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bug#46466: 28.0.50; Tramp hangs with bad prompt even when using /bin/sh
From: |
Erik Hetzner |
Subject: |
bug#46466: 28.0.50; Tramp hangs with bad prompt even when using /bin/sh |
Date: |
Sat, 13 Feb 2021 09:07:50 -0800 |
User-agent: |
Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (Gojō) APEL-LB/10.8 EasyPG/1.0.0 Emacs/28.0.50 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) |
Hi Michael,
On Sat, 13 Feb 2021 00:53:35 -0800,
Michael Albinus <michael.albinus@gmx.de> wrote:
>
> […]
>
> What is /bin/sh, both locally and remote? In my case, running Fedora 33,
> I see
>
> --8<---------------cut here---------------start------------->8---
> # ls -l /bin/sh
> lrwxrwxrwx. 1 root root 4 Jul 27 2020 /bin/sh -> bash
> --8<---------------cut here---------------end--------------->8---
Good question, I should have mentioned that. I have tested this on
both debian and ubuntu, where /bin/sh is linked to dash
$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 Dec 10 05:23 /bin/sh -> dash
As a follow up, I suspect that in some way this is expected behavior.
I see that the *sshx* connection method specifies the shell to run
when connecting, whereas the *ssh* connection method connects without
specifying a command, and therefore starts a default remote shell.
This suggests a fix which turns out to works. The behavior is fixed,
for me, by adding `("-o" "RemoteCommand='%l'")` to the list of
`tramp-login-args' for `tramp-methods' (see below).
It is also possible to set the PS1 value directly with this remote
command, e.g. `("-o" "RemoteCommand='PS1=\"$ \" %l'")`, which might
provide even more safety against unusual prompts.
Is this a patch that would be welcome? It would fix cases where users
had more elaborate prompts in their default shell and where /bin/sh
was a simpler shell (debian and ubuntu, at least). Unusual prompts are
more and more popular, but users to do not usually enable them for
/bin/sh. However, it might have effects that I am not aware of.
```
(add-to-list 'tramp-methods
`("ssh"
(tramp-login-program "ssh")
(tramp-login-args (("-l" "%u") ("-p" "%p") ("%c")
("-e" "none")
("-o" "RemoteCommand='%l'") ("%h")))
(tramp-async-args (("-q")))
(tramp-direct-async t)
(tramp-remote-shell ,tramp-default-remote-shell)
(tramp-remote-shell-login ("-l"))
(tramp-remote-shell-args ("-c"))))
```
best, Erik