Writing to STDOUT from elisp

Writing to STDOUT from elisp

[Craig Muth]

Is there a way to have elisp send a string to the STDOUT of the main
emacs process?  So that it appears in the calling shell I launched
emacs from?  (So I'll see it when I suspend or quit?)

Ty!
--Craig

Re: Writing to STDOUT from elisp

[Mathias Dahl]

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Not sure this can be done without using batch mode. This is a small test I
just did on w32:

c:\> emacs.exe --batch --eval "(message """Test""")"
Test



On Sun, Jun 29, 2014 at 12:51 AM, Craig Muth <craig.muth@gmail.com> wrote:

> Is there a way to have elisp send a string to the STDOUT of the main
> emacs process?  So that it appears in the calling shell I launched
> emacs from?  (So I'll see it when I suspend or quit?)
>
> Ty!
> --Craig
>
>

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Re: Writing to STDOUT from elisp

[Stephen J. Turnbull]

See `princ' and friends.

Mathias Dahl writes:
 > Not sure this can be done without using batch mode. This is a small test I
 > just did on w32:
 > 
 > c:\> emacs.exe --batch --eval "(message """Test""")"
 > Test
 > 
 > 
 > 
 > On Sun, Jun 29, 2014 at 12:51 AM, Craig Muth <craig.muth@gmail.com> wrote:
 > 
 > > Is there a way to have elisp send a string to the STDOUT of the main
 > > emacs process?  So that it appears in the calling shell I launched
 > > emacs from?  (So I'll see it when I suspend or quit?)
 > >
 > > Ty!
 > > --Craig
 > >
 > >

Re: Writing to STDOUT from elisp

[Eli Zaretskii]

> From: Mathias Dahl <mathias.dahl@gmail.com>
> Date: Tue, 8 Jul 2014 08:36:18 +0200
> Cc: emacs-devel@gnu.org
> 
> Not sure this can be done without using batch mode. This is a small test I
> just did on w32:
> 
> c:\> emacs.exe --batch --eval "(message """Test""")"
> Test

'message' writes to stderr, not to stdout, so this is not what the OP
wanted.

Stephen's suggestion is better: it does write to stdout.

Re: Writing to STDOUT from elisp

[Andreas Schwab]

Eli Zaretskii <eliz@gnu.org> writes:

> Stephen's suggestion is better: it does write to stdout.

It writes to the echo area.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Re: Writing to STDOUT from elisp

[Stephen J. Turnbull]

Andreas Schwab writes:
 > Eli Zaretskii <eliz@gnu.org> writes:
 > 
 > > Stephen's suggestion is better: it does write to stdout.
 > 
 > It writes to the echo area.

See `standard-output'.

Re: Writing to STDOUT from elisp

[Andreas Schwab]

"Stephen J. Turnbull" <stephen@xemacs.org> writes:

> Andreas Schwab writes:
>  > Eli Zaretskii <eliz@gnu.org> writes:
>  > 
>  > > Stephen's suggestion is better: it does write to stdout.
>  > 
>  > It writes to the echo area.
>
> See `standard-output'.

Yes.  Did you look it up?

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Writing to STDOUT from elisp

[Craig Muth]

You can get princ to write to "standard-output", meaning the echo
area.  I'm looking to write to the stdout of the whole process, so the
output shows up in the terminal you launched emacs in.  So when you
exit emacs, you'll see the text in the shell.

I've asked around and am pretty sure elisp can't do this.  I may have
found the one elemental thing that elisp can't do :)

--Craig


On Tue, Jul 8, 2014 at 11:59 AM, Andreas Schwab <schwab@suse.de> wrote:
> "Stephen J. Turnbull" <stephen@xemacs.org> writes:
>
>> Andreas Schwab writes:
>>  > Eli Zaretskii <eliz@gnu.org> writes:
>>  >
>>  > > Stephen's suggestion is better: it does write to stdout.
>>  >
>>  > It writes to the echo area.
>>
>> See `standard-output'.
>
> Yes.  Did you look it up?
>
> Andreas.
>
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."

Re: Writing to STDOUT from elisp

[Eli Zaretskii]

> Date: Tue, 8 Jul 2014 18:50:23 -0700
> From: Craig Muth <craig.muth@gmail.com>
> Cc: "Stephen J. Turnbull" <stephen@xemacs.org>, Mathias Dahl <mathias.dahl@gmail.com>, 
> 	Eli Zaretskii <eliz@gnu.org>, emacs-devel@gnu.org
> 
> You can get princ to write to "standard-output", meaning the echo
> area.  I'm looking to write to the stdout of the whole process, so the
> output shows up in the terminal you launched emacs in.  So when you
> exit emacs, you'll see the text in the shell.
> 
> I've asked around and am pretty sure elisp can't do this.  I may have
> found the one elemental thing that elisp can't do :)

Please show what did you try and why do you think it didn't do what
you want.

Re: Writing to STDOUT from elisp

[Stephen J. Turnbull]

Andreas Schwab writes:

 > > See `standard-output'.
 > 
 > Yes.  Did you look it up?

Hm.  This is harder than I thought.  In XEmacs at least, it's trivial
in -batch mode[1], but interactively the initial stream console gets
deleted, and that dead console gets in the way of output to stdout.


