Safe Haskell | Safe-Inferred |
---|
The options
package lets library and application developers easily work
with command-line options.
The following example is a full program that can accept two options,
--message
and --quiet
:
import Control.Applicative import Options data MainOptions = MainOptions { optMessage :: String , optQuiet :: Bool } instanceOptions
MainOptions wheredefineOptions
= pure MainOptions <*>simpleOption
"message" "Hello world!" "A message to show the user." <*>simpleOption
"quiet" False "Whether to be quiet." main :: IO () main =runCommand
$ \opts args -> do if optQuiet opts then return () else putStrLn (optMessage opts)
$ ./hello Hello world! $ ./hello --message='ciao mondo' ciao mondo $ ./hello --quiet $
In addition, this library will automatically create documentation options
such as --help
and --help-all
:
$ ./hello --help Help Options: -h, --help Show option summary. --help-all Show all help options. Application Options: --message :: text A message to show the user. default: "Hello world!" --quiet :: bool Whether to be quiet. default: false
- class Options opts where
- defineOptions :: DefineOptions opts
- defaultOptions :: Options opts => opts
- simpleOption :: SimpleOptionType a => String -> a -> String -> DefineOptions a
- data DefineOptions a
- class SimpleOptionType a where
- data Subcommand cmdOpts action
- subcommand :: (Options cmdOpts, Options subcmdOpts) => String -> (cmdOpts -> subcmdOpts -> [String] -> action) -> Subcommand cmdOpts action
- runCommand :: (MonadIO m, Options opts) => (opts -> [String] -> m a) -> m a
- runSubcommand :: (Options opts, MonadIO m) => [Subcommand opts (m a)] -> m a
- class Parsed a
- parsedError :: Parsed a => a -> Maybe String
- parsedHelp :: Parsed a => a -> String
- data ParsedOptions opts
- parsedOptions :: ParsedOptions opts -> Maybe opts
- parsedArguments :: ParsedOptions opts -> [String]
- parseOptions :: Options opts => [String] -> ParsedOptions opts
- data ParsedSubcommand action
- parsedSubcommand :: ParsedSubcommand action -> Maybe action
- parseSubcommand :: Options cmdOpts => [Subcommand cmdOpts action] -> [String] -> ParsedSubcommand action
- data OptionType val
- defineOption :: OptionType a -> (Option a -> Option a) -> DefineOptions a
- data Option a
- optionShortFlags :: Option a -> [Char]
- optionLongFlags :: Option a -> [String]
- optionDefault :: Option a -> a
- optionDescription :: Option a -> String
- optionGroup :: Option a -> Maybe Group
- data Group
- group :: String -> String -> String -> Group
- groupName :: Group -> String
- groupTitle :: Group -> String
- groupDescription :: Group -> String
- optionType_bool :: OptionType Bool
- optionType_string :: OptionType String
- optionType_int :: OptionType Int
- optionType_int8 :: OptionType Int8
- optionType_int16 :: OptionType Int16
- optionType_int32 :: OptionType Int32
- optionType_int64 :: OptionType Int64
- optionType_word :: OptionType Word
- optionType_word8 :: OptionType Word8
- optionType_word16 :: OptionType Word16
- optionType_word32 :: OptionType Word32
- optionType_word64 :: OptionType Word64
- optionType_integer :: OptionType Integer
- optionType_float :: OptionType Float
- optionType_double :: OptionType Double
- optionType_maybe :: OptionType a -> OptionType (Maybe a)
- optionType_list :: Char -> OptionType a -> OptionType [a]
- optionType_set :: Ord a => Char -> OptionType a -> OptionType (Set a)
- optionType_map :: Ord k => Char -> Char -> OptionType k -> OptionType v -> OptionType (Map k v)
- optionType_enum :: (Bounded a, Enum a, Show a) => String -> OptionType a
- optionType :: String -> val -> (String -> Either String val) -> (val -> String) -> OptionType val
- optionTypeName :: OptionType val -> String
- optionTypeDefault :: OptionType val -> val
- optionTypeParse :: OptionType val -> String -> Either String val
- optionTypeShow :: OptionType val -> val -> String
- optionTypeUnary :: OptionType val -> Maybe val
- optionTypeMerge :: OptionType val -> Maybe ([val] -> val)
Defining options
class Options opts whereSource
Options are defined together in a single data type, which will be an
instance of Options
.
