how to distinguish ssh from scp in ~/.ssh/rc?

Question

I'd like to launch neofetch (a small utility that displays a banner) each time I log into a remote server via OpenSSH. So, I just added /usr/bin/neofetch into my ~/.ssh/rc file, and it works fine. The problem is that ~/.ssh/rc is also parsed when I scp into the server. A complete scp command works just fine, there is however a problem when I try to use the autocomplete feature of scp, when I type <Tab><Tab> so it displays the files/folders available on the remote server, example :

$ scp remote-host:/t <TAB><TAB>
\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\`\\\"\\\"\\\"\\\  
\\\ \\\$\\\$\\\:\\\ \\\ \\\ \\\ \\\ \\\ \\\$\\\$.\\\ \\\ \\\ ^[\\\[0m^[\\\[31m^[\\\[1m-^[\\\[0m^[\\\[1m\\\ \\\ \\\ \\\ \\\,d\\\$\\\$\\\'\\\  
\\\ \\\ \\\ \\\ \\\ \\\`\\\$\\\$b.\\\  
\\\ \\\,\\\$\\\$P\\\'\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\`\\\$\\\$\\\$.\\\  
\\\ \\\$\\\$P\\\ \\\ \\\ \\\ \\\ \\\ d\\\$\\\'\\\ \\\ \\\ \\\ \\\ ^[\\\[0m^[\\\[31m^[\\\[1m\\\,^[\\\[0m^[\\\[1m\\\ \\\ \\\ \\\ \\\$\\\$P\\\  
\\\'\\\,\\\$\\\$P\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\,ggs.\\\ \\\ \\\ \\\ \\\ \\\`\\\$\\\$b\\\:\\\  
\\\ \\\$\\\$\\\;\\\ \\\ \\\ \\\ \\\ \\\ Y\\\$b._\\\ \\\ \\\ _\\\,d\\\$P\\\'\\\  
^[\\\[0m^[\\\[1m\\\ \\\`\\\$\\\$b\\\ \\\ \\\ \\\ \\\ \\\ ^[\\\[0m^[\\\[31m^[\\\[1m\\\"-.__\\\  
^[\\\[0m^[\\\[1m\\\ \\\ \\\`Y\\\$\\\$\\\ 
(...)

Usually $ scp remote-host:/t <TAB><TAB> shows me the files/folders starting with /t (for example /tmp), but now it executes the neofetch banner.

Is there a way to distinguish $ ssh from $ scp in ~/.ssh/rc (to launch neofetch only when I ssh into the server, not when I scp into it) ?

Note : I don't want to launch neofetch each time I launch bash, nor each time I launch a login shell, so putting it in /etc/bash.bashrc or in /etc/profile is not an option. I only want to launch it after an SSH connection.

I did some research and tried a few things :

• Inspired by this post, I tried :

  if [ -t 0 ]; then /usr/bin/neofetch; fi

  and

  if tty > /dev/null; then /usr/bin/neofetch; fi

  But it's not working (neofetch is never launched, not even after an $ ssh)

• Inspired by that post, I also tried to use the $- environment variable to distinguish between interactive and non interactive sessions, but it doesn't work either, because ~/.ssh/rc is parsed by dash, not by bash (and $- is a bash variable)

I found however a working solution (well, sort of...). It was inspired by this post :

• On the server, in ~/.ssh/rc, I put :

  if [ ! "$LC_SCP" = "yes" ]; then /usr/bin/neofetch; fi

• On the client, I have to set an LC_SCP environment variable before the $ scp :

$ export LC_SCP=yes

$ scp -o SendEnv=LC_SCP remote-host:/t<TAB><TAB>
(works, doesn't launch neofetch)

It works, but it's cumbersomee. Isn't there a better way to distinguish between ssh and scp sessions in ~/.ssh/rc ?

Answer 1

The environment variable SSH_TTY seems to be set only when sshing, not when scping. So the following suffices (at least in my testing):

if [ -n "$SSH_TTY" ]; then /usr/bin/neofetch; fi

(For what it's worth, I guessed this by looking at the output of env | grep -i ssh.)