Footnotes: 
[1]  Somehow xemacs -batch -f dunnet on the console just feels more
natural than playing in a GUI window. ;-)

Re: Writing to STDOUT from elisp

[Andreas Schwab]

"Stephen J. Turnbull" <stephen@xemacs.org> writes:

> Andreas Schwab writes:
>
>  > > See `standard-output'.
>  > 
>  > Yes.  Did you look it up?
>
> Hm.  This is harder than I thought.  In XEmacs at least, it's trivial
> in -batch mode[1],

In batch mode the echo area is the stdout.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Re: Writing to STDOUT from elisp

[Eli Zaretskii]

> Date: Tue, 8 Jul 2014 18:50:23 -0700
> From: Craig Muth <craig.muth@gmail.com>
> Cc: "Stephen J. Turnbull" <stephen@xemacs.org>, emacs-devel@gnu.org,
> 	Eli Zaretskii <eliz@gnu.org>, Mathias Dahl <mathias.dahl@gmail.com>
> 
> You can get princ to write to "standard-output", meaning the echo
> area.  I'm looking to write to the stdout of the whole process, so the
> output shows up in the terminal you launched emacs in.  So when you
> exit emacs, you'll see the text in the shell.

You can do that with "emacs -batch", where princ writes to stdout.

If you want to do this in an interactive session, please tell what
exactly are you trying to do and why.  For example, is this only
needed when you exit Emacs, or do you want to be able to write to
stdout and then continue to run Emacs for a while (and why)?

Re: Writing to STDOUT from elisp

[Craig Muth]

> If you want to do this in an interactive session

Yes, in an interactive session.

> please tell what
> exactly are you trying to do and why.  For example, is this only
> needed when you exit Emacs

Doing it when exiting emacs would work.  The best way to see what I'm
trying to do is to watch the first 20 seconds of the video on
http://xsh.org.  Xsh runs in emacs (transparently for most users,
since most key shortcuts are redefined).  I'm using a work-around to
do the printing for now.  One possible work-around is to making xsh be
a bash script (or function) that runs emacs and then prints text it
finds in a file temp file to stdout.  But it would be nice if I could
do it without that step.

--Craig

Re: Writing to STDOUT from elisp

[Eli Zaretskii]

> Date: Wed, 9 Jul 2014 22:40:09 -0700
> From: Craig Muth <craig.muth@gmail.com>
> Cc: Andreas Schwab <schwab@suse.de>, "Stephen J. Turnbull" <stephen@xemacs.org>, emacs-devel@gnu.org, 
> 	Mathias Dahl <mathias.dahl@gmail.com>
> 
> > If you want to do this in an interactive session
> 
> Yes, in an interactive session.
> 
> > please tell what
> > exactly are you trying to do and why.  For example, is this only
> > needed when you exit Emacs
> 
> Doing it when exiting emacs would work.

Then one way of doing this is call kill-emacs with a non-nil argument,
then wrap Emacs in a shell script that would do whatever you want
depending on the Emacs exit code.

Of course, submitting (trivial) patches for adding a command to write
to stdout would probably be welcome as well.  But please note that
sometimes Emacs is invoked with stdout redirected to some obscure
file, or even with stdout being closed/invalid.

Re: Writing to STDOUT from elisp

[Lennart Borgman]

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On Thu, Jul 10, 2014 at 5:03 PM, Eli Zaretskii <eliz@gnu.org> wrote:

>
> Of course, submitting (trivial) patches for adding a command to write
> to stdout would probably be welcome as well.  But please note that
> sometimes Emacs is invoked with stdout redirected to some obscure
> file, or even with stdout being closed/invalid.
>
> I used that very much for debugging before. Wonder if I still have that
code somewhere?

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Re: Writing to STDOUT from elisp

[Craig Muth]

If you were able to dig up that code, that would be cool.

On a related note, I'd be curious to hear anyone's feedback about Xsh
(the video at the top is the best thing too check out):

  http://xsh.org

--Craig



On Thu, Jul 10, 2014 at 8:20 AM, Lennart Borgman
<lennart.borgman@gmail.com> wrote:
> On Thu, Jul 10, 2014 at 5:03 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>>
>>
>> Of course, submitting (trivial) patches for adding a command to write
>> to stdout would probably be welcome as well.  But please note that
>> sometimes Emacs is invoked with stdout redirected to some obscure
>> file, or even with stdout being closed/invalid.
>>
> I used that very much for debugging before. Wonder if I still have that code
> somewhere?

Re: Writing to STDOUT from elisp

[Johan Bockgård]

Craig Muth <craig.muth@gmail.com> writes:

> You can get princ to write to "standard-output", meaning the echo
> area.  I'm looking to write to the stdout of the whole process, so the
> output shows up in the terminal you launched emacs in.  So when you
> exit emacs, you'll see the text in the shell.

(write-region STRING nil "/dev/stdout")

Re: Writing to STDOUT from elisp

[Eli Zaretskii]

> From: Johan Bockgård <bojohan@gnu.org>
> Date: Thu, 10 Jul 2014 21:09:40 +0200
> 
> (write-region STRING nil "/dev/stdout")

That's non-portable.

Re: Writing to STDOUT from elisp

[Johan Bockgård]

Craig Muth <craig.muth@gmail.com> writes:

> You can get princ to write to "standard-output", meaning the echo
> area.  I'm looking to write to the stdout of the whole process, so the
> output shows up in the terminal you launched emacs in.  So when you
> exit emacs, you'll see the text in the shell.

You can write to STDERR with `external-debugging-output'.

Re: Writing to STDOUT from elisp

[Thien-Thi Nguyen]

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Please find attached an old (needs love) patch to write
messages to stderr on exit.  Perhaps it can be of use.


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-- 
Thien-Thi Nguyen
   GPG key: 4C807502
   (if you're human and you know it)
      read my lisp: (responsep (questions 'technical)
                               (not (via 'mailing-list)))
                     => nil

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