How to make zsh detect if terminal session is run inside nvim's :term

Question

I were following the Modern Vim book by Drew Neil. In tip 20 he writes:

At a glance, you may not be able to tell whether a shell is running within a terminal buffer or outside of Neovim. In this tip, you’ll find out how you can customize the prompt for your shell so that it appears differently inside of a terminal buffer.

. . .

When Neovim starts up, it sets the $NVIM_LISTEN_ADDRESS environment variable. In the start up script for your shell, you can test for the presence of this variable. If $NVIM_LISTEN_ADDRESS is set, then you can assume that the shell is running inside of a terminal buffer. Try adding this snippet to your bashrc file:

if [ -n "$NVIM_LISTEN_ADDRESS" ]; then
    export PS1="» "
else
    export PS1="\$ "
fi

I found that $NVIM_LISTEN_ADDRESS variable is deprecated. I tried to echo it in neovim session, it is empty.

So there is a question, how to detect if zsh or bash session is run inside nvim? (:term command)

Answer 1

You can check using the following variables:

• $NVIM/$VIM
• $VIMRUNTIME

those are usually set by the running Vim/Neovim to detect from where to load the initial runtime files. However, for some rare cases (e.g. when Vim/Neovim is not able to figure this out itself), you may set those variable to point Vim/Neovim from where to load its configuration. But usually this should not be necessary.

Therefore Vim also provides the $VIM_TERMINAL variable, exactly for this purpose, which also gives you the main Vim version under which the shell is run. See :h terminal-unix