[Libguestfs] [PATCH 14/27] daemon: Reimplement ‘lvs’ API in OCaml.

[Pino Toscano]

On Friday, 14 July 2017 15:39:22 CEST Richard W.M. Jones wrote:
> +let lvs_has_S_opt = lazy (
> +  let out = command "lvm" ["lvs"; "--help"] in
> +  String.find out "-S" >= 0
> +)

Could you please add the comment for this?

(* Check whether lvs has -S to filter its output.
 * It is available only in lvm2 >= 2.02.107.
 *)

> +and convert_lvm_output ?(prefix = "") out =
> +  let lines = String.nsplit "\n" out in
> +
> +  (* Skip leading and trailing ("pvs", I'm looking at you) whitespace. *)
> +  let lines = List.map String.trim lines in
> +
> +  (* Skip empty lines. *)
> +  let lines = List.filter ((<>) "") lines in
> +
> +  (* Ignore "unknown device" message (RHBZ#1054761). *)
> +  let lines = List.filter ((<>) "unknown device") lines in
> +
> +  (* Add a prefix? *)
> +  let lines = List.map ((^) prefix) lines in

A small optimization here could be to avoid the map if the prefix is
empty:

  let lines =
    if prefix <> "" then List.map ((^) prefix) lines
    else lines in

(or even not giving ?prefix a default value, and matching on None/Some)

-- 
Pino Toscano
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