See defineOptions
for details on defining instances of Options
.
defineOptions :: DefineOptions optsSource
Defines the structure and metadata of the options in this type, including their types, flag names, and documentation.
Options with a basic type and a single flag name may be defined
with simpleOption
. Options with more complex requirements may
be defined with defineOption
.
Non-option fields in the type may be set using applicative functions
such as pure
.
Options may be included from another type by using a nested call to
defineOptions
.
Library authors are encouraged to aggregate their options into a few top-level types, so application authors can include it easily in their own option definitions.
defaultOptions :: Options opts => optsSource
An options value containing only the default values for each option. This is equivalent to the options value when parsing an empty argument list.
simpleOption :: SimpleOptionType a => String -> a -> String -> DefineOptions aSource
Defines a new option in the current options type.
class SimpleOptionType a whereSource
Defining subcommands
data Subcommand cmdOpts action Source
:: (Options cmdOpts, Options subcmdOpts) | |
=> String | The subcommand name. |
-> (cmdOpts -> subcmdOpts -> [String] -> action) | The action to run. |
-> Subcommand cmdOpts action |
Running main with options
runCommand :: (MonadIO m, Options opts) => (opts -> [String] -> m a) -> m aSource
Retrieve getArgs
, and attempt to parse it into a
valid value of an Options
type plus a list of left-over arguments. The
options and arguments are then passed to the provided computation.
If parsing fails, this computation will print an error and call
exitFailure
.
If parsing succeeds, and the user has passed a --help
flag, and the
developer is using the default help flag definitions, then this computation
will print documentation and call exitSuccess
.
See runSubcommand
for details on subcommand support.
runSubcommand :: (Options opts, MonadIO m) => [Subcommand opts (m a)] -> m aSource
Used to run applications that are split into subcommands.
Use subcommand
to define available commands and their actions, then pass
them to this computation to select one and run it. If the user specifies
an invalid subcommand, this computation will print an error and call
exitFailure
. In handling of invalid flags or --help
, runSubcommand
acts like runCommand
.
import Control.Applicative import Control.Monad (unless) import Options data MainOptions = MainOptions { optQuiet :: Bool } instanceOptions
MainOptions wheredefineOptions
= pure MainOptions <*>simpleOption
"quiet" False "Whether to be quiet." data HelloOpts = HelloOpts { optHello :: String } instanceOptions
HelloOpts wheredefineOptions
= pure HelloOpts <*>simpleOption
"hello" "Hello!" "How to say hello." data ByeOpts = ByeOpts { optName :: String } instanceOptions
ByeOpts wheredefineOptions
= pure ByeOpts <*>simpleOption
"name" "" "The user's name." hello :: MainOptions -> HelloOpts -> [String] -> IO () hello mainOpts opts args = unless (optQuiet mainOpts) $ do putStrLn (optHello opts) bye :: MainOptions -> ByeOpts -> [String] -> IO () bye mainOpts opts args = unless (optQuiet mainOpts) $ do putStrLn ("Good bye " ++ optName opts) main :: IO () main =runSubcommand
[subcommand
"hello" hello ,subcommand
"bye" bye ]
$ ./app hello Hello! $ ./app hello --hello='Allo!' Allo! $ ./app bye Good bye $ ./app bye --name='Alice' Good bye Alice
Parsing argument lists
See
and parseOptions
.
parseSubcommand
Parsed (ParsedSubcommand a) | |
Parsed (ParsedOptions a) |
parsedError :: Parsed a => a -> Maybe StringSource
Get the error that prevented options from being parsed from argv,
or Nothing
if no error was detected.
parsedHelp :: Parsed a => a -> StringSource
Get a help message to show the user. If the arguments included
a help flag, this will be a message appropriate to that flag.
Otherwise, it is a summary (equivalent to --help
).
This is always a non-empty string, regardless of whether the parse succeeded or failed. If you need to perform additional validation on the options value, this message can be displayed if validation fails.
Parsing options
parsedOptions :: ParsedOptions opts -> Maybe optsSource
Get the options value that was parsed from argv, or Nothing
if the
arguments could not be converted into options.
