* bug#24287: Process filters received stderr output, not documented @ 2016-08-22 17:35 Paul A. Steckler 2016-08-22 18:23 ` Eli Zaretskii 0 siblings, 1 reply; 8+ messages in thread From: Paul A. Steckler @ 2016-08-22 17:35 UTC (permalink / raw) To: 24287 The documentation for Process Filter Functions mentions that process filters receive the standard output from their associated processes. It does not mention that the filters also receive standard error output. In GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9) of 2016-04-17 on lgw01-04, modified by Debian System Description: Linux Mint 18 Sarah Configured using: `configure --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2' 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro'' Important settings: value of $LANG: en_US.UTF-8 locale-coding-system: utf-8-unix Major mode: Fundamental Minor modes in effect: tooltip-mode: t electric-indent-mode: t mouse-wheel-mode: t tool-bar-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t buffer-read-only: t line-number-mode: t transient-mark-mode: t Recent messages: Loading /etc/emacs/site-start.d/50cmake-data.el (source)...done Loading /etc/emacs/site-start.d/50dictionaries-common.el (source)... Loading debian-ispell... Loading /var/cache/dictionaries-common/emacsen-ispell-default.el (source)...done Loading debian-ispell...done Loading /var/cache/dictionaries-common/emacsen-ispell-dicts.el (source)...done Loading /etc/emacs/site-start.d/50dictionaries-common.el (source)...done Loading /etc/emacs/site-start.d/51tuareg-mode.el (source)...done For information about GNU Emacs and the GNU system, type C-h C-a. Making completion list... Load-path shadows: /usr/share/emacs24/site-lisp/cmake-data/cmake-mode hides /usr/share/emacs/site-lisp/cmake-mode /usr/share/emacs/24.5/site-lisp/debian-startup hides /usr/share/emacs/site-lisp/debian-startup Features: (shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util help-fns mail-prsvr mail-utils help-mode easymenu xterm time-date package epg-config tooltip electric uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment lisp-mode prog-mode register page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock syntax facemenu font-core frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew greek romanian slovak czech european ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer nadvice loaddefs button faces cus-face macroexp files text-properties overlay sha1 md5 base64 format env code-pages mule custom widget hashtable-print-readable backquote make-network-process dbusbind gfilenotify dynamic-setting system-font-setting font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs) Memory information: ((conses 16 82441 5872) (symbols 48 19084 0) (miscs 40 71 124) (strings 32 11704 3827) (string-bytes 1 311934) (vectors 16 7574) (vector-slots 8 345765 28255) (floats 8 66 515) (intervals 56 211 1) (buffers 960 13) (heap 1024 17669 1772)) ^ permalink raw reply [flat|nested] 8+ messages in thread
* bug#24287: Process filters received stderr output, not documented 2016-08-22 17:35 bug#24287: Process filters received stderr output, not documented Paul A. Steckler @ 2016-08-22 18:23 ` Eli Zaretskii 2016-08-22 18:38 ` Clément Pit--Claudel ` (2 more replies) 0 siblings, 3 replies; 8+ messages in thread From: Eli Zaretskii @ 2016-08-22 18:23 UTC (permalink / raw) To: Paul A. Steckler; +Cc: 24287 > From: "Paul A. Steckler" <steck@stecksoft.com> > Date: Mon, 22 Aug 2016 13:35:25 -0400 > > The documentation for Process Filter Functions mentions that process > filters receive the standard output from their associated processes. It > does not mention that the filters also receive standard error output. That is described in the parent section: It is impossible to separate the standard output and standard error streams of the subprocess, because Emacs normally spawns the subprocess inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If you want to keep the output to those streams separate, you should redirect one of them to a file—for example, by using an appropriate shell command. ^ permalink raw reply [flat|nested] 8+ messages in thread
* bug#24287: Process filters received stderr output, not documented 2016-08-22 18:23 ` Eli Zaretskii @ 2016-08-22 18:38 ` Clément Pit--Claudel 2016-08-22 19:15 ` Eli Zaretskii 2016-08-22 19:08 ` Paul A. Steckler 2016-08-23 21:47 ` Clément Pit--Claudel 2 siblings, 1 reply; 8+ messages in thread From: Clément Pit--Claudel @ 2016-08-22 18:38 UTC (permalink / raw) To: 24287 [-- Attachment #1.1: Type: text/plain, Size: 1372 bytes --] On 2016-08-22 14:23, Eli Zaretskii wrote: >> From: "Paul A. Steckler" <steck@stecksoft.com> >> Date: Mon, 22 Aug 2016 13:35:25 -0400 >> >> The documentation for Process Filter Functions mentions that process >> filters receive the standard output from their associated processes. It >> does not mention that the filters also receive standard error output. > > That is described in the parent section: > > It is impossible to separate the standard output and standard error > streams of the subprocess, because Emacs normally spawns the subprocess > inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If > you want to keep the output to those streams separate, you should > redirect one of them to a file—for example, by using an appropriate > shell command. Still, even the parent section could be confusing: The output that a subprocess writes to its standard output stream is ^^^^^^^^^^^^^^^ passed to a function called the “filter function”. The default filter function simply inserts the output into a buffer, which is called the associated buffer of the process (*note Process Buffers::). If the process has no buffer then the default filter discards the output. The highlighted section is not true, is it? Clément. [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 8+ messages in thread
