Having a brain damaged by prolonged use of vim I even use a vi input mode for my shell. I recently switched from bash to zsh and among other niceties zsh can show which vi mode I’m currently in and update this in real time as I switch. I found out how to do this from Aaron Toponce’s blog.

To have a VIMODE variable which is updated as you switch modes, add this to your ~/.zshrc:

# set VIMODE according to the current mode (default “[i]”)
VIMODE='[i]'
function zle-keymap-select {
 VIMODE="${${KEYMAP/vicmd/[n]}/(main|viins)/[i]}"
 zle reset-prompt
}

zle -N zle-keymap-select

You can then add $VIMODE to your prompt:

# Set the prompt to “[user]@[host[ [vi mode] $ ”
PROMPT="%n@%m ${VIMODE} \\$ "