Automatic Login via shell ?

[yaq-cc]

Hi code-server team,

This is about some linux oriented scripting automation. My code-server instance runs on a pre-emptible compute engine instance. Because of this I want to provide a shutdown script which uses linux's wall program to alert all logged in users that a pre-emption request was issued.

wall "Pre-emption detected. Please save your work!"

For the wall command to work, the user must set mesg y and must be logged in to the shell. The setting of mesg to y is done via the user's ~/.profile. My current problem is that I can't script the "login". I tried adding a sudo login -f $USER but this didn't work. instead it logged the user into the same shell over and over and over nonstop.

I have two questions:

(a) How would I go about logging a shell user in automatically and
(b) How can I perform a shell "teardown" such that if I close a shell via exit or closing the shell the user is then logged out of that shell..?

Thank you!

[jsjoeio]

Hmm... I don't know if you can script the login 🤔 Only thought that comes to mind is disabling the login with --auth none but that's probably not what you want.

cc @oxy @code-asher any ideas?

[code-asher]

I have not tested any of this but here are my thoughts.

(a) How would I go about logging a shell user in automatically

You could use your current method but detect if you are already in a login shell in order to avoid the loop.

Bash will set login_shell but other shells may be different:

if ! shopt -q login_shell ; then
  sudo login -f "$USER"
fi

Another idea is to change a setting in code-server that makes the shell spawn as a login shell by adding a flag. For Bash this flag is --login (or -l). For example by adding this to the settings file:

"terminal.integrated.shellArgs.linux": ["--login"]

(b) How can I perform a shell "teardown" such that if I close a shell via exit or closing the shell the user is then logged out of that shell..?

If I understand correctly you want exit to close out completely rather than dropping back to the non-login shell?

If you use the first method above you can add exec which will replace the current shell (exec sudo login -f "$USER").

If you use the second method nothing further needs to be done.

[code-asher]

I had the if reversed, edited above but here it is for any email users:

if ! shopt -q login_shell ; then
  sudo login -f "$USER"
fi