xwd(1) on Linux
The text 00b156a9064b, as Debian 5.0 (Lenny), Debian 4.0 (Etch) shipped it.
dump an image of an X window
Flags it lists
-
-add -
-display -
-frame -
-help -
-icmap -
-id -
-name -
-nobdrs -
-out -
-root -
-screen -
-silent -
-xy