1Arg(3) OCaml library Arg(3)
2
6 Arg - Parsing of command line arguments.
7
9 Module Arg
10
12 Module Arg
13 : sig end
14 Parsing of command line arguments.
17 This module provides a general mechanism for extracting options and
19 arguments from the command line to the program.
20 Syntax of command lines: A keyword is a character string starting with
22 a - . An option is a keyword alone or followed by an argument. The
23 types of keywords are: Unit , Bool , Set , Clear , String , Set_string
24 , Int , Set_int , Float , Set_float , Tuple , Symbol , and Rest . Unit
25 , Set and Clear keywords take no argument. A Rest keyword takes the
26 remaining of the command line as arguments. Every other keyword takes
27 the following word on the command line as argument. Arguments not pre‐
28 ceded by a keyword are called anonymous arguments.
29 Examples ( cmd is assumed to be the command name):
31 - cmd -flag (a unit option)
33 - cmd -int 1 (an int option with argument 1 )
35 - cmd -string foobar (a string option with argument foobar )
37 - cmd -float 12.34 (a float option with argument 12.34 )
39 - cmd a b c (three anonymous arguments: a , b , and c )
41 - cmd a b -- c d (two anonymous arguments and a rest option with two
43 arguments)
44 type spec =
52 | Unit of (unit -> unit) (* Call the function with unit argument *)
53 | Bool of (bool -> unit) (* Call the function with a bool argument *)
54 | Set of bool Pervasives.ref (* Set the reference to true *)
55 | Clear of bool Pervasives.ref (* Set the reference to false *)
56 | String of (string -> unit) (* Call the function with a string argu‐
57 ment *)
58 | Set_string of string Pervasives.ref (* Set the reference to the
59 string argument *)
60 | Int of (int -> unit) (* Call the function with an int argument *)
61 | Set_int of int Pervasives.ref (* Set the reference to the int argu‐
62 ment *)
63 | Float of (float -> unit) (* Call the function with a float argument
64 *)
65 | Set_float of float Pervasives.ref (* Set the reference to the float
66 argument *)
67 | Tuple of spec list (* Take several arguments according to the spec
68 list *)
69 | Symbol of string list * (string -> unit) (* Take one of the symbols
70 as argument and call the function with the symbol *)
71 | Rest of (string -> unit) (* Stop interpreting keywords and call the
72 function with each remaining argument *)
73 The concrete type describing the behavior associated with a keyword.
76 type key = string
80 type doc = string
85 type usage_msg = string
90 type anon_fun = string -> unit
95 val parse : (key * spec * doc) list -> anon_fun -> usage_msg -> unit
101 Arg.parse speclist anon_fun usage_msg parses the command line.
104 speclist is a list of triples (key, spec, doc) . key is the option
105 keyword, it must start with a '-' character. spec gives the option
106 type and the function to call when this option is found on the command
107 line. doc is a one-line description of this option. anon_fun is
108 called on anonymous arguments. The functions in spec and anon_fun are
109 called in the same order as their arguments appear on the command line.
110 If an error occurs, Arg.parse exits the program, after printing an
112 error message as follows:
113 - The reason for the error: unknown option, invalid or missing argu‐
115 ment, etc.
116 - usage_msg
118 - The list of options, each followed by the corresponding doc string.
121 For the user to be able to specify anonymous arguments starting with a
123 - , include for example ("-", String anon_fun, doc) in speclist .
124 By default, parse recognizes two unit options, -help and --help , which
126 will display usage_msg and the list of options, and exit the program.
127 You can override this behaviour by specifying your own -help and --help
128 options in speclist .
129 val parse_argv : ?current:int Pervasives.ref -> string array -> (key *
134 spec * doc) list -> anon_fun -> usage_msg -> unit
135 Arg.parse_argv ~current args speclist anon_fun usage_msg parses the
138 array args as if it were the command line. It uses and updates the
139 value of ~current (if given), or Arg.current . You must set it before
140 calling parse_argv . The initial value of current is the index of the
141 program name (argument 0) in the array. If an error occurs,
142 Arg.parse_argv raises Arg.Bad with the error message as argument. If
143 option -help or --help is given, Arg.parse_argv raises Arg.Help with
144 the help message as argument.
145 exception Help of string
150 Raised by Arg.parse_argv when the user asks for help.
153 exception Bad of string
158 Functions in spec or anon_fun can raise Arg.Bad with an error message
161 to reject invalid arguments. Arg.Bad is also raised by Arg.parse_argv
162 in case of an error.
163 val usage : (key * spec * doc) list -> usage_msg -> unit
168 Arg.usage speclist usage_msg prints an error message including the list
171 of valid options. This is the same message that Arg.parse prints in
172 case of error. speclist and usage_msg are the same as for Arg.parse .
173 val align : (key * spec * doc) list -> (key * spec * doc) list
178 Align the documentation strings by inserting spaces at the first space,
180 according to the length of the keyword. Use a space as the first char‐
181 acter in a doc string if you want to align the whole string. The doc
182 strings corresponding to Symbol arguments are aligned on the next line.
183 val current : int Pervasives.ref
188 Position (in Sys.argv ) of the argument being processed. You can
190 change this value, e.g. to force Arg.parse to skip some arguments.
191 Arg.parse uses the initial value of Arg.current as the index of argu‐
192 ment 0 (the program name) and starts parsing arguments at the next ele‐
193 ment.
194OCamldoc 2017-03-22 Arg(3)