dash: details of redirection/duplication in manpage are reversed

dash: details of redirection/duplication in manpage are reversed

[Stéphane Aulery]

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forwarded 501566 dash@vger.kernel.org
stop
-------------------------------------------------------

Hello,

Here is a small patch reported by a user of Debian [1]. Could you please
integrate? Thank you for your help.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=501566

Regards,

-- 
Stéphane Aulery

[-- Attachment #2: dash.1.fix-redirection-docs.diff --]
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--- dash.1.old	2014-11-10 12:15:29.809398575 +0100
+++ dash.1.new	2014-11-10 12:17:03.401856125 +0100
@@ -402,11 +402,11 @@
 .It [n] Ns \*[Lt] file
 Redirect standard input (or n) from file.
 .It [n1] Ns \*[Lt]& Ns n2
-Duplicate standard input (or n1) from file descriptor n2.
+Duplicate standard input (or n1) to file descriptor n2.
 .It [n] Ns \*[Lt]&-
 Close standard input (or n).
 .It [n1] Ns \*[Gt]& Ns n2
-Duplicate standard output (or n1) to n2.
+Duplicate standard output (or n1) from n2.
 .It [n] Ns \*[Gt]&-
 Close standard output (or n).
 .It [n] Ns \*[Lt]\*[Gt] file

Re: dash: details of redirection/duplication in manpage are reversed

[Herbert Xu]

Stéphane Aulery <saulery@free.fr> wrote:
> 
> --IS0zKkzwUGydFO0o
> Content-Type: text/plain; charset=utf-8
> Content-Disposition: inline
> Content-Transfer-Encoding: 8bit
> 
> forwarded 501566 dash@vger.kernel.org
> stop
> -------------------------------------------------------
> 
> Hello,
> 
> Here is a small patch reported by a user of Debian [1]. Could you please
> integrate? Thank you for your help.
> 
> [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=501566
> 
> Regards,
> 
> -- 
> Stéphane Aulery
> 
> --IS0zKkzwUGydFO0o
> Content-Type: text/x-diff; charset=utf-8
> Content-Disposition: attachment; filename="dash.1.fix-redirection-docs.diff"
> 
> --- dash.1.old	2014-11-10 12:15:29.809398575 +0100
> +++ dash.1.new	2014-11-10 12:17:03.401856125 +0100
> @@ -402,11 +402,11 @@
> .It [n] Ns \*[Lt] file
> Redirect standard input (or n) from file.
> .It [n1] Ns \*[Lt]& Ns n2
> -Duplicate standard input (or n1) from file descriptor n2.
> +Duplicate standard input (or n1) to file descriptor n2.
> .It [n] Ns \*[Lt]&-
> Close standard input (or n).
> .It [n1] Ns \*[Gt]& Ns n2
> -Duplicate standard output (or n1) to n2.
> +Duplicate standard output (or n1) from n2.
> .It [n] Ns \*[Gt]&-
> Close standard output (or n).
> .It [n] Ns \*[Lt]\*[Gt] file

I'm sorry but this patch looks wrong and the text looks correct
to me as is.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: dash: details of redirection/duplication in manpage are reversed

[Stéphane Aulery]

Le lundi 10 novembre 2014 à 09:24:09, Herbert Xu a écrit :
> Stéphane Aulery <saulery@free.fr> wrote:
> > 
> > [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=501566
> > 
> 
> I'm sorry but this patch looks wrong and the text looks correct
> to me as is.

Ok. I passed the information but I'm not really able to judge its
pertinence. In this case I close this bug.

Thank you for your help.

-- 
Stéphane Aulery

Re: Bug#501566: dash: details of redirection/duplication in manpage are reversed

[Stephen Shirley]

Hi,

On 10 November 2014 14:49, Stéphane Aulery <saulery@free.fr> wrote:
> Le lundi 10 novembre 2014 à 09:24:09, Herbert Xu a écrit :
>> Stéphane Aulery <saulery@free.fr> wrote:
>> >
>> > [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=501566
>> >
>>
>> I'm sorry but this patch looks wrong and the text looks correct
>> to me as is.
>
> Ok. I passed the information but I'm not really able to judge its
> pertinence. In this case I close this bug.

So, i finally managed to figure out what the problem is. The wording
is ambiguous (or maybe just insufficiently clear).

"[n1]>&n2    Duplicate standard output (or n1) to n2."

