+test -z "$MT" && Exit 2 "<none>" "No mt command defined"
+test ! -f "$MT" && Exit 2 "<none>" "mt command ($MT) doesn't exist"
+test -z "$MTX" && Exit 2 "<none>" "No mtx command defined"
+test ! -f "$MTX" && Exit 2 "<none>" "mtx command ($MTX) doesn't exist"
+