xwininfo

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;'