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Date: Sun, 11 Aug 2024 12:35:39 -0600
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Subject: Re: apparent solution to Emacs multi-shell problem
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From: Brian Inglis via Cygwin <cygwin AT cygwin DOT com>
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Cc: Brian Inglis <Brian DOT Inglis AT SystematicSW DOT ab DOT ca>
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[Added Emacs to Subject to get appropriate attention]

On 2024-08-11 11:22, KARR, DAVID via Cygwin wrote:
> This is a repost with additional information. I've managed to find a fix, but I'd like to understand what happened, and perhaps clean up some ancient code.
> 
> For the last few days, I've been struggling with a problem with Cygwin Emacs after reinstalling Cygwin, which I haven't had to do for a while.
> 
> I discovered that when I create the first shell buffer, it works fine. When I create the second shell buffer, it fails with this:
> ------------------
>     bash: cannot set terminal process group (-1): Inappropriate ioctl for device
>     bash: no job control in this shell
> ----------------
> 
> After I got away from the computer for a while, I realized that I might be able to narrow this down.  I thought that this might be a problem with the small façade package I wrote over "shell" a few decades ago, but I realized that if I just start Emacs and manually switch to a buffer and run "shell" and then do that again, that is basically the same thing.  I found that that repeats the problem.
> 
> So then I looked at my .emacs file, and I noticed the following.  Note that this is another block of code that I haven't changed in many years. I know that several of these lines are obsolete now, even some that aren't causing my problem:
> ------------------
> (defun my-shell-mode-hook ()
> ;(add-hook 'comint-output-filter-functions
> ;	    'shell-strip-ctrl-m nil t)
>    (add-hook 'comint-output-filter-functions
> 	    'comint-watch-for-password-prompt nil t)
>    (setq explicit-shell-file-name "bash")
>    ;; For subprocesses invoked via the shell
>    ;; (e.g., "shell -c command")
>    (setq shell-file-name explicit-shell-file-name)
>    (ansi-color-for-comint-mode-on)
>    (shell-strip-ctrl-m)
>    (setq shell-prompt-pattern "^\[[A-z0-9]+:[A-z0-9/]+\] ")
>    (local-set-key "\C-xs" 'cycle-go-shell)
>    (local-set-key "\C-xS" 'cycle-find-shell-or-shells-buffer-list)
>    (local-set-key "\C-j" 'lfd-send-input)
>    (local-set-key [f5] 'comint-previous-matching-input-from-input)
>    (local-set-key [f12] 'compilation-shell-minor-mode)
>    )
> -----------------
> 
> For most of this, I can't even remember what it was for.  I tried commenting out portions of this and retesting, and I finally narrowed it down to the two sets of the related "file-name" variables. When I comment both of those out and retest, the problem doesn't occur.  I see that the new value of "shell-file-name" is "/bin/bash", instead of the "bash" value that I was hardcoding before.  Certainly less code is better than more code, especially if it works, but it would be useful to understand if something changed recently that might have caused that error.
> 
> I also briefly examined some of these other blocks, and I see that apparently "shell-strip-ctrl-m" is obsolete.  Is it best to have this?:
> 
>      (add-hook 'comint-output-filter-functions
> 	'comint-strip-ctrl-m nil t)

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry


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