System.Console.CmdArgs.Explicit

This module constructs command lines. You may either use the helper functions (flagNone, flagOpt, mode etc.) or construct the type directly. These types are intended to give all the necessary power to the person constructing a command line parser.

For people constructing simpler command line parsers, the module System.Console.CmdArgs.Implicit may be more appropriate.

As an example of a parser:

 arguments :: Mode [(String,String)]
 arguments = mode "explicit" [] "Explicit sample program" (flagArg (upd "file") "FILE")
     [flagOpt "world" ["hello","h"] (upd "world") "WHO" "World argument"
     ,flagReq ["greeting","g"] (upd "greeting") "MSG" "Greeting to give"
     ,flagHelpSimple (("help",""):)]
     where upd msg x v = Right $ (msg,x):v

And this can be invoked by:

 main = do
     x <- processArgs arguments
     if ("help","") `elem` xs then
         print $ helpText def arguments
      else
         print x

Groups: The Group structure allows flags/modes to be grouped for the purpose of displaying help. When processing command lines, the group structure is ignored.

Modes: The Explicit module allows multiple mode programs by placing additional modes in modeGroupModes. Every mode is allowed sub-modes, and thus multiple levels of mode may be created. Given a mode x with sub-modes xs, if the first argument corresponds to the name of a sub-mode, then that sub-mode will be applied. If not, then the arguments will be processed by mode x. Consequently, if you wish to force the user to explicitly enter a mode, simply give sub-modes, and leave modeArgs as Nothing. Alternatively, if you want one sub-mode to be selected by default, place all it's flags both in the sub-mode and the outer mode.

Running command lines

process :: Mode a -> [String] -> Either String a

Process a list of flags (usually obtained from getArgs) with a mode. Returns Left and an error message if the command line fails to parse, or Right and the associated value.

processValue :: Mode a -> [String] -> a

Process a list of flags (usually obtained from getArgs) with a mode. Displays an error and exits with failure if the command line fails to parse, or returns the associated value. Implemeneted in terms of process.

processArgs :: Mode a -> IO a

Process the flags obtained by getArgs with a mode. Displays an error and exits with failure if the command line fails to parse, or returns the associated value. Implemented in terms of process.

Constructing command lines

type Name = String

A name, either the name of a flag (--foo) or the name of a mode.

type Help = String

A help message that goes with either a flag or a mode.

type FlagHelp = String

The type of a flag, i.e. --foo=TYPE.

parseBool :: String -> Maybe Bool

Parse a boolean, accepts as True: true yes on enabled 1.

data Group a

A group of items (modes or flags). The items are treated as a list, but the group structure is used when displaying the help message.

Constructors

Group

Fields

groupUnnamed :: [a]

Normal items.

groupHidden :: [a]

Items that are hidden (not displayed in the help message).

groupNamed :: [(Help, [a])]

Items that have been grouped, along with a description of each group.

Instances

Functor Group

Show a => Show (Group a)

Monoid (Group a)

fromGroup :: Group a -> [a]

Convert a group into a list.

toGroup :: [a] -> Group a

Convert a list into a group, placing all fields in groupUnnamed.

data Mode a

A mode. Each mode has three main features:

• A list of submodes (modeGroupModes)
• A list of flags (modeGroupFlags)
• Optionally an unnamed argument (modeArgs)

Constructors

Mode

Fields

modeGroupModes :: Group (Mode a)

The available sub-modes

modeNames :: [Name]

The names assigned to this mode (for the root mode, this name is used as the program name)

modeValue :: a

Value to start with

modeCheck :: a -> Either String a

modeHelp :: Help

Help text

modeHelpSuffix :: [String]

A longer help suffix displayed after a mode

modeArgs :: Maybe (Arg a)

An unnamed argument

modeGroupFlags :: Group (Flag a)

Groups of flags

Instances

Remap Mode

Show (Mode a)

modeModes :: Mode a -> [Mode a]

Extract the modes from a Mode

modeFlags :: Mode a -> [Flag a]

Extract the flags from a Mode

data FlagInfo

The FlagInfo type has the following meaning:

              FlagReq     FlagOpt      FlagOptRare/FlagNone
 -xfoo        -x=foo      -x=foo       -x= -foo
 -x foo       -x=foo      -x foo       -x= foo
 -x=foo       -x=foo      -x=foo       -x=foo
 --xx foo     --xx=foo    --xx foo     --xx foo
 --xx=foo     --xx=foo    --xx=foo     --xx=foo

Constructors

FlagReq

Required argument

FlagOpt String

Optional argument

FlagOptRare String

Optional argument that requires an = before the value

FlagNone

No argument

Instances

Eq FlagInfo

Ord FlagInfo

Show FlagInfo

fromFlagOpt :: FlagInfo -> String

Extract the value from inside a FlagOpt or FlagOptRare, or raises an error.

type Update a = String -> a -> Either String a

A function to take a string, and a value, and either produce an error message (Left), or a modified value (Right).

data Flag a

A flag, consisting of a list of flag names and other information.

