Re: Proposal for extending set-process-filter

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> > 3) a file name for output.
>> Can be handled by (1) just fine.  What would you use it for (other than
>> /dev/null which is rather special since append is the same as overwrite)?
> Consistency with the BUFFER argument of start-process (which would be
> pretty much the same as the FILTER function, with the exception that
> it establishes a control buffer that is the default for process
> output, that will list the process as one of its processes, and that
> will kill the process if the buffer gets killed).  Also efficiency:
> redirecting a file descriptor to a file does not require Emacs
> processing power.  It also does not require conversion into multibyte
> strings and back and so on.

AFAIK, you can't do such a redirection after the exec.  I.e. it has to be an
argument of `start-process' rather than set-process-filter.

>> Output-appending can be done via a filter-function.
> Not really.  An open in append mode will also append at the end if
> the file gets extended by a different process.  That's pretty hard to
> do with a filter function.  One could start the file descriptor list
> with
> :append t
> or so, however.

I thought the `append' arg of write-region did it right.

>> What is still missing is the ability to open more file descriptors
>> than stdin, stdout, stderr.
> Item 5) above was supposed to cater for that.

But for the same reason as above I don't think this can be done in
set-process-filter: it has to be done before the `exec'.


        Stefan