I wrote this (rather ugly) script to find the command to execute a running application by clicking on it. It uses xprop to get the "clicking interface" and to get information about the selected window:

#!/bin/bash



xprop > ./tmp



chk_desk=`grep -c "_NET_WM_DESKTOP_FILE(STRING)" ./tmp` #Checks whether application has a corresponding .desktop file. The '-c' counts the number of matches.



if [ $chk_desk -ne 0 ] ; then

    desk_line=`grep "_NET_WM_DESKTOP_FILE(STRING)" ./tmp` #Extract line containing .desktop path 

    desk_path=${desk_line/"_NET_WM_DESKTOP_FILE(STRING) = "/} #Extract only the .desktop path

    desk_path=${desk_path//"/} #Removes quotes

    exe_line=`grep "Exec=" $desk_path | head -n1`

    exe=${exe_line/"Exec="/}

else #If .desktop doesn't exist, it uses the PID to find the executable

    pid_line=`grep "_NET_WM_PID(CARDINAL)" ./tmp` 

    pid=${pid_line/"_NET_WM_PID(CARDINAL) = "/}

    exe_path=`readlink -f /proc/$pid/exe`

    exe=${exe_path//usr/bin//}

fi



echo $exe



rm ./tmp



exit 0

In case you are wondering, I could not have used only the PID for matching since /proc/$pid/exe gives you the path of the "real" executable, or of the underlying service running the program. So if you used it on say 'geogebra', the script would output java instead. Or in the case of Firefox you would get the path /usr/lib/firefox/firefox, which I suppose is where the actual firefox executable exists, which means the /usr/bin/firefox points to it.

While firefox is not a big problem (you could use the "real" executable), for the java based applications the .desktop file is needed to get the command to run the actual application and not a blank java session.

This script, of course, will only work if you are using X as your display server (since it uses xprop). I'm sure there must be a way to make the script cleaner, though my main problem was having to create many variables to hold the grep line outputs and the multiple substitutions.