System.Console.CmdArgs.GetOpt

This provides a compatiblity wrapper to the System.Console.GetOpt module in base. That module is essentially a Haskell port of the GNU getopt library.

Changes: The changes from GetOpt are listed in the documentation for each function.

Documentation

convert :: String -> [OptDescr a] -> Mode ([a], [String])

Given a help text and a list of option descriptions, generate a Mode.

getOpt :: ArgOrder a -> [OptDescr a] -> [String] -> ([a], [String], [String])

Process the command-line, and return the list of values that matched (and those that didn't). The arguments are:

• The order requirements (see ArgOrder)
• The option descriptions (see OptDescr)
• The actual command line arguments (presumably got from getArgs).

getOpt returns a triple consisting of the option arguments, a list of non-options, and a list of error messages.

Changes: The list of errors will contain at most one entry, and if an error is present then the other two lists will be empty.

getOpt' :: ArgOrder a -> [OptDescr a] -> [String] -> ([a], [String], [String], [String])

Changes: This is exactly the same as getOpt, but the 3rd element of the tuple (second last) will be an empty list.

usageInfo :: String -> [OptDescr a] -> String

Return a string describing the usage of a command, derived from the header (first argument) and the options described by the second argument.

data ArgOrder a

What to do with options following non-options.

Changes: Only Permute is allowed, both RequireOrder and ReturnInOrder have been removed.

Constructors

Permute

data OptDescr a

Each OptDescr describes a single option/flag.

The arguments to Option are:

• list of short option characters
• list of long option strings (without "--", may not be 1 character long)
• argument descriptor
• explanation of option for userdata

Constructors

Option [Char] [String] (ArgDescr a) String

data ArgDescr a

Describes whether an option takes an argument or not, and if so how the argument is injected into a value of type a.

Constructors

NoArg a

no argument expected

ReqArg (String -> a) String

option requires argument

OptArg (Maybe String -> a) String

optional argument