XmStringGetNextComponent(3) on Linux
The text df872944c8b9, 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 returns the type and value of the next component in a compound string "XmStringGetNextComponent" "compound string functions" "XmStringGetNextComponent"