Run a command each time you suspend vim with ctrl+z

on_suspend.sh

# Current unix time in millisecond
function ms() {
  echo $(($(date +%s%N)/1000000))
}

# If we suspend vim (ctrl-z), run the on-suspend command and then
# re-foreground vim. If we exit fully, return to the shell.
function post_vim() {
  # 148 status code indicate the previous command was suspended
  if [ ! $? = 148 ]; then return; fi
  if [ 0 = "$#" ]; then
    # Not required to set the command initially, it will prompt you
    # the first time you suspend
    set_command
  else
    wrap_command $@
    post_command $@
  fi
}

# Just print some helpful information about the on-suspend command invocation
function wrap_command() {
  clear
  local before=`ms`
  bash -c "$*"
  local status="$?"
  local after=`ms`
  local dt=$(($after - $before))
  echo "[Exited with status $status after ${dt}ms]"
}

# After running the on-suspend command, prompt with options:
# - drop to a bash shell (`b` or `s`)
# - change the on-suspend command (`c`)
# - return to vim (any other key)
function post_command() {
  read -n 1 -srp "[Press 's' for shell, 'c' to change command, any other key to continue]" key
  if [ "$key" = b -o "$key" = s ]; then
    bash
    fg
    post_vim $@
  elif [ "$key" = c ]; then
    echo
    echo "New on-background command:"
    read command
    wrap_command $command
    post_command $command
  else
    fg
    post_vim $@
  fi
}

# Prompt for a new on-suspend command, then return to the loop
function set_command() {
  echo
  echo "New on-background command:"
  read command
  wrap_command $command
  post_command $command
}

function viv() {
  nvim
  post_vim $@
}