How i read it (6 years ago :P) was that meant dup2(n1, n2), because
the only actual /duplication/ is of file descriptors. I've just
realised that the intended meaning is "redirect n1 to where n2 is
currently", i.e. dup2(n2, n1), as expected. Can i suggest a simple
fix:

"[n1]>&n2    Redirect standard output (or n1) to n2."

It doesn't cover the case where n2 is later changed, and how n1 does
not follow this, but it's the simplest fix i see.

Steve
-- 
"You are technically correct, the best kind of correct."
- Bureaucrat 1.0, Futurama

Re: Bug#501566: dash: details of redirection/duplication in manpage are reversed

[Stephane Chazelas]

2014-11-11 14:23:21 +0100, Stephen Shirley:
[...]
> "[n1]>&n2    Redirect standard output (or n1) to n2."
> 
> It doesn't cover the case where n2 is later changed, and how n1 does
> not follow this, but it's the simplest fix i see.
[...]

That's ambiguous.

Maybe:

[n1]>&n2    Redirect standard output (or fd n1) to the same "open
            file description" as on fd n2.

[n1]>&n2    Redirect standard output (or fd n1) to the same
            resource as open on fd n2.

[n1]>&n2    Copy fd n2 as stdout (or fd n1)

?

-- 
Stephane

Re: Bug#501566: dash: details of redirection/duplication in manpage are reversed

[Herbert Xu]

On Tue, Nov 11, 2014 at 02:23:21PM +0100, Stephen Shirley wrote:
>
> "[n1]>&n2    Redirect standard output (or n1) to n2."
> 
> It doesn't cover the case where n2 is later changed, and how n1 does
> not follow this, but it's the simplest fix i see.

Yes that sounds much better.  Please send a patch.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

dash: details of redirection/duplication in manpage are reversed

[Stéphane Aulery]

Hello,

Le mardi 11 novembre 2014 à 11:08:05, Herbert Xu a écrit :
> On Tue, Nov 11, 2014 at 02:23:21PM +0100, Stephen Shirley wrote:
> >
> > "[n1]>&n2    Redirect standard output (or n1) to n2."
> > 
> > It doesn't cover the case where n2 is later changed, and how n1 does
> > not follow this, but it's the simplest fix i see.
> 
> Yes that sounds much better.  Please send a patch.

Here is one. Stephen, the correction of the first line is abandoned?

[n1]<&n2    Duplicate standard input (or n1) from file descriptor n2.

Regards,

-- 
Stéphane Aulery

dash: details of redirection/duplication in manpage are reversed

[Stéphane Aulery]

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Hello,

Le mardi 11 novembre 2014 à 11:08:05, Herbert Xu a écrit :
> On Tue, Nov 11, 2014 at 02:23:21PM +0100, Stephen Shirley wrote:
> >
> > "[n1]>&n2    Redirect standard output (or n1) to n2."
> > 
> > It doesn't cover the case where n2 is later changed, and how n1 does
> > not follow this, but it's the simplest fix i see.
> 
> Yes that sounds much better.  Please send a patch.

Here is one. Stephen, the correction of the first line is abandoned?

[n1]<&n2    Duplicate standard input (or n1) from file descriptor n2.

Regards,

-- 
Stéphane Aulery

[-- Attachment #2: dash.1.fix-redirect-output.diff --]
[-- Type: text/x-diff, Size: 365 bytes --]

--- dash.1.old	2014-11-11 21:33:03.740785197 +0100
+++ dash.1.new	2014-11-11 21:41:02.747126940 +0100
@@ -406,7 +406,7 @@
 .It [n] Ns \*[Lt]&-
 Close standard input (or n).
 .It [n1] Ns \*[Gt]& Ns n2
-Duplicate standard output (or n1) to n2.
+Redirect standard output (or n1) to n2.
 .It [n] Ns \*[Gt]&-
 Close standard output (or n).
 .It [n] Ns \*[Lt]\*[Gt] file

Re: dash: details of redirection/duplication in manpage are reversed

[Herbert Xu]

On Tue, Nov 11, 2014 at 09:47:27PM +0100, Stéphane Aulery wrote:
> Hello,
> 
> Le mardi 11 novembre 2014 à 11:08:05, Herbert Xu a écrit :
> > On Tue, Nov 11, 2014 at 02:23:21PM +0100, Stephen Shirley wrote:
> > >
> > > "[n1]>&n2    Redirect standard output (or n1) to n2."
> > > 
> > > It doesn't cover the case where n2 is later changed, and how n1 does
> > > not follow this, but it's the simplest fix i see.
> > 
> > Yes that sounds much better.  Please send a patch.
> 
> Here is one. Stephen, the correction of the first line is abandoned?
> 
> [n1]<&n2    Duplicate standard input (or n1) from file descriptor n2.