* bug#24287: Process filters received stderr output, not documented 2016-08-22 18:38 ` Clément Pit--Claudel @ 2016-08-22 19:15 ` Eli Zaretskii 0 siblings, 0 replies; 8+ messages in thread From: Eli Zaretskii @ 2016-08-22 19:15 UTC (permalink / raw) To: Clément Pit--Claudel; +Cc: 24287 > Cc: Eli Zaretskii <eliz@gnu.org> > From: Clément Pit--Claudel <clement.pit@gmail.com> > Date: Mon, 22 Aug 2016 14:38:01 -0400 > > The output that a subprocess writes to its standard output stream is > ^^^^^^^^^^^^^^^ > passed to a function called the “filter function”. The default filter > function simply inserts the output into a buffer, which is called the > associated buffer of the process (*note Process Buffers::). If the process > has no buffer then the default filter discards the output. > > The highlighted section is not true, is it? Of course, it's true: the standard output _is_ passed to a filter. ^ permalink raw reply [flat|nested] 8+ messages in thread
* bug#24287: Process filters received stderr output, not documented 2016-08-22 18:23 ` Eli Zaretskii 2016-08-22 18:38 ` Clément Pit--Claudel @ 2016-08-22 19:08 ` Paul A. Steckler 2016-08-23 21:47 ` Clément Pit--Claudel 2 siblings, 0 replies; 8+ messages in thread From: Paul A. Steckler @ 2016-08-22 19:08 UTC (permalink / raw) To: Eli Zaretskii; +Cc: 24287 That's true, but the documentation for filter functions is misleading. It specifically mentions the standard output of the associated process, but neglects to mention the standard error. Also, one might not see that earlier section when looking at the documentation for filter functions. I did not see that section, in fact, when using the manual to help me write my code. -- Paul On Mon, Aug 22, 2016 at 2:23 PM, Eli Zaretskii <eliz@gnu.org> wrote: >> From: "Paul A. Steckler" <steck@stecksoft.com> >> Date: Mon, 22 Aug 2016 13:35:25 -0400 >> >> The documentation for Process Filter Functions mentions that process >> filters receive the standard output from their associated processes. It >> does not mention that the filters also receive standard error output. > > That is described in the parent section: > > It is impossible to separate the standard output and standard error > streams of the subprocess, because Emacs normally spawns the subprocess > inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If > you want to keep the output to those streams separate, you should > redirect one of them to a file—for example, by using an appropriate > shell command. ^ permalink raw reply [flat|nested] 8+ messages in thread
* bug#24287: Process filters received stderr output, not documented 2016-08-22 18:23 ` Eli Zaretskii 2016-08-22 18:38 ` Clément Pit--Claudel 2016-08-22 19:08 ` Paul A. Steckler @ 2016-08-23 21:47 ` Clément Pit--Claudel 2016-08-24 14:44 ` Eli Zaretskii 2 siblings, 1 reply; 8+ messages in thread From: Clément Pit--Claudel @ 2016-08-23 21:47 UTC (permalink / raw) To: 24287 [-- Attachment #1.1: Type: text/plain, Size: 2708 bytes --] On 2016-08-22 14:23, Eli Zaretskii wrote: >> From: "Paul A. Steckler" <steck@stecksoft.com> >> Date: Mon, 22 Aug 2016 13:35:25 -0400 >> >> The documentation for Process Filter Functions mentions that process >> filters receive the standard output from their associated processes. It >> does not mention that the filters also receive standard error output. > > That is described in the parent section: > > It is impossible to separate the standard output and standard error > streams of the subprocess, because Emacs normally spawns the subprocess > inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If > you want to keep the output to those streams separate, you should > redirect one of them to a file—for example, by using an appropriate > shell command. Hi Eli, Am I misunderstanding something? This section sounds misleading, at least for Emacs 25 (I'm not sure about Emacs 24). The documentation of make-process (which is new in Emacs 25, right?) says: :stderr STDERR Associate STDERR with the standard error of the process. STDERR is either a buffer or a pipe process created with ‘make-pipe-process’. The docstring of start-process was updated accordingly: If you want to separate standard output from standard error, use ‘make-process’ or invoke the command through a shell and redirect one of them using the shell syntax. Both of these suggest that the impossibility that the manual mention only applies to the pty case (the manual recommends against using PTYs for non-user-facing processes anyway). What about something like this: It is impossible to separate the standard output and standard error streams of a subprocess spawned inside a pseudo-TTY, as pseudo-TTYs have only one output channel. If you want to keep the output to those streams separate, you should either use `make-process' with the :stderr argument, or redirect one of the streams to a file—for example, by using start-process-shell-command with an appropriate redirection. Additionally, we could update the documentation of make-process: right now, it starts with "This function is like ‘start-process’, but takes keyword arguments.", but from what I understand it can actually do more than start-process. What about this: This function is like ‘start-process’, but takes keyword arguments, and can separate output to standard output and standard error. Btw, was there a way in Emacs 24 to separate these streams if the process was run after setting process-connection-type to nil? (I can't think of one). Cheers, Clément. [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 8+ messages in thread
