Command parameters
type 'a param = 'a Param.t
Specification of an individual parameter to the command's main function.
include Param.S with type 'a t := 'a Param.t
Command.Param
is intended to be used with the [%map_open]
syntax defined in ppx_let
, like so:
include Base.Applicative.S with type 'a t := 'a Param.t
val return : 'a -> 'a Param.t
module Applicative_infix : sig ... end
Various internal values
val help : 'a Param.t
The help text for the command.
val path : 'a Param.t
The subcommand path of the command.
val args : 'a Param.t
The arguments passed to the command.
val flag : ?aliases:Base.String.t Base.List.t -> ?full_flag_required:Base.Unit.t -> Base.String.t -> 'a Flag.t -> doc:Base.String.t -> 'a Param.t
flag name spec ~doc
specifies a command that, among other things, takes a flag named name
on its command line. doc
indicates the meaning of the flag.
All flags must have a dash at the beginning of the name. If name
is not prefixed by "-", it will be normalized to "-" ^ name
.
Unless full_flag_required
is used, one doesn't have to pass name
exactly on the command line, but only an unambiguous prefix of name
(i.e., a prefix which is not a prefix of any other flag's name).
NOTE: the doc
for a flag which takes an argument should be of the form arg_name ^ " " ^ description
where arg_name
describes the argument and description
describes the meaning of the flag.
NOTE: flag names (including aliases) containing underscores will be rejected. Use dashes instead.
NOTE: "-" by itself is an invalid flag name and will be rejected.
val flag_optional_with_default_doc : ?aliases:Base.String.t Base.List.t -> ?full_flag_required:Base.Unit.t -> Base.String.t -> 'a Arg_type.t -> ('a -> Sexp.t) -> default:'a -> doc:Base.String.t -> 'a Param.t
flag_optional_with_default_doc name arg_type sexp_of_default ~default ~doc
is a shortcut for flag
, where:
- The
Flag.t
isoptional_with_default default arg_type
- The
doc
is passed through with an explanation of what the default value appended.
anon spec
specifies a command that, among other things, takes the anonymous arguments specified by spec
.
module If_nothing_chosen : sig ... end
val choose_one : 'a Param.t Base.List.t -> if_nothing_chosen:('a, 'b) If_nothing_chosen.t -> 'a Param.t
choose_one clauses ~if_nothing_chosen
expresses a sum type. It raises if more than one of clauses
is Some _
. When if_nothing_chosen = `Raise
, it also raises if none of clauses
is Some _
.
and_arg_names t
returns both the value of t
and the names of the arguments that went into t
. Useful for errors that reference multiple params.
val const : 'a -> 'a Param.t
Superceded by return
, preserved for backwards compatibility.
Superceded by both
, preserved for backwards compatibility.
Command specifications
Composable command-line specifications.
Ultimately one forms a basic command by combining a spec of type ('main, unit ->
unit) t
with a main function of type 'main
; see the basic
function below. Combinators in this library incrementally build up the type of main according to what command-line parameters it expects, so the resulting type of main
is something like:
arg1 -> ... -> argN -> unit -> unit
It may help to think of ('a, 'b) t
as a function space 'a -> 'b
embellished with information about:
- how to parse the command line
- what the command does and how to call it
- how to autocomplete a partial command line
One can view a value of type ('main_in, 'main_out) t
as a function that transforms a main function from type 'main_in
to 'main_out
, typically by supplying some arguments. E.g., a value of type Spec.t
might have type:
(arg1 -> ... -> argN -> 'r, 'r) Spec.t
Such a value can transform a main function of type arg1 -> ... -> argN -> 'r
by supplying it argument values of type arg1
, ..., argn
, leaving a main function whose type is 'r
. In the end, Command.basic
takes a completed spec where 'r = unit -> unit
, and hence whose type looks like:
(arg1 -> ... -> argN -> unit -> unit, unit -> unit) Spec.t
A value of this type can fully apply a main function of type arg1 -> ... -> argN ->
unit -> unit
to all its arguments.
The final unit argument allows the implementation to distinguish between the phases of (1) parsing the command line and (2) running the body of the command. Exceptions raised in phase (1) lead to a help message being displayed alongside the exception. Exceptions raised in phase (2) are displayed without any command line help.
The view of ('main_in, main_out) Spec.t
as a function from 'main_in
to 'main_out
is directly reflected by the step
function, whose type is:
val step : ('m1 -> 'm2) -> ('m1, 'm2) t
val empty : ('m, 'm) t
The empty command-line spec.
Adds a rightmost parameter onto the type of main.
Adds a leftmost parameter onto the type of main.
This function should only be used as a workaround in situations where the order of composition is at odds with the order of anonymous arguments because you're factoring out some common spec.
val step : ('m1 -> 'm2) -> ('m1, 'm2) t
Combinator for patching up how parameters are obtained or presented.
Here are a couple examples of some of its many uses:
introducing labeled arguments
step (fun m v -> m ~foo:v) +> flag "-foo" no_arg : (foo:bool -> 'm, 'm) t
prompting for missing values
step (fun m user -> match user with | Some user -> m user | None -> print_string "enter username: "; m (read_line ())) +> flag "-user" (optional string) ~doc:"USER to frobnicate" : (string -> 'm, 'm) t
A use of step
might look something like:
step (fun main -> let ... in main x1 ... xN) : (arg1 -> ... -> argN -> 'r, 'r) t
Thus, step
allows one to write arbitrary code to decide how to transform a main function. As a simple example:
step (fun main -> main 13.) : (float -> 'r, 'r) t
This spec is identical to const 13.
