dlagtm(3) on Linux
The text 28b5a47fee3d, as Debian 3.1 (Sarge) shipped it.
perform a matrix-vector product of the form B := alpha * A * X + beta * B where A is a tridiagonal matrix of order N, B and X are N by NRHS matrices, and alpha and beta are real scalars, each of which may be 0., 1., or -1