Module Cmdliner.Term

Terms.

A term is evaluated by a program to produce a result, which can be turned into an exit status. A term made of terms referring to command line arguments implicitly defines a command line syntax.

Terms

type +'a t

The type for terms evaluating to values of type 'a.

val const : 'a -> 'a t

const v is a term that evaluates to v.

val ($) : ('a -> 'b) t -> 'a t -> 'b t

f $ v is a term that evaluates to the result of applying the evaluation of v to the one of f.

val app : ('a -> 'b) t -> 'a t -> 'b t

app is ($).

Interacting with Cmdliner's evaluation

type 'a ret = [
| `Help of Manpage.format * string option
| `Error of bool * string
| `Ok of 'a
]

The type for command return values. See ret.

val ret : 'a ret t -> 'a t

ret v is a term whose evaluation depends on the case to which v evaluates. With :

  • `Ok v, it evaluates to v.
  • `Error (usage, e), the evaluation fails and Cmdliner prints the error e and the term's usage if usage is true.
  • `Help (format, name), the evaluation fails and Cmdliner prints the term's man page in the given format (or the man page for a specific name term in case of multiple term evaluation).
val term_result : ?⁠usage:bool -> ('a[ `Msg of string ]) Stdlib.result t -> 'a t

term_result ~usage t evaluates to

  • `Ok v if t evaluates to Ok v
  • `Error `Term with the error message e and usage shown according to usage (defaults to false), if t evaluates to Error (`Msg e).
val cli_parse_result : ('a[ `Msg of string ]) Stdlib.result t -> 'a t

cli_parse_result t is a term that evaluates to:

  • `Ok v if t evaluates to Ok v.
  • `Error `Parse with the error message e if t evaluates to Error (`Msg e).
val main_name : string t

main_name is a term that evaluates to the "main" term's name.

val choice_names : string list t

choice_names is a term that evaluates to the names of the terms to choose from.

val with_used_args : 'a t -> ('a * string list) t

with_used_args t is a term that evaluates to t tupled with the arguments from the command line that where used to evaluate t.

Term information

Term information defines the name and man page of a term. For simple evaluation this is the name of the program and its man page. For multiple term evaluation, this is the name of a command and its man page.

type exit_info

The type for exit status information.

val exit_info : ?⁠docs:string -> ?⁠doc:string -> ?⁠max:int -> int -> exit_info

exit_info ~docs ~doc min ~max describe the range of exit statuses from min to max (defaults to min). doc is the man page information for the statuses, defaults to "undocumented". docs is the title of the man page section in which the statuses will be listed, it defaults to Manpage.s_exit_status.

In doc the documentation markup language can be used with following variables:

  • $(status), the value of min.
  • $(status_max), the value of max.
  • The variables mentioned in info
val default_exits : exit_info list

default_exits is information for exit status exit_status_success added to default_error_exits.

val default_error_exits : exit_info list

default_error_exits is information for exit statuses exit_status_cli_error and exit_status_internal_error.

type env_info

The type for environment variable information.

val env_info : ?⁠docs:string -> ?⁠doc:string -> string -> env_info

env_info ~docs ~doc var describes an environment variable var. doc is the man page information of the environment variable, defaults to "undocumented". docs is the title of the man page section in which the environment variable will be listed, it defaults to Manpage.s_environment.

In doc the documentation markup language can be used with following variables:

  • $(env), the value of var.
  • The variables mentioned in info
type info

The type for term information.

val info : ?⁠man_xrefs:Manpage.xref list -> ?⁠man:Manpage.block list -> ?⁠envs:env_info list -> ?⁠exits:exit_info list -> ?⁠sdocs:string -> ?⁠docs:string -> ?⁠doc:string -> ?⁠version:string -> string -> info

info sdocs man docs doc version name is a term information such that:

  • name is the name of the program or the command.
  • version is the version string of the program, ignored for commands.
  • doc is a one line description of the program or command used for the NAME section of the term's man page. For commands this description is also used in the list of commands of the main term's man page.
  • docs, only for commands, the title of the section of the main term's man page where it should be listed (defaults to Manpage.s_commands).
  • sdocs defines the title of the section in which the standard --help and --version arguments are listed (defaults to Manpage.s_options).
  • exits is a list of exit statuses that the term evaluation may produce.
  • envs is a list of environment variables that influence the term's evaluation.
  • man is the text of the man page for the term.
  • man_xrefs are cross-references to other manual pages. These are used to generate a Manpage.s_see_also section.

doc, man, envs support the documentation markup language in which the following variables are recognized:

  • $(tname) the term's name.
  • $(mname) the main term's name.
val name : info -> string

name ti is the name of the term information.

