Re: Adding streams for standard out and standard err

[phillip.lord@russet.org.uk (Phillip Lord)]

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: emacs-devel@gnu.org
>> From: Paul Eggert <eggert@cs.ucla.edu>
>> Date: Thu, 21 Jul 2016 16:40:10 +0200
>> 
>> On 07/21/2016 04:21 PM, Eli Zaretskii wrote:
>> >   . We already have (append-to-file START END FILENAME), which can be
>> >     used to write a buffer or a string to a file.  FILENAME can be
>> >     "/dev/stderr" on Posix platforms, for example, or it can be a real
>> >     file name.
>> 
>> Wouldn't the proposed primitives often be more efficient than 
>> append-to-file, since they would use stdio buffering?
>
> Probably.  But is performance relevant to the use cases we intend them
> to be used?

You are correct in this case, performance is irrelevant. In fact,
buffering is a bit of a pain. It took me a few minutes to work out why

(print "hello" 'stdout)

worked but

(princ "hello" 'stdout)

didn't -- the latter gets buffered.


>> Presumably people using the new primitives would know about their 
>> problems with tty and/or GUI frames, just as they know about the similar 
>> problems that append-to-file has with /dev/stderr.
>
> I'm not so sure.  But that's not the important part of my reasoning.

It's important to the "unreliable/dangerous" part of your argument.

I will add further documentation to the patch, pointing out this
potential problem.

Phil