Please incorporate the comments by Stephane Chazelas.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: Bug#501566: dash: details of redirection/duplication in manpage are reversed

[Herbert Xu]

Stephane Chazelas <stephane.chazelas@gmail.com> wrote:
> 2014-11-11 14:23:21 +0100, Stephen Shirley:
> [...]
>> "[n1]>&n2    Redirect standard output (or n1) to n2."
>> 
>> It doesn't cover the case where n2 is later changed, and how n1 does
>> not follow this, but it's the simplest fix i see.
> [...]
> 
> That's ambiguous.
> 
> Maybe:
> 
> [n1]>&n2    Redirect standard output (or fd n1) to the same "open
>            file description" as on fd n2.
> 
> [n1]>&n2    Redirect standard output (or fd n1) to the same
>            resource as open on fd n2.
> 
> [n1]>&n2    Copy fd n2 as stdout (or fd n1)
> 
> ?

Stephane, please keep the cc list in future list replies as
otherwise people may miss your messages since not everyone is
subscribed and even those subscribed may filter out messages
not addressed to them directly.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: dash: details of redirection/duplication in manpage are reversed

[Stéphane Aulery]

Hello,

Le mercredi 12 novembre 2014 à 10:12:04, Herbert Xu a écrit :
> On Tue, Nov 11, 2014 at 09:47:27PM +0100, Stéphane Aulery wrote:
> > Le mardi 11 novembre 2014 à 11:08:05, Herbert Xu a écrit :
> > > On Tue, Nov 11, 2014 at 02:23:21PM +0100, Stephen Shirley wrote:
> > > >
> > > > "[n1]>&n2    Redirect standard output (or n1) to n2."
> > > > 
> > > 
> > > Yes that sounds much better.  Please send a patch.
> > 
> > Here is one. Stephen, the correction of the first line is abandoned?
> 
> Please incorporate the comments by Stephane Chazelas.

I'm not subscribed to the list, I had missed the message of Stephane
Chazelas. What proposal do you want please?

[n1]>&n2    Redirect standard output (or fd n1) to the same "open
            file description" as on fd n2.

[n1]>&n2    Redirect standard output (or fd n1) to the same
            resource as open on fd n2.

[n1]>&n2    Copy fd n2 as stdout (or fd n1)

Thanks,

-- 
Stéphane Aulery

Re: Bug#501566: dash: details of redirection/duplication in manpage are reversed

[Stéphane Aulery]

Hello Stephen,

Le mardi 11 novembre 2014 à 02:23:21, Stephen Shirley a écrit :
> On 10 November 2014 14:49, Stéphane Aulery <saulery@free.fr> wrote:
> > Le lundi 10 novembre 2014 à 09:24:09, Herbert Xu a écrit :
> >> Stéphane Aulery <saulery@free.fr> wrote:
> >> >
> >> > [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=501566
> >>
> >> I'm sorry but this patch looks wrong and the text looks correct
> >> to me as is.
> >
> > Ok. I passed the information but I'm not really able to judge its
> > pertinence. In this case I close this bug.
> 
> So, i finally managed to figure out what the problem is. The wording
> is ambiguous (or maybe just insufficiently clear).
> 
> "[n1]>&n2    Duplicate standard output (or n1) to n2."


Herbert rejected both corrections. Your new proposal is better but
incomplete. Stéphane Chazelas tried to complete it. Moreover you have
not made a new proposal for the first correction.

As I am not dash user, I do not have a good knowledge of the matter. Can
you complete your answer / choice, please?

Thank you in advance for your help.


Original version:

1)  [n1]<&n2    Duplicate standard input (or n1) from file descriptor n2.

2)  [n1]>&n2    Duplicate standard output (or n1) to n2.


Version on Debian bug tracker and refused by H. Xu:

1)  [n1]<&n2    Duplicate standard input (or n1) to file descriptor n2.

2)  [n1]>&n2    Duplicate standard output (or n1) from n2.


Second version of the patch refused by H. Xu:

2)  [n1]>&n2    Redirect standard output (or n1) to n2.


Stéphane Chazelas proposals:

1a) [n1]>&n2    Redirect standard output (or fd n1) to the same "open
                file description" as on fd n2.

1b) [n1]>&n2    Redirect standard output (or fd n1) to
                the same resource as open on fd n2.

