package logs

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Cmdliner support for Logs.

See a full example.

v0.7.0 - homepage

Options for setting the report level

val level : ?env:Cmdliner.Arg.env -> ?docs:string -> unit -> Logs.level option Cmdliner.Term.t

level ?env ?docs () is a term for three Cmdliner options that can be used with Logs.set_level. The options are documented under docs (defaults to the default of

The options work as follows:

  • -v or --verbose, if it appears once, the value of the term is is Some Logs.Info and more than once Some Logs.Debug.
  • --verbosity=LEVEL, the value of the term is l where l depends on on LEVEL. Takes over the option -v.
  • -q or --quiet, the value of the term is None. Takes over the -v and --verbosity options.
  • If both options are absent the default value is Some Logs.warning

If env is provided, the default value in case all options are absent can be overridden by the corresponding environment variable.


The following example shows how to setup Logs and Fmt so that logging is performed on standard outputs with ANSI coloring if these are ttys. The command line interface provides options to control the use of colors and the log reporting level.

let hello () = (fun m -> m "Hello horrible world!")

let setup_log style_renderer level =
  Fmt_tty.setup_std_outputs ?style_renderer ();
  Logs.set_level level;
  Logs.set_reporter (Logs_fmt.reporter ());

(* Command line interface *)

open Cmdliner

let setup_log =
  Term.(const setup_log $ Fmt_cli.style_renderer () $ Logs_cli.level ())

let main () =
  match Term.(eval (const hello $ setup_log, "tool")) with
  | `Error _ -> exit 1
  | _ -> exit (if Logs.err_count () > 0 then 1 else 0)

let () = main ()

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