Arg(3)								   OCaml library							    Arg(3)

NAME

       Arg - Parsing of command line arguments.

Module
       Module	Arg

Documentation
       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):

       - cmd -flag (a unit option)

       - cmd -int 1 (an int option with argument 1 )

       - cmd -string foobar (a string option with argument foobar )

       - cmd -float 12.34 (a float option with argument 12.34 )

       - cmd a b c (three anonymous arguments: a , b , and c )

       - cmd a b -- c d (two anonymous arguments and a rest option with two arguments)

       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  key-
       word,  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 to standard error an error message as follows:

       -  The reason for the error: unknown option, invalid or missing argument, etc.

       - usage_msg

       -   The list of options, each followed by the corresponding doc string.	Beware: options that have an empty doc string will not be included
       in the list.

       For the user to be able to specify anonymous arguments starting with a - , include for example ("-", String anon_fun, doc) in speclist .

       By default, parse recognizes two unit options, -help and --help , which will print to standard output 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 .  You must set it before calling parse_argv .  The initial value of 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 to standard error an error message that includes 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 usage_string : (key * spec * doc) list -> usage_msg -> string

       Returns the message that would have been printed by Arg.usage , if provided with the same parameters.

       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 aligned on the next
       line.

       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 ele-
       ment.

OCamldoc							    2014-06-09								    Arg(3)