29.1: tramp: use $SHELL environment variable to start remote shell?

[Giovanni Biscuolo]

Hello,

please is it possible to start a remote shell (and vterm) using the
program defined in the $SHELL env variable on the remote host?

Alternatively, is there a way to automatically source a remote profile
(e.g. .bash_profile) in the remote shell?

Short story long (sorry for the long details)...

I have this Emacs and TRAMP versions:

--8<---------------cut here---------------start------------->8---
(emacs-version)
"GNU Emacs 29.1 (build 1, x86_64-unknown-linux-gnu, cairo version 1.16.0)"

(tramp-version nil)
"2.6.2.0"
--8<---------------cut here---------------end--------------->8---

Installed emacs-vterm version: 0.0.2-1.c3a3a23

If I open a remote directory in dired with TRAMP and then connect to a
remote host with "M-x shell" or "M-x vterm", the default shell is
/bin/sh

I can later start my preferred shell with "$SHELL -l" so my shell
profile (e.g. .bash_profile) is sourced and all is working as expected
[1]

I need my remote profile to be loaded because all hosts I manage have
Guix [2] installed and all needed environment variables are set by the
user profile; here is an example of a "M-x shell" remote connection to a
guix host (foreign distro), the same holds for "M-x eshell":

--8<---------------cut here---------------start------------->8---

/ssh:local.biscuolo.anemone:/localhome/g/ #$ guix describe
  guix 3676e31
    repository URL: https://git.savannah.gnu.org/git/guix.git
    commit: 3676e312aaf1ce10ed1d7844e871b54e04624098
/ssh:local.biscuolo.anemone:/localhome/g/ #$ $SHELL -l
(anemone)g@anemone:~$ guix describe
Generation 9    Apr 21 2021 09:23:33    (current)
  guix 13c4a37
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 13c4a377f5a2e1240790679f3d5643385b6d7635

--8<---------------cut here---------------end--------------->8---
(as you can see, without proper environment guix is not able to run as
it should)

I know that I can customize the remote shell to use by:

1. use "C-u M-x shell" and specify the remote shell to use [3]

2. use connection related information [4] to customize "remote-shell"
per-connection (via regexp)

but 1. does not vork for vterm and 2. is too complicated for this use
case, IMO.

Ideally I would like both "M-x shell" and "M-x vterm" to just do "the
right thing" and start a remote shell using the remote $SHELL
environment variable.

Any hint please?

Happy hacking, Gio'


[1] I mean, is working in the same way I get when connecting with any
other terminal emulator

[2] some on foreign distro, other on Guix System

[3] /bin/bash on foreign distros, /run/current-system/profile/bin/bash
on Guix System

[4] 
https://www.gnu.org/software/emacs/manual/html_node/tramp/Predefined-connection-information.html



P.S.: yes, still not using eshell as I should! :-(

-- 
Giovanni Biscuolo

Xelera IT Infrastructures

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