1c) [n1]>&n2    Copy fd n2 as stdout (or fd n1)


Regards,

-- 
Stéphane Aulery

Re: Bug#501566: dash: details of redirection/duplication in manpage are reversed

[Stéphane Aulery]

Hello Stephen and Herbert,

Stéphane Chazelas just made a complete proposal:


1) [n1]<&n2    Redirect standard input (or fd n1) from the same
               resource as open on fd n2.

2b) [n1]>&n2   Redirect standard output (or fd n1) to
               the same resource as open on fd n2.


What do you think about?

Regards,

-- 
Stéphane Aulery

Re: Bug#501566: dash: details of redirection/duplication in manpage are reversed

[Stéphane CHAZELAS]

2014-11-19 00:46:03 +0100, Stéphane Aulery:
> Hello Stephen and Herbert,
> 
> Stéphane Chazelas just made a complete proposal:
> 
> 
> 1) [n1]<&n2    Redirect standard input (or fd n1) from the same
>                resource as open on fd n2.
> 
> 2b) [n1]>&n2   Redirect standard output (or fd n1) to
>                the same resource as open on fd n2.
> 
> 
> What do you think about?
[...]

A final touch (add "currently").

 [n1]<&n2    Redirect standard input (or fd n1) from the same
             resource as currently open on fd n2.
 
 [n1]>&n2   Redirect standard output (or fd n1) to
            the same resource as currently open on fd n2.

-- 
Stephane

[MAN] Clarify two redirection mechanisms

[saulery]

From: Stéphane Aulery <saulery@free.fr>

Close Debian Bug #501566
---
 src/dash.1 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/dash.1 b/src/dash.1
index d782882..429657a 100644
--- a/src/dash.1
+++ b/src/dash.1
@@ -402,11 +402,13 @@ Append standard output (or n) to file.
 .It [n] Ns \*[Lt] file
 Redirect standard input (or n) from file.
 .It [n1] Ns \*[Lt]& Ns n2
-Duplicate standard input (or n1) from file descriptor n2.
+Redirect standard input (or fd n1) from the same resource as currently open on
+fd n2.
 .It [n] Ns \*[Lt]&-
 Close standard input (or n).
 .It [n1] Ns \*[Gt]& Ns n2
-Duplicate standard output (or n1) to n2.
+Redirect standard output (or fd n1) to the same resource as currently open on
+fd n2.
 .It [n] Ns \*[Gt]&-
 Close standard output (or n).
 .It [n] Ns \*[Lt]\*[Gt] file
-- 
2.1.3

Re: [MAN] Clarify two redirection mechanisms

[Herbert Xu]

saulery@free.fr wrote:
> From: Stéphane Aulery <saulery@free.fr>
> 
> Close Debian Bug #501566
> ---
> src/dash.1 | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/dash.1 b/src/dash.1
> index d782882..429657a 100644
> --- a/src/dash.1
> +++ b/src/dash.1
> @@ -402,11 +402,13 @@ Append standard output (or n) to file.
> .It [n] Ns \*[Lt] file
> Redirect standard input (or n) from file.
> .It [n1] Ns \*[Lt]& Ns n2
> -Duplicate standard input (or n1) from file descriptor n2.
> +Redirect standard input (or fd n1) from the same resource as currently open on
> +fd n2.

"Resource" is rather unwieldy, how about simply "file"?

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [MAN] Clarify two redirection mechanisms

[Stephane Chazelas]

2014-12-01 18:04:56 +0800, Herbert Xu:
[...]
> > --- a/src/dash.1
> > +++ b/src/dash.1
> > @@ -402,11 +402,13 @@ Append standard output (or n) to file.
> > .It [n] Ns \*[Lt] file
> > Redirect standard input (or n) from file.
> > .It [n1] Ns \*[Lt]& Ns n2
> > -Duplicate standard input (or n1) from file descriptor n2.
> > +Redirect standard input (or fd n1) from the same resource as currently open on
> > +fd n2.
> 
> "Resource" is rather unwieldy, how about simply "file"?
[...]

"file" could be misleading (as actually it's dup(2)ing a file
descriptor, so more like redirecting to same _open file
description_ (not the same as reopening the file like "n1>
/dev/fd/n2" does on Linux for instance) and "file" is understood
by many as "regular file" while here, it could be (and often is)
socket/pipe/devices...).

IMO, "resource" is vague enough so as not to give the wrong idea
and I like that wording because it conveys the intended
mechanism clearly ("redirect to same thing as"). But I agree
it's not ideal.

The "dupliciting fd x onto y" wording may be more correct, but
doesn't convey the redirection idea as clearly IMO.

-- 
Stephane