tk_messageBox(3tk) on Linux
The text 83ecc1e63173, as Debian 11 (Bullseye), Debian 10 (Buster) shipped it.
pops up a message window and waits for user response.
Flags it lists
-
-command -
-default -
-detail -
-icon -
-message -
-parent -
-title -
-type