2

I am running a remote putty session from windows to my Red Hat Enterprise Linux server.

Due to company restrictions, I am unable to change my Linux user's default shell from bash to zsh. I instead have read only access to ~./bash_profile, which executes ~/.bashrc (where I also have only read only access), which in turn executes ~/.bash_custom where I have write access. Inside ~/.bash_custom, I execute zsh to change my shell.

Including the line to execute zsh prevents the execution of any remote command provided by putty. I know this is the problem since if I comment out my execution of zsh it works fine.

I have several aliases and PATH modifications inside my zsh which I'd like to use as part of the remote command executed from putty. How can I pass the remote command from the bash shell to zsh for it to be executed there?

Stéphane Chazelas
  • 544,893
Adam Griffiths
  • 351
  • 1
    What Linux are you using? Sounds like it is one of the ones that have .profile source .bashrc because normally, .bashrc wouldn't even be read when sshing into a machine. Do you have code in your ~/.profile that makes it source .bashrc? Also, are you opening an interactive shell session or are you just trying to run a single command? – terdon Nov 21 '23 at 16:02
  • @terdon Bash reads .bashrc when invoked non-interactively over rsh or ssh (with some variation between versions and distributions, IIRC making ssh like rsh was originally a Debian patch). – Gilles 'SO- stop being evil' Nov 21 '23 at 17:09
  • I'm not sure what you're doing exactly, but this looks self-inflicted. Why would you exec zsh in .bashrc? I can't think of a good reason to do that. Why not do it in .bash_profile, so that it's only done in interactive shells? – Gilles 'SO- stop being evil' Nov 21 '23 at 17:10
  • @Gilles'SO-stopbeingevil' yes, non interactively only, that's why I asked if the OP is opening an interactive session or trying to run a single command. If not, if this is opening an interactive login shell, then they must have a profile that reads bashrc. – terdon Nov 21 '23 at 17:14
  • @terdon I am using Red Hat Enterprise Linux. I have read only access to ~/.bash_profile which then executes ~/.bashrc which I also have only read only access to which then executed ~/.bash_custom which I have write access to and which is where I run zsh – Adam Griffiths Nov 22 '23 at 09:29
  • Please add this to your question, it is very relevant. This is a non-standard setup. Sounds like you just need to wrap your $HOME/bin/zsh in code that makes sure it is only executed when running interactively. – terdon Nov 22 '23 at 09:34
  • Will do, but I'd like to preferably pass it to zsh instead because I have aliases and a different PATH in zsh that I'd like to use in my remote commands. – Adam Griffiths Nov 22 '23 at 09:49

1 Answers1

1

On some (most these days) systems, bash is configured at build time so that when run over ssh, bash reads ~/.bashrc (and corresponding system-wide file in /etc) even when run non-interactively like when running ssh some command where sshd runs bash -c 'some command'¹.

What you could do is add at the top of your ~/.bash_custom:

export SHELL="$(command -v zsh)" # tell everyone your preferred shell
case ${SSH_CONNECTION+s}:${-//[^ilc]}:$#:$SHLVL in
  (s:c:0:1) exec zsh -c -- "$BASH_EXECUTION_STRING";;
  (*:i:0:*) exec zsh;;
esac

That executes zsh with the same code when bash is run as bash -c 'some code' by sshd, and zsh alone when bash is run interactively.

You could limit that second case to cases where bash is invoked as a login shell only with:

if shopt -q login_shell; then
  exec zsh
fi

and/or only via ssh by replacing *:i:0:* with s:i:0:*

¹ Strictly speaking, it should run bash -c -- 'some command' but since there are shells where that's not supported (or not needed like in csh, fish, rc...), it doesn't.

Stéphane Chazelas
  • 544,893