+val cat : t -> string -> string
+(** list the contents of a file *)
+
+val ll : t -> string -> string
+(** list the files in a directory (long format) *)
+
+val ls : t -> string -> string array
+(** list the files in a directory *)
+
+val list_devices : t -> string array
+(** list the block devices *)
+
+val list_partitions : t -> string array
+(** list the partitions *)
+
+val pvs : t -> string array
+(** list the LVM physical volumes (PVs) *)
+
+val vgs : t -> string array