GNU bug report logs - #18119
df --si misleading output units

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Kernc <kerncece <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: df --si misleading output units
Date: Sun, 27 Jul 2014 20:43:29 +0200

Hi,

By example,

$ df --human-readable /dev/sdb2
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdb2        82G   66G   12G  86% /home
$ df --si /dev/sdb2
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdb2        88G   71G   13G  86% /home

In both cases, the output unit presented is G(iB) whereas a
power-of-1000 unit (GB) was requested in the latter invocation.

Message #8 received at 18119 <at> debbugs.gnu.org (full text, mbox):

From: Bob Proulx <bob <at> proulx.com>
To: Kernc <kerncece <at> gmail.com>
Cc: 18119 <at> debbugs.gnu.org
Subject: Re: bug#18119: df --si misleading output units
Date: Sun, 3 Aug 2014 15:19:16 -0600

Kernc wrote:
> By example,
> 
> $ df --human-readable /dev/sdb2
> Filesystem      Size  Used Avail Use% Mounted on
> /dev/sdb2        82G   66G   12G  86% /home
> $ df --si /dev/sdb2
> Filesystem      Size  Used Avail Use% Mounted on
> /dev/sdb2        88G   71G   13G  86% /home
> 
> In both cases, the output unit presented is G(iB) whereas a
> power-of-1000 unit (GB) was requested in the latter invocation.

Saying "G" does not specify either GiB nor GB.  It specifies the
magnitude in the unit requested.  Saying that it specifies GiB in both
cases is incorrect.

If SI powers of ten units were requested then that is emitted.  If
human readable powers of two units were requested then that is
emitted.

Bob

Message #11 received at 18119 <at> debbugs.gnu.org (full text, mbox):

From: Kernc <kerncece <at> gmail.com>
To: Bob Proulx <bob <at> proulx.com>
Cc: 18119 <at> debbugs.gnu.org
Subject: Re: bug#18119: df --si misleading output units
Date: Mon, 4 Aug 2014 15:31:45 +0200

[Message part 1 (text/plain, inline)]

I understand. It does not specify the value in GiB, but the unit presented
- you say it's only magnitude, I'm calling it unit here¹ – is G, which
implies GiB, which makes it completely ambigous with regard to the output
unit of e.g. `--block-size=G` switch.

Please compare:

$ df --human-readable /dev/sdb2 | tail -1
/dev/sdb2        82G   67G   12G  86% /home
$ df --block-size=G /dev/sdb2 | tail -1
/dev/sdb2            82G   67G       12G  86% /home
$ df --si /dev/sdb2 | tail -1
/dev/sdb2        88G   71G   12G  86% /home
$ df --block-size=GB /dev/sdb2 | tail -1
/dev/sdb2            88GB  71GB      12GB  86% /home

Since `--block-size=GB` outputs the value in GB, and 'GB' is the unit
appended, why doesn't `--si` do the same (use SI-units to mark
"SI-magnitude" values)?

¹: Units are defined by order of magnitude prefix (e.g. G) and of base unit
(e.g. B). In our example, if the program only supplies the magnitude and
lets the common base unit be inferred, one gets 'GB' for `--si`. Which is
correct. But what other unit of can one thus construct when using `-h`
switch?

[Message part 2 (text/html, inline)]

Message #14 received at 18119 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Kernc <kerncece <at> gmail.com>, Bob Proulx <bob <at> proulx.com>
Cc: 18119 <at> debbugs.gnu.org
Subject: Re: bug#18119: df --si misleading output units
Date: Mon, 04 Aug 2014 07:07:43 -0700

Kernc wrote:
> Since `--block-size=GB` outputs the value in GB, and 'GB' is the unit
> appended, why doesn't `--si` do the same (use SI-units to mark
> "SI-magnitude" values)?

Because it's more concise that way, and because it's been that way for 
years.  No doubt it could have been done differently, but at this point ...

Message #17 received at 18119 <at> debbugs.gnu.org (full text, mbox):

From: Kernc <kerncece <at> gmail.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 18119 <at> debbugs.gnu.org, Bob Proulx <bob <at> proulx.com>
Subject: Re: bug#18119: df --si misleading output units
Date: Mon, 4 Aug 2014 18:49:43 +0200

[Message part 1 (text/plain, inline)]

The maturity of bugs is always a valid reason not to fix them. And "Unix"
is being phased out soon anyway.

[Message part 2 (text/html, inline)]

Message #20 received at 18119 <at> debbugs.gnu.org (full text, mbox):

From: Filipus Klutiero <chealer <at> gmail.com>
To: 18119 <at> debbugs.gnu.org, 18119-subscribe <at> debbugs.gnu.org
Subject: Confirmed
Date: Sat, 13 Sep 2014 14:13:12 -0400

I confirm. info says:

> With human-readable formats, output sizes are followed by a size
> letter such as ‘M’ for megabytes.  ‘BLOCK_SIZE=human-readable’ uses
> powers of 1024; ‘M’ stands for 1,048,576 bytes.  ‘BLOCK_SIZE=si’ is
> similar, but uses powers of 1000 and appends ‘B’; ‘MB’ stands for
> 1,000,000 bytes.

There is at least a documentation bug, but in my book a bug in the output. "82G" is not a size.

-- 
Filipus Klutiero
http://www.philippecloutier.com

Message #23 received at 18119 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: 18119 <at> debbugs.gnu.org
Subject: Re: bug#18119: df --si misleading output units
Date: Fri, 19 Oct 2018 21:52:50 -0600

tags 18119 wontfix
severity 18119 wishlist
close 18119
stop

(triaging old bugs)

On 04/08/14 08:07 AM, Paul Eggert wrote:
> Kernc wrote:
>> Since `--block-size=GB` outputs the value in GB, and 'GB' is the unit
>> appended, why doesn't `--si` do the same (use SI-units to mark
>> "SI-magnitude" values)?
> 
> Because it's more concise that way, and because it's been that way for 
> years.  No doubt it could have been done differently, but at this point ...

Note that in the meantime coreutils gained a new program: "numfmt".
This program performs unit conversions with much finer control,
including GiB and GB and others.

"numfmt --help" even includes the following examples:
---
$ df -B1 | numfmt --header --field 2-4 --to=si
---

Given the above, and with no further comments in 4 years, I am closing
this report.

-assaf

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