* bug#24287: Process filters received stderr output, not documented 2016-08-23 21:47 ` Clément Pit--Claudel @ 2016-08-24 14:44 ` Eli Zaretskii 2016-08-24 15:18 ` Clément Pit--Claudel 0 siblings, 1 reply; 8+ messages in thread From: Eli Zaretskii @ 2016-08-24 14:44 UTC (permalink / raw) To: Clément Pit--Claudel; +Cc: 24287-done > From: Clément Pit--Claudel <clement.pit@gmail.com> > Date: Tue, 23 Aug 2016 17:47:16 -0400 > > > That is described in the parent section: > > > > It is impossible to separate the standard output and standard error > > streams of the subprocess, because Emacs normally spawns the subprocess > > inside a pseudo-TTY, and a pseudo-TTY has only one output channel. If > > you want to keep the output to those streams separate, you should > > redirect one of them to a file—for example, by using an appropriate > > shell command. > > Hi Eli, > > Am I misunderstanding something? This section sounds misleading, at least for Emacs 25 (I'm not sure about Emacs 24). The documentation of make-process (which is new in Emacs 25, right?) says: > > :stderr STDERR > Associate STDERR with the standard error of the process. > STDERR is either a buffer or a pipe process created with > ‘make-pipe-process’. > > The docstring of start-process was updated accordingly: > > If you want to separate standard output from standard error, use > ‘make-process’ or invoke the command through a shell and redirect > one of them using the shell syntax. > > Both of these suggest that the impossibility that the manual mention only applies to the pty case (the manual recommends against using PTYs for non-user-facing processes anyway). What about something like this: > > It is impossible to separate the standard output and standard error streams > of a subprocess spawned inside a pseudo-TTY, as pseudo-TTYs have only one > output channel. If you want to keep the output to those streams separate, > you should either use `make-process' with the :stderr argument, or redirect > one of the streams to a file—for example, by using > start-process-shell-command with an appropriate redirection. > > Additionally, we could update the documentation of make-process: right now, it starts with "This function is like ‘start-process’, but takes keyword arguments.", but from what I understand it can actually do more than start-process. What about this: > > This function is like ‘start-process’, but takes keyword arguments, and can > separate output to standard output and standard error. Actually, the situation was much worse than those minor changes could handle. The documentation of process-related APIs was not reviewed in its entirety for quite some time, and as result bit-rotted quite a lot. I fixed that. This is what happens and will continue to happen if people will not volunteer to review documentation during the pretest, certainly when a major version is about to be released. For Emacs 25.1, only a single individual volunteered, and a single *.texi file was reviewed. I expect the accuracy and the overall quality of our documentation to go downhill if we don't see more volunteers. > Btw, was there a way in Emacs 24 to separate these streams if the process was run after setting process-connection-type to nil? (I can't think of one). No, I don't think so. ^ permalink raw reply [flat|nested] 8+ messages in thread
* bug#24287: Process filters received stderr output, not documented 2016-08-24 14:44 ` Eli Zaretskii @ 2016-08-24 15:18 ` Clément Pit--Claudel 0 siblings, 0 replies; 8+ messages in thread From: Clément Pit--Claudel @ 2016-08-24 15:18 UTC (permalink / raw) To: Eli Zaretskii; +Cc: 24287-done [-- Attachment #1.1: Type: text/plain, Size: 303 bytes --] On 2016-08-24 10:44, Eli Zaretskii wrote: > Actually, the situation was much worse than those minor changes could > handle. The documentation of process-related APIs was not reviewed in > its entirety for quite some time, and as result bit-rotted quite a > lot. I fixed that. Great, thanks! [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2016-08-24 15:18 UTC | newest] Thread overview: 8+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2016-08-22 17:35 bug#24287: Process filters received stderr output, not documented Paul A. Steckler 2016-08-22 18:23 ` Eli Zaretskii 2016-08-22 18:38 ` Clément Pit--Claudel 2016-08-22 19:15 ` Eli Zaretskii 2016-08-22 19:08 ` Paul A. Steckler 2016-08-23 21:47 ` Clément Pit--Claudel 2016-08-24 14:44 ` Eli Zaretskii 2016-08-24 15:18 ` Clément Pit--Claudel
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