Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

[Michael Albinus]

p.stephani2@gmail.com (Philipp Stephani) writes:

Hi,

[sorry that I chime in such late; I didn't follow the discussion in Bug#35328]

> +@cindex standard error process
> +If @var{stderr} is a buffer, Emacs will create a pipe process, the
> +@dfn{standard error process}.  This process will have the default
> +filter (@pxref{Filter Functions}), sentinel (@pxref{Sentinels}), and
> +coding systems (@pxref{Default Coding Systems}).  On the other hand,
> +it will use @var{query-flag} as its query-on-exit flag (@pxref{Query
> +Before Exit}).  It will be associated with the @var{stderr} buffer
> +(@pxref{Process Buffers}) and send its output (which is the standard
> +error of the main process) there.

FTR, the implementation in Tramp is different from what is described
here. And honestly, I even don't know, how to implement these two
processes for the remote case.

The current implementation in Tramp redirects stderr to a temporary
file, if it is separate from stdout. This temprary file is associated
with the :stderr buffer, and it runs auto-revert-mode. Maybe not very
elegant, but working so far.

I don't know whether we shall document this different behavior, or
whether we shall find an implementation in Tramp for what is
described. For the latter, I would need help, as said. Or at least ideas.

Best regards, Michael.

Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Date: Mon, 22 Apr 2019 22:59:01 +0200
> Cc: Philipp Stephani <phst@google.com>
> 
> > +@cindex standard error process
> > +If @var{stderr} is a buffer, Emacs will create a pipe process, the
> > +@dfn{standard error process}.  This process will have the default
> > +filter (@pxref{Filter Functions}), sentinel (@pxref{Sentinels}), and
> > +coding systems (@pxref{Default Coding Systems}).  On the other hand,
> > +it will use @var{query-flag} as its query-on-exit flag (@pxref{Query
> > +Before Exit}).  It will be associated with the @var{stderr} buffer
> > +(@pxref{Process Buffers}) and send its output (which is the standard
> > +error of the main process) there.
> 
> FTR, the implementation in Tramp is different from what is described
> here. And honestly, I even don't know, how to implement these two
> processes for the remote case.
> 
> The current implementation in Tramp redirects stderr to a temporary
> file, if it is separate from stdout. This temprary file is associated
> with the :stderr buffer, and it runs auto-revert-mode. Maybe not very
> elegant, but working so far.
> 
> I don't know whether we shall document this different behavior, or
> whether we shall find an implementation in Tramp for what is
> described. For the latter, I would need help, as said. Or at least ideas.

I think we should at least qualify the above description with its
being accurate for local processes only.

Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

[Michael Albinus]

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Eli Zaretskii <eliz@gnu.org> writes:

Hi Eli,

>> I don't know whether we shall document this different behavior, or
>> whether we shall find an implementation in Tramp for what is
>> described. For the latter, I would need help, as said. Or at least ideas.
>
> I think we should at least qualify the above description with its
> being accurate for local processes only.

Like this?


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: Type: text/x-patch, Size: 1399 bytes --]

*** /tmp/ediffEO055I	2019-04-23 09:08:54.501926412 +0200
--- /home/albinus/src/emacs/doc/lispref/processes.texi	2019-04-23 09:05:04.977767519 +0200
***************
*** 734,740 ****

  Depending on the implementation of the file name handler, it might not
  be possible to apply @var{filter} or @var{sentinel} to the resulting
! process object.  @xref{Filter Functions}, and @ref{Sentinels}.

  Some file name handlers may not support @code{make-process}.  In such
  cases, this function does nothing and returns @code{nil}.
--- 734,743 ----

  Depending on the implementation of the file name handler, it might not
  be possible to apply @var{filter} or @var{sentinel} to the resulting
! process object.  The @code{:stderr} argument cannot be a pipe; if it
! is a buffer a different implementation will be used to show the buffer
! contents.  @xref{Filter Functions}, @ref{Sentinels}, and
! @ref{Accepting Output}.

  Some file name handlers may not support @code{make-process}.  In such
  cases, this function does nothing and returns @code{nil}.
***************
*** 1908,1913 ****
--- 1911,1919 ----
  (while (accept-process-output stderr-process))
  @end example

+ Reading pending standard error from a process running on a remote host
+ is not possible this way.
+
  @node Processes and Threads
  @subsection Processes and Threads
  @cindex processes, threads

Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Cc: emacs-devel@gnu.org,  phst@google.com
> Date: Tue, 23 Apr 2019 09:11:23 +0200
> 
> Like this?

Maybe.  But what do you mean by "different implementation" here:

> ! process object.  The @code{:stderr} argument cannot be a pipe; if it
> ! is a buffer a different implementation will be used to show the buffer
> ! contents.     ^^^^^^^^^^^^^^^^^^^^^^^^

This sounds vague and begs questions.  Can we be more clear?

Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

> Maybe.  But what do you mean by "different implementation" here:
>
>> ! process object.  The @code{:stderr} argument cannot be a pipe; if it
>> ! is a buffer a different implementation will be used to show the buffer
>> ! contents.     ^^^^^^^^^^^^^^^^^^^^^^^^
>
> This sounds vague and begs questions.  Can we be more clear?

I don't believe implementation details belong into that manual. What about

The @code{:stderr} argument cannot be a pipe process, file name handlers
do not support pipe processes for this.  A buffer as @code{:stderr}
argument is accepted, its contents is shown without the use of pipe processes.

Best regards, Michael.

Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Cc: phst@google.com,  emacs-devel@gnu.org
> Date: Tue, 23 Apr 2019 14:05:38 +0200
> 
> The @code{:stderr} argument cannot be a pipe process, file name handlers
> do not support pipe processes for this.  A buffer as @code{:stderr}
> argument is accepted, its contents is shown without the use of pipe processes.

SGTM, thanks.

Re: master 3b4e312: Improve documentation around standard error pipes (Bug#35328).

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

>> The @code{:stderr} argument cannot be a pipe process, file name handlers
>> do not support pipe processes for this.  A buffer as @code{:stderr}
>> argument is accepted, its contents is shown without the use of pipe processes.
>
> SGTM, thanks.

Pushed to master.

Best regards, Michael.