mjhjmtu

I am trying to figure out a way to detect whether the current terminal/connection (and under a tmux session as well) is through mosh or not.

From this thread, I found which pseudo-terminal session I am currently on:

$ tty
/dev/pts/69

So, I need to some information of the process that spawned this pseudo-terminal, or owns this tty as a children. With the information, perhaps I might be able to determine whether it is from sshd or mosh. But how can I do that?

Another challenge: If the current shell is under tmux, the retrieved tty might not match the sshd/mosh-server information since tmux also allocates another pseudo-terminal. Regardless of how the tmux session was created, I'll need to distinguish my current connection is from SSH or mosh. How will it be possible?

Some trials:

(1) For SSH, it was possible to find the sshd process that matches the tty:

$ ps x | grep sshd | grep 'pts/27'
 5270 ? S 0:00 sshd: wookayin@pts/27

So I can know the current connection is through SSH. However, through mosh, I could not find any relevant information.

(2) Using environment variables like SSH_CLIENT or SSH_TTY might not work because both ssh/mosh set these variables, and it is even wrong inside a tmux session.

I have come up with a decent solution to this, and wrapped it as a simple script: is_mosh.

The idea is quite simple: (i) to find the tmux client that is attached to the current tmux session, and then (ii) to search its ancestor processes to find if there is a mosh process.

It might not be complete, depending on environments, but I could succesfully detect and apply 24-bit color feature only if it's not running under mosh (as mosh doesn't support 24-bit colors). Here is a solution.