Note: This function return Nothing
if the user provided a help flag. To
check whether an error occured during parsing, check the value of
.
parsedError
parsedArguments :: ParsedOptions opts -> [String]Source
Get command-line arguments remaining after parsing options. The arguments are unchanged from the original argument list, and have not been decoded or otherwise transformed.
parseOptions :: Options opts => [String] -> ParsedOptions optsSource
Attempt to convert a list of command-line arguments into an options value. This can be used by application developers who want finer control over error handling, or who want to perform additional validation on the options value.
The argument list must be in the same encoding as the result of
getArgs
.
Use
, parsedOptions
, parsedArguments
, and
parsedError
to inspect the result of parsedHelp
.
parseOptions
Example:
getOptionsOrDie :: Options a => IO a getOptionsOrDie = do argv <- System.Environment.getArgs let parsed =parseOptions
argv caseparsedOptions
parsed of Just opts -> return opts Nothing -> caseparsedError
parsed of Just err -> do hPutStrLn stderr (parsedHelp
parsed) hPutStrLn stderr err exitFailure Nothing -> do hPutStr stdout (parsedHelp
parsed) exitSuccess
Parsing sub-commands
parsedSubcommand :: ParsedSubcommand action -> Maybe actionSource
Get the subcommand action that was parsed from argv, or Nothing
if the
arguments could not be converted into a valid action.
Note: This function return Nothing
if the user provided a help flag. To
check whether an error occured during parsing, check the value of
.
parsedError
parseSubcommand :: Options cmdOpts => [Subcommand cmdOpts action] -> [String] -> ParsedSubcommand actionSource
Attempt to convert a list of command-line arguments into a subcommand action. This can be used by application developers who want finer control over error handling, or who want subcommands that run in an unusual monad.
The argument list must be in the same encoding as the result of
getArgs
.
Use
, parsedSubcommand
, and parsedError
to inspect the
result of parsedHelp
.
parseSubcommand
Example:
runSubcommand :: Options cmdOpts => [Subcommand cmdOpts (IO a)] -> IO a runSubcommand subcommands = do argv <- System.Environment.getArgs let parsed =parseSubcommand
subcommands argv caseparsedSubcommand
parsed of Just cmd -> cmd Nothing -> caseparsedError
parsed of Just err -> do hPutStrLn stderr (parsedHelp
parsed) hPutStrLn stderr err exitFailure Nothing -> do hPutStr stdout (parsedHelp
parsed) exitSuccess
Advanced option definitions
data OptionType val Source
An option's type determines how the option will be parsed, and which Haskell type the parsed value will be stored as. There are many types available, covering most basic types and a few more advanced types.
defineOption :: OptionType a -> (Option a -> Option a) -> DefineOptions aSource
Defines a new option in the current options type.
All options must have one or more flags. Options may also have a default value, a description, and a group.
The flags are how the user specifies an option on the command line. Flags
may be short or long. See optionShortFlags
and optionLongFlags
for
details.
defineOption
optionType_word16
(\o -> o {optionLongFlags
= ["port"] ,optionDefault
= 80 })
optionShortFlags :: Option a -> [Char]Source
Short flags are a single character. When entered by a user, they are preceded by a dash and possibly other short flags.
Short flags must be a letter or a number.
Example: An option with optionShortFlags = ['p']
may be set using:
$ ./app -p 443 $ ./app -p443
optionLongFlags :: Option a -> [String]Source
Long flags are multiple characters. When entered by a user, they are preceded by two dashes.
Long flags may contain letters, numbers, '-'
, and '_'
.
Example: An option with optionLongFlags = ["port"]
may be set using:
$ ./app --port 443 $ ./app --port=443
optionDefault :: Option a -> aSource
Options may have a default value. This will be parsed as if the user had entered it on the command line.
optionDescription :: Option a -> StringSource
An option's description is used with the default implementation
of --help
. It should be a short string describing what the option
does.
optionGroup :: Option a -> Maybe GroupSource
Which group the option is in. See the "Option groups" section for details.
