Bash script for i3 to run a terminal in the same working directory as the current focused application

i3-shell.sh

#!/bin/bash
# i3 thread: https://faq.i3wm.org/question/150/how-to-launch-a-terminal-from-here/?answer=152#post-id-152

CMD=xterm
CWD=''

# Get window ID
ID=$(xdpyinfo | grep focus | cut -f4 -d " ")

# Get PID of process whose window this is
PID=$(xprop -id $ID | grep -m 1 PID | cut -d " " -f 3)

# Get last child process (shell, vim, etc)
if [ -n "$PID" ]; then
  TREE=$(pstree -lpA $PID | tail -n 1)
  PID=$(echo $TREE | awk -F'---' '{print $NF}' | sed -re 's/[^0-9]//g')

  # If we find the working directory, run the command in that directory
  if [ -e "/proc/$PID/cwd" ]; then
    CWD=$(readlink /proc/$PID/cwd)
  fi
fi
if [ -n "$CWD" ]; then
  cd $CWD && $CMD
else
  $CMD
fi

Be aware that you can use the process' tgpid to find the foreground process of the terminal. This is more reliable and avoids having to look through the process' children. It's what I did in https://github.com/slakkenhuis/scripts/blob/master/xcwd.sh