty,noatime,nonblock,
>>
>> These are silly:
>>
>>   ?flag=direct,directory,dsync,fullblock,nocache
>>
>> (If you want to drop caches for some sort of benchmark you can
>> echo 3 > /proc/sys/vm/drop_caches)
>>
>> What on earth is count_bytes? answer: how dd should have worked in the
>> first place? Oh this is just a terribly designed command all around.
>> conv=bytes makes sense, having separate count-bytes, seek_bytes,and
>> skip_bytes and having them care whether you iflags= or oflags= them is
>> NONSENSE.
>>
>> This business with sending a signal to get status? If you want dd to
>> output periodic progress reports (or a progress bar), DO THAT.
>> status=bar or status=count would have been the obvious things to do.
>>
>> Ok, looking at the iflag/oflag things: noctty, noatime, nofollow, and
>> append don't make sense to specify for input/output. If you want it for
>> one you presumably want it for both. The only one that really needs to
>> distinguish input from output is "nonblock" (although not for the one
>> use case I could find, since /dev/null should never block...). And if we
>> needed to distinguish within conv it could just have done
>> conv=inonblock,ononblock.
>>
>> Sigh. Nobody's requested any of this stuff yet, it's not in posix, and
>> even busybox hasn't bothered to implement it so far...
>>
>> Right, question: should I
>>
>> A) copy the existing insanity
>>
>> B) just do:
>>
>>   conv=append,noctty,inonblock,ononblock,nofollow,bytes
>>   status=bar,count
>>
>> C) ignore it all and wait for people to complain about its absence?
>>
>> Does anybody have strong opinions on this? I'm leaning towards door #2
>> myself. Posix has had 15 years to catch up on this, and declined.
>>
>> Rob
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