Constructors

Flag

Fields

flagNames :: [Name]

The names for the flag.

flagInfo :: FlagInfo

Information about a flag's arguments.

flagValue :: Update a

The way of processing a flag.

flagType :: FlagHelp

The type of data for the flag argument, i.e. FILE/DIR/EXT

flagHelp :: Help

The help message associated with this flag.

Instances

Remap Flag

Show (Flag a)

data Arg a

An unnamed argument. Anything not starting with - is considered an argument, apart from "-" which is considered to be the argument "-", and any arguments following "--". For example:

 programname arg1 -j - --foo arg3 -- -arg4 --arg5=1 arg6

Would have the arguments:

 ["arg1","-","arg3","-arg4","--arg5=1","arg6"]

Constructors

Arg

Fields

argValue :: Update a

A way of processing the argument.

argType :: FlagHelp

The type of data for the argument, i.e. FILE/DIR/EXT

Instances

Remap Arg

Show (Arg a)

checkMode :: Mode a -> Maybe String

Check that a mode is well formed.

class Remap m where

Methods

remap

Arguments

:: (a -> b)

Embed a value

-> (b -> (a, a -> b))

Extract the mode and give a way of re-embedding

-> m a

-> m b

Instances

Remap Arg

Remap Flag

Remap Mode

remap2 :: Remap m => (a -> b) -> (b -> a) -> m a -> m b

mode :: Name -> a -> Help -> Arg a -> [Flag a] -> Mode a

Create a mode with a name, an initial value, some help text, a way of processing arguments and a list of flags.

modes :: String -> a -> Help -> [Mode a] -> Mode a

Create a list of modes, with a program name, an initial value, some help text and the child modes.

flagNone :: [Name] -> (a -> a) -> Help -> Flag a

Create a flag taking no argument value, with a list of flag names, an update function and some help text.

flagOpt :: String -> [Name] -> Update a -> FlagHelp -> Help -> Flag a

Create a flag taking an optional argument value, with an optional value, a list of flag names, an update function, the type of the argument and some help text.

flagReq :: [Name] -> Update a -> FlagHelp -> Help -> Flag a

Create a flag taking a required argument value, with a list of flag names, an update function, the type of the argument and some help text.

flagArg :: Update a -> FlagHelp -> Arg a

Create an argument flag, with an update function and the type of the argument.

flagBool :: [Name] -> (Bool -> a -> a) -> Help -> Flag a

Create a boolean flag, with a list of flag names, an update function and some help text.

flagHelpSimple :: (a -> a) -> Flag a

Create a help flag triggered by -?/--help.

flagHelpFormat :: (HelpFormat -> TextFormat -> a -> a) -> Flag a

Create a help flag triggered by -?/--help. The user may optionally modify help by specifying the format, such as:

 --help=all          - help for all modes
 --help=html         - help in HTML format
 --help=100          - wrap the text at 100 characters
 --help=100,one      - full text wrapped at 100 characters

flagVersion :: (a -> a) -> Flag a

Create a version flag triggered by -V/--version.

flagsVerbosity :: (Verbosity -> a -> a) -> [Flag a]

Create verbosity flags triggered by -v/--verbose and -q/--quiet

Displaying help

data HelpFormat

Specify the format to output the help.

Constructors

HelpFormatDefault

Equivalent to HelpFormatAll if there is not too much text, otherwise HelpFormatOne.

HelpFormatOne

Display only the first mode.

HelpFormatAll

Display all modes.

Instances

Bounded HelpFormat

Enum HelpFormat

Eq HelpFormat

Ord HelpFormat

Read HelpFormat

Show HelpFormat

Default HelpFormat

helpText :: HelpFormat -> Mode a -> [Text]

Generate a help message from a mode.