Option groups
:: String | Name |
-> String | Title; see |
-> String | Description; see |
-> Group |
Define an option group with the given name and title. Use
groupDescription
to add additional descriptive text, if needed.
groupTitle :: Group -> StringSource
A short title for the group, which is used when printing
--help
output.
groupDescription :: Group -> StringSource
A description of the group, which is used when printing
--help
output.
Option types
optionType_bool :: OptionType BoolSource
Store an option as a
. The option's value must be either
Bool
"true"
or "false"
.
Boolean options are unary, which means that their value is optional when specified on the command line. If a flag is present, the option is set to True.
$ ./app -q $ ./app --quiet
Boolean options may still be specified explicitly by using long flags with
the --flag=value
format. This is the only way to set a unary flag to
"false"
.
$ ./app --quiet=true $ ./app --quiet=false
optionType_string :: OptionType StringSource
Store an option value as a
. The value is decoded to Unicode
first, if needed. The value may contain non-Unicode bytes, in which case
they will be stored using GHC 7.4's encoding for mixed-use strings.
String
optionType_integer :: OptionType IntegerSource
Store an option as an
. The option value must be an integer.
There is no minimum or maximum value.
Integer
optionType_maybe :: OptionType a -> OptionType (Maybe a)Source
Store an option as a
of another type. The value will be
Maybe
Nothing
if the option is set to an empty string.
:: Char | Element separator |
-> OptionType a | Element type |
-> OptionType [a] |
Store an option as a list, using another option type for the elements. The separator should be a character that will not occur within the values, such as a comma or semicolon.
:: Ord a | |
=> Char | Element separator |
-> OptionType a | Element type |
-> OptionType (Set a) |
Store an option as a
, using another option type for the
elements. The separator should be a character that will not occur within
the values, such as a comma or semicolon.
Set
Duplicate elements in the input are permitted.
:: Ord k | |
=> Char | Item separator |
-> Char | Key/Value separator |
-> OptionType k | Key type |
-> OptionType v | Value type |
-> OptionType (Map k v) |
Store an option as a Map
, using other option types for the keys and
values.
The item separator is used to separate key/value pairs from eachother. It should be a character that will not occur within either the keys or values.
The value separator is used to separate the key from the value. It should be a character that will not occur within the keys. It may occur within the values.
Duplicate keys in the input are permitted. The final value for each key is stored.
:: (Bounded a, Enum a, Show a) | |
=> String | Option type name |
-> OptionType a |
Store an option as one of a set of possible values. The type must be a
bounded enumeration, and the type's Show
instance will be used to
implement the parser.
This is a simplistic implementation, useful for quick scripts. Users with
more complex requirements for enum parsing are encouraged to define their
own option types using optionType
.
data Action = Hello | Goodbye deriving (Bounded, Enum, Show) data MainOptions = MainOptions { optAction :: Action } instanceOptions
MainOptions wheredefineOptions
= pure MainOptions <*>defineOption
(optionType_enum "action") (\o -> o {optionLongFlags
= ["action"] ,optionDefault
= Hello }) main =runCommand
$ \opts args -> do putStrLn ("Running action " ++ show (optAction opts))
$ ./app Running action Hello $ ./app --action=Goodbye Running action Goodbye
Custom option types
:: String | Name |
-> val | Default value |
-> (String -> Either String val) | Parser |
-> (val -> String) | Formatter |
-> OptionType val |
Define a new option type with the given name, default, and behavior.
optionTypeName :: OptionType val -> StringSource
The name of this option type; used in --help
output.
optionTypeDefault :: OptionType val -> valSource
The default value for options of this type. This will be used
if optionDefault
is not set when defining the option.
optionTypeParse :: OptionType val -> String -> Either String valSource
Try to parse the given string to an option value. If parsing fails, an error message will be returned.
optionTypeShow :: OptionType val -> val -> StringSource
Format the value for display; used in --help
output.
optionTypeUnary :: OptionType val -> Maybe valSource
If not Nothing, then options of this type may be set by a unary flag. The option will be parsed as if the given value were set.
optionTypeMerge :: OptionType val -> Maybe ([val] -> val)Source
If not Nothing, then options of this type may be set with repeated
flags. Each flag will be parsed with optionTypeParse
, and the
resulting parsed values will be passed to this function for merger
into the final value.