Module Flags

module Flags: sig .. end

exception Argument_missing of string

Raised by methods Flags.lookup.string and Flags.lookup.int when the requested argument isn't present.

class type lookup = object .. end

The argument parser Flags.go returns an object for querying its results.

val go : ?argv:string array -> ?usage:string -> string -> lookup

Flags.go spec parses the command-line arguments according to spec and returns a lookup object. If ?argv is given, it uses that rather than Sys.argv; if ?usage is given, it uses that as the sample command in the usage message.

The spec argument is a stylized sequence of arguments:

• "-a" and "--apple" specify boolean flags.
• "-a <N>" and "--apple <Color>" specify string arguments.
• "-a <N:int>" and "--apple <Color:int>" specify integer arguments.

Single-hyphen arguments consist of one alphabetic character, while long (double-hyphen) arguments start with an alphabetic character followed by an arbitrary number of alphanumerics.

For example, we might use "-q -v -b <Before:int> -a <After:int> --baz <Baz>" to specify a program that takes boolean flags "-q" and "-v", integer arguments "-b" and "-a", and a string argument "--baz". If we pass this string to Flags.go and it returns an object lookup, we may then query lookup, for example:

• lookup#bool "-q" checks whether "-q" was given.
• lookup#int "-b" returns an integer if "-b" was given, or raises Flags.Argument_missing otherwise.
• lookup#ints "-a" returns a list of integers (possibly 0 length) for each time "-a" was given.
• lookup#string ~default:"-" "--baz" returns the provided string if "--baz" was given, and "-" otherwise.