grdvolume(1gmt) on Linux
The text abde69456ef4, as Debian 7 (Wheezy), Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
Calculating volume under a surface within a contour
Flags it lists
-
-C -
-L -
-R -
-S -
-T -
-V -
-Z