Display information about windows. See also:
xprop,xkill. More information: https://www.x.org/releases/current/doc/man/man1/xwininfo.1.xhtml.
xwininfo
xwininfo -tree -root
xwininfo -id {{id}}
xwininfo -name {{name}}
xwininfo -tree -root | grep {{keyword}} | head -1 | perl -ne 'print $1 if /(0x[\da-f]+)/ig;'