XmStringHasSubstring(3) on Linux
The text 25d211ea6a07, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A compound string function that indicates whether one compound string is contained within another "XmStringHasSubstring" "compound string functions" "XmStringHasSubstring"