Module
Arg
:
sig end
Parsing of command line arguments.
This module provides a general mechanism for extracting options and arguments from the command line to the program.
Syntax of command lines: A keyword is a character string starting with a - An option is a keyword alone or followed by an argument. The types of keywords are: Unit , Bool , Set , Clear , String , Set_string , Int , Set_int , Float , Set_float , Tuple , Symbol , and Rest Unit , Set and Clear keywords take no argument. A Rest keyword takes the remaining of the command line as arguments. Every other keyword takes the following word on the command line as argument. Arguments not preceded by a keyword are called anonymous arguments.
Examples ( cmd is assumed to be the command name):.TP "" cmd -flag (a unit option)
type spec
=
| Unit
of
(unit -> unit)
(* Call the function with unit argument *)
| Bool
of
(bool -> unit)
(* Call the function with a bool argument *)
| Set
of
bool Pervasives.ref
(* Set the reference to true *)
| Clear
of
bool Pervasives.ref
(* Set the reference to false *)
| String
of
(string -> unit)
(* Call the function with a string argument *)
| Set_string
of
string Pervasives.ref
(* Set the reference to the string argument *)
| Int
of
(int -> unit)
(* Call the function with an int argument *)
| Set_int
of
int Pervasives.ref
(* Set the reference to the int argument *)
| Float
of
(float -> unit)
(* Call the function with a float argument *)
| Set_float
of
float Pervasives.ref
(* Set the reference to the float argument *)
| Tuple
of
spec list
(* Take several arguments according to the
spec list *)
| Symbol
of
string list * (string -> unit)
(* Take one of the symbols as argument and
call the function with the symbol *)
| Rest
of
(string -> unit)
(* Stop interpreting keywords and call the
function with each remaining argument *)
The concrete type describing the behavior associated with a keyword.
type key = string
type doc = string
type usage_msg = string
type anon_fun = string -> unit
val parse : (key * spec * doc) list -> anon_fun -> usage_msg -> unit
Arg.parse speclist anon_fun usage_msg parses the command line. speclist is a list of triples (key, spec, doc) key is the option keyword, it must start with a '-' character. spec gives the option type and the function to call when this option is found on the command line. doc is a one-line description of this option. anon_fun is called on anonymous arguments. The functions in spec and anon_fun are called in the same order as their arguments appear on the command line.
If an error occurs, Arg.parse exits the program, after printing an error message as follows:.TP "" The reason for the error: unknown option, invalid or missing argument, etc.
By default, parse recognizes two unit options, -help and --help , which will display usage_msg and the list of options, and exit the program. You can override this behaviour by specifying your own -help and --help options in speclist
val parse_argv : ?current:int Pervasives.ref -> string array -> (key * spec * doc) list -> anon_fun -> usage_msg -> unit
Arg.parse_argv ~current args speclist anon_fun usage_msg parses the array args as if it were the command line. It uses and updates the value of ~current (if given), or Arg.current it before calling parse_argv current is the index of the program name (argument 0) in the array. If an error occurs, Arg.parse_argv raises Arg.Bad with the error message as argument. If option -help or --help is given, Arg.parse_argv raises Arg.Help with the help message as argument.
exception Help of string
Raised by Arg.parse_argv when the user asks for help.
exception Bad of string
Functions in spec or anon_fun can raise Arg.Bad with an error message to reject invalid arguments. Arg.Bad is also raised by Arg.parse_argv in case of an error.
val usage : (key * spec * doc) list -> usage_msg -> unit
Arg.usage speclist usage_msg prints an error message including the list of valid options. This is the same message that Arg.parse prints in case of error. speclist and usage_msg are the same as for Arg.parse
val align : (key * spec * doc) list -> (key * spec * doc) list
Align the documentation strings by inserting spaces at the first space, according to the length of the keyword. Use a space as the first character in a doc string if you want to align the whole string. The doc strings corresponding to Symbol arguments are not aligned.
val current : int Pervasives.ref
Position (in Sys.argv ) of the argument being processed. You can change this value, e.g. to force Arg.parse to skip some arguments. Arg.parse uses the initial value of Arg.current as the index of argument 0 (the program name) and starts parsing arguments at the next element.