; it transforms a main function by supplying it with a single float argument, 13.
. As another example:
step (fun m v -> m ~foo:v) : (foo:'foo -> 'r, 'foo -> 'r) t
This spec transforms a main function that requires a labeled argument into a main function that requires the argument unlabeled, making it easily composable with other spec combinators.
Combinator for defining a class of commands with common behavior.
Here are two examples of command classes defined using wrap
:
print top-level exceptions to stderr
wrap (fun ~run ~main -> Exn.handle_uncaught ~exit:true (fun () -> run main) ) : ('m, unit) t -> ('m, unit) t
iterate over lines from stdin
wrap (fun ~run ~main -> In_channel.iter_lines stdin ~f:(fun line -> run (main line)) ) : ('m, unit) t -> (string -> 'm, unit) t
module Arg_type : module type of Arg_type with type 'a t = 'a Arg_type.t
include module type of Arg_type.Export
val string : Base.String.t Arg_type.t
val int : Base.Int.t Arg_type.t
Beware that an anonymous argument of type int
cannot be specified as negative, as it is ambiguous whether -1 is a negative number or a flag. (The same applies to float
, time_span
, etc.) You can use the special built-in "-anon" flag to force a string starting with a hyphen to be interpreted as an anonymous argument rather than as a flag, or you can just make it a parameter to a flag to avoid the issue.
val char : Base.Char.t Arg_type.t
val float : Base.Float.t Arg_type.t
val bool : Base.Bool.t Arg_type.t
val date : Date.t Arg_type.t
val percent : Percent.t Arg_type.t
val host_and_port : Host_and_port.t Arg_type.t
val sexp : Sexp.t Arg_type.t
val sexp_conv : (Sexp.t -> 'a) -> 'a Arg_type.t
type 'a flag = 'a Flag.t
A flag specification.
include module type of Flag with type 'a t := 'a flag
val required : 'a Arg_type.t -> 'a flag
Required flags must be passed exactly once.
val optional : 'a Arg_type.t -> 'a flag
Optional flags may be passed at most once.
val optional_with_default : 'a -> 'a Arg_type.t -> 'a flag
optional_with_default
flags may be passed at most once, and default to a given value.
val listed : 'a Arg_type.t -> 'a flag
listed
flags may be passed zero or more times.
val one_or_more : 'a Arg_type.t -> 'a flag
one_or_more
flags must be passed one or more times.
val no_arg : 'a flag
no_arg
flags may be passed at most once. The boolean returned is true iff the flag is passed on the command line.
val no_arg_register : key:'a Univ_map.With_default.Key.t -> value:'a -> 'a flag
no_arg_register ~key ~value
is like no_arg
, but associates value
with key
in the autocomplete environment.
val no_arg_some : 'a -> 'a flag
no_arg_some value
is like no_arg
, but will return Some value
if the flag is passed on the command line, and return None
otherwise.
val no_arg_abort : exit:(Base.Unit.t -> Nothing.t) -> 'a flag
no_arg_abort ~exit
is like no_arg
, but aborts command-line parsing by calling exit
. This flag type is useful for "help"-style flags that just print something and exit.
val escape : 'a flag
escape
flags may be passed at most once. They cause the command line parser to abort and pass through all remaining command line arguments as the value of the flag.
A standard choice of flag name to use with escape
is "--"
.
val flags_of_args_exn : Arg.t Base.List.t -> ('a, 'a) t
flags_of_args_exn args
creates a spec from Caml.Arg.t
s, for compatibility with OCaml's base libraries. Fails if it encounters an arg that cannot be converted.
NOTE: There is a difference in side effect ordering between Caml.Arg
and Command
. In the Arg
module, flag handling functions embedded in Caml.Arg.t
values will be run in the order that flags are passed on the command line. In the Command
module, using flags_of_args_exn flags
, they are evaluated in the order that the Caml.Arg.t
values appear in args
.
type 'a anons = 'a Anons.t
A specification of some number of anonymous arguments.
include module type of Anons with type 'a t := 'a anons
val (%:) : Base.String.t -> 'a Arg_type.t -> 'a anons
(name %: typ)
specifies a required anonymous argument of type typ
.
The name
must not be surrounded by whitespace; if it is, an exn will be raised.
If the name
is surrounded by a special character pair (<>, {}, [] or (),) name
will remain as-is, otherwise, name
will be uppercased.
In the situation where name
is only prefixed or only suffixed by one of the special character pairs, or different pairs are used (e.g., "<ARG]"), an exn will be raised.
The (possibly transformed) name
is mentioned in the generated help for the command.
sequence anons
specifies a sequence of anonymous arguments. An exception will be raised if anons
matches anything other than a fixed number of anonymous arguments.
non_empty_sequence_as_pair anons
and non_empty_sequence_as_list anons
are like sequence anons
except that an exception will be raised if there is not at least one anonymous argument given.
(maybe_with_default default anons)
indicates an optional anonymous argument with a default value.