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

love it!

On my system, by default the pstree command sorts children by name, and I end up with this, which fails:

x-terminal-emul(5525)-+-bash(5527)
                      `-x-terminal-emul(5526)

It can be fixed by adding the -n argument to pstree:

  TREE=$(pstree -lpAn $PID | tail -n 1)

I updated the script to get CWD more reliable (for my use case).
For instance, it uses current working directory of foreground Vim instance, but if Vim is stopped (Bash's job control), it uses the current working directory of its parent shell.

The patch for tmux (of @TiddoLangerak) is not incorporated.

you can also get the information from i3-msg (as long as you terminal is able to update name/title with the path)
#!/bin/bash
cd "$(i3-msg -t get_tree | jq -r '.nodes | .[].nodes | .[].nodes | .[].nodes | .[].nodes | .[] | select( .focused==true) | [.name]' 2>&1 | sed -e '2!d;s/^.*://g;s/"$//g' | sed -e "s|^~|${HOME}|g")" || cd ~
/path/to/your/terminal

I also updated the script with inspiration of @TiddoLangerak's version to get it more reliable for my use case (gnome terminal + tmux), it takes advantage of the #{pane_active} functionality within tmux list-panes which means it's not necessary to hunt for the specific tmux PID. It also uses head for the pstree command because my tmux sessions seemed to be at the top of the tree.

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