x11 - Is there a linux command to determine the window IDs associated with a given process ID?

Question

Given a process iD of XX, I'd like to have a list of any window id's where _NET_WM_PID = XX. Even better would be the oldest still active window id if possible.

I'm very new to linux, but what I'm trying to do is create a script that would take a command line, and see if there's a windows already open belonging to a process invoked with that same command line. If so, just set focus to that window, otherwise execute the command line to get a new process going. My intention is to use this in my ubuntu desktop, where I'll hook this script into my easystroke mouse gesture commands, so that, for example, every time I gesture for gmail I don't get a brand new gmail session, I just get brought to my existing gmail chrome app window. Perhaps there's a much easier way to go about all this, but I haven't found my way to it yet.

With help, I've figured out how find a PID for a command line with pgrep and how to set focus to a window handle with wmctrl, but I'm stuck on getting from PID to window ID.

Answer 1

xwininfo and xprop permits to retrieve what you want, but it is a little tricky.

xwininfo permits to retrieve all known windows, and xprop to query X about a single window ID for your _NET_WM_PID parameter.

So far, a hacky way to do it would be:

#!/bin/sh

findpid=$1

known_windows=$(xwininfo -root -children|sed -e 's/^ *//'|grep -E "^0x"|awk '{ print $1 }')

for id in ${known_windows}
do
    xp=$(xprop -id $id _NET_WM_PID)
    if test $? -eq 0; then
        pid=$(xprop -id $id _NET_WM_PID|cut -d'=' -f2|tr -d ' ')

        if test "x${pid}" = x${findpid}
        then
            echo "Windows Id: $id"
        fi
    fi
done

Result:

mycroft:~ $ ./find_windows.sh 1919
Windows Id: 0x1800748
Windows Id: 0x181b221
Windows Id: 0x1803ad5
Windows Id: 0x181f681
Windows Id: 0x181f658
Windows Id: 0x180006d
Windows Id: 0x1800003
Windows Id: 0x1800001
Windows Id: 0x180001e

As you will see, a single process may have a certain number of known windows, even if you see only one on your screen.

Maybe you should get these tools sources in order to make what you want.