Module Arg
: (moduleStdlib__Arg)typespec =
| Unit of(unit->unit)
(* Call the function with unit argument
*)
| Bool of(bool->unit)
(* Call the function with a bool argument
*)
| Set ofboolref
(* Set the reference to true
*)
| Clear ofboolref
(* Set the reference to false
*)
| String of(string->unit)
(* Call the function with a string argument
*)
| Set_string ofstringref
(* Set the reference to the string argument
*)
| Int of(int->unit)
(* Call the function with an int argument
*)
| Set_int ofintref
(* Set the reference to the int argument
*)
| Float of(float->unit)
(* Call the function with a float argument
*)
| Set_float offloatref
(* Set the reference to the float argument
*)
| Tuple ofspeclist
(* Take several arguments according to the spec list
*)
| Symbol ofstringlist*(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
*)
| Rest_all of(stringlist->unit)
(* Stop interpreting keywords and call the function with all remaining arguments
*)
| Expand of(string->stringarray)
(* If the remaining arguments to process are of the form ["-foo";"arg"]@rest where "foo" is
registered as Expandf , then the arguments f"arg"@rest are processed. Only allowed in
parse_and_expand_argv_dynamic .
*)
The concrete type describing the behavior associated with a keyword.
typekey = stringtypedoc = stringtypeusage_msg = stringtypeanon_fun = string->unitvalparse : (key*spec*doc)list->anon_fun->usage_msg->unitArg.parsespeclistanon_funusage_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 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 ("-",Stringanon_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 .
valparse_dynamic : (key*spec*doc)listref->anon_fun->usage_msg->unit
Same as Arg.parse , except that the speclist argument is a reference and may be updated during the
parsing. A typical use for this feature is to parse command lines of the form:
- command subcommand options where the list of options depends on the value of the subcommand
argument.
Since 4.01
valparse_argv : ?current:intref->stringarray->(key*spec*doc)list->anon_fun->usage_msg->unitArg.parse_argv~currentargsspeclistanon_funusage_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.
valparse_argv_dynamic : ?current:intref->stringarray->(key*spec*doc)listref->anon_fun->string->unit
Same as Arg.parse_argv , except that the speclist argument is a reference and may be updated during the
parsing. See Arg.parse_dynamic .
Since 4.01
valparse_and_expand_argv_dynamic : intref->stringarrayref->(key*spec*doc)listref->anon_fun->string->unit
Same as Arg.parse_argv_dynamic , except that the argv argument is a reference and may be updated during
the parsing of Expand arguments. See Arg.parse_argv_dynamic .
Since 4.05
valparse_expand : (key*spec*doc)list->anon_fun->usage_msg->unit
Same as Arg.parse , except that the Expand arguments are allowed and the Arg.current reference is not
updated.
Since 4.05
exceptionHelpofstring
Raised by Arg.parse_argv when the user asks for help.
exceptionBadofstring
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.
valusage : (key*spec*doc)list->usage_msg->unitArg.usagespeclistusage_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 .
valusage_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.
valalign : ?limit:int->(key*spec*doc)list->(key*spec*doc)list
Align the documentation strings by inserting spaces at the first alignment separator (tab or, if tab is
not found, space), according to the length of the keyword. Use a alignment separator 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.
valcurrent : intref
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.
valread_arg : string->stringarrayArg.read_argfile reads newline-terminated command line arguments from file file .
Since 4.05
valread_arg0 : string->stringarray
Identical to Arg.read_arg but assumes null character terminated command line arguments.
Since 4.05
valwrite_arg : string->stringarray->unitArg.write_argfileargs writes the arguments args newline-terminated into the file file . If any of the
arguments in args contains a newline, use Arg.write_arg0 instead.
Since 4.05
valwrite_arg0 : string->stringarray->unit
Identical to Arg.write_arg but uses the null character for terminator instead of newline.
Since 4.05
OCamldoc 2025-06-12 Stdlib.Arg(3o)
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