Evaluation

type 'a result = [
| `Ok of 'a
| `Error of [ `Parse | `Term | `Exn ]
| `Version
| `Help
]

The type for evaluation results.

  • `Ok v, the term evaluated successfully and v is the result.
  • `Version, the version string of the main term was printed on the help formatter.
  • `Help, man page about the term was printed on the help formatter.
  • `Error `Parse, a command line parse error occurred and was reported on the error formatter.
  • `Error `Term, a term evaluation error occurred and was reported on the error formatter (see Term.ret).
  • `Error `Exn, an exception e was caught and reported on the error formatter (see the ~catch parameter of eval).
val eval : ?⁠help:Stdlib.Format.formatter -> ?⁠err:Stdlib.Format.formatter -> ?⁠catch:bool -> ?⁠env:(string -> string option) -> ?⁠argv:string array -> ('a t * info) -> 'a result

eval help err catch argv (t,i) is the evaluation result of t with command line arguments argv (defaults to Sys.argv).

If catch is true (default) uncaught exceptions are intercepted and their stack trace is written to the err formatter.

help is the formatter used to print help or version messages (defaults to Format.std_formatter). err is the formatter used to print error messages (defaults to Format.err_formatter).

env is used for environment variable lookup, the default uses Sys.getenv.

val eval_choice : ?⁠help:Stdlib.Format.formatter -> ?⁠err:Stdlib.Format.formatter -> ?⁠catch:bool -> ?⁠env:(string -> string option) -> ?⁠argv:string array -> ('a t * info) -> ('a t * info) list -> 'a result

eval_choice help err catch argv (t,i) choices is like eval except that if the first argument on the command line is not an option name it will look in choices for a term whose information has this name and evaluate it.

If the command name is unknown an error is reported. If the name is unspecified the "main" term t is evaluated. i defines the name and man page of the program.

val eval_peek_opts : ?⁠version_opt:bool -> ?⁠env:(string -> string option) -> ?⁠argv:string array -> 'a t -> 'a option * 'a result

eval_peek_opts version_opt argv t evaluates t, a term made of optional arguments only, with the command line argv (defaults to Sys.argv). In this evaluation, unknown optional arguments and positional arguments are ignored.

The evaluation returns a pair. The first component is the result of parsing the command line argv stripped from any help and version option if version_opt is true (defaults to false). It results in:

  • Some _ if the command line would be parsed correctly given the partial knowledge in t.
  • None if a parse error would occur on the options of t

The second component is the result of parsing the command line argv without stripping the help and version options. It indicates what the evaluation would result in on argv given the partial knowledge in t (for example it would return `Help if there's a help option in argv). However in contrasts to eval and eval_choice no side effects like error reporting or help output occurs.

Note. Positional arguments can't be peeked without the full specification of the command line: we can't tell apart a positional argument from the value of an unknown optional argument.

Turning evaluation results into exit codes

Note. If you are using the following functions to handle the evaluation result of a term you should add default_exits to the term's information ~exits argument.

WARNING. You should avoid status codes strictly greater than 125 as those may be used by some shells.

val exit_status_success : int

exit_status_success is 0, the exit status for success.

val exit_status_cli_error : int

exit_status_cli_error is 124, an exit status for command line parsing errors.

val exit_status_internal_error : int

exit_status_internal_error is 125, an exit status for unexpected internal errors.

val exit_status_of_result : ?⁠term_err:int -> 'a result -> int

exit_status_of_result ~term_err r is an exit(3) status code determined from r as follows:

val exit_status_of_status_result : ?⁠term_err:int -> int result -> int

exit_status_of_status_result is like exit_status_of_result except for `Ok n where n is used as the status exit code.

val exit : ?⁠term_err:int -> 'a result -> unit

exit ~term_err r is Stdlib.exit @@ exit_status_of_result ~term_err r

val exit_status : ?⁠term_err:int -> int result -> unit

exit_status ~term_err r is Stdlib.exit @@ exit_status_of_status_result ~term_err r