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

x-cwd-exec.sh

#!/usr/bin/env bash


# Based on 'i3' thread [1] and Github Gist [2]:
#   [1] https://faq.i3wm.org/question/150/how-to-launch-a-terminal-from-here/?answer=152#post-id-152 
#   [2] https://gist.github.com/viking/5851049


find_cwd_of_forground_process() {
    local pid="$1"
    local cwd

    for pid in `find_childs "$pid"`; do
        pid="`find_forground_pid "$pid"`" ||
        continue
        [ "$pid" -ne -1 ] ||
        continue
        # Use this PID if there is a working directory specified.
        [ -e "/proc/$pid/cwd" ] ||
        continue
        readlink "/proc/$pid/cwd"
        return 0
    done
    return 1
}

find_childs() {
    local pid="$1"

    pstree -lpATn "$pid" |
    grep -oP '\(\K[^)]+(?=\))'
}

find_forground_pid() {
    local pid="$1"

    ps -ho tpgid "$pid" |
    sed 's/\s//g'
}


# Get window ID.
ID="$(xdpyinfo | grep focus | cut -f4 -d " ")"
# Get PID of process whose window this is.
PID="$(xprop -id "$ID" | grep -m 1 PID | cut -d " " -f 3)"
# Get CWD of first forground process within its childs.
CWD="$(find_cwd_of_forground_process "$PID")"
if [ -n "$CWD" ]; then
    cd "$CWD"
fi &&
exec "$@"

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.

Be aware that you need to call the script with the executable (including its arguments) as argument now (e.g. x-cwd-exec.sh urxvt -bg red).

It lasts quite long if firefox is active (with a lot of threads). Hence I ignore threads for now (option -T for pstree),