grdtrack(1) on Linux
The text 6debf62b2641, as Debian 2.2 (Potato) shipped it.
Sampling of a 2-D grdfile along 1-D trackline (a sequence of x,y points)
Flags it lists
-
-: -
-G -
-H -
-L -
-M -
-Q -
-R -
-S -
-V -
-bi -
-bo