Copyright	(c) 2007 Bart Massey
License	BSD-style (see the file COPYING)
Maintainer	Bart Massey <bart.massey@gmail.com>
Stability	stable
Portability	portable
Safe Haskell	Safe
Language	Haskell98

System.Console.ParseArgs

Contents

Describing allowed arguments
- DataArg and its pseudo-constructors
Argument processing
- Getting parse results
- Using parse results
Misc

Description

ParseArgs is a full-featured command-line argument parsing library.

This module supplies an argument parser. Given a description of type [Arg] of the legal arguments to the program, a list of argument strings, and a bit of extra information, the parseArgs function in this module returns an Args data structure suitable for querying using the provided functions gotArg, getArg, etc.

Synopsis

Describing allowed arguments

The argument parser requires a description of the arguments that will be parsed. This is supplied as a list of Arg records, built up using the functions described here.

data Ord a => Arg a Source

The description of an argument, suitable for messages and for parsing. The argData field is used both for flags with a data argument, and for positional data arguments.

There are two cases:

The argument is a flag, in which case at least one of argAbbr and argName is provided;
The argument is positional, in which case neither argAbbr nor argName are provided, but argData is.

If none of argAbbr, argName, or argData are provided, this is an error. See also the argDataRequired, argDataOptional, and argDataDefaulted functions below, which are used to generate argData.

Constructors

Arg
Fields argIndex :: a Connects the input description to the output argument. argAbbr :: Maybe Char One-character flag name. argName :: Maybe String "Long name" of flag. argData :: Maybe DataArg Datum description. argDesc :: String Documentation for the argument.

data Argtype Source

The types of an argument carrying data. The constructor argument is used to carry a default value.

The constructor argument should really be hidden. Values of this type are normally constructed within the pseudo-constructors pseudo-constructors argDataRequired, argDataOptional, and argDataDefaulted, to which only the constructor function itself is passed.

Constructors

ArgtypeString (Maybe String)
ArgtypeInteger (Maybe Integer)
ArgtypeInt (Maybe Int)
ArgtypeDouble (Maybe Double)
ArgtypeFloat (Maybe Float)

data ArgsComplete Source

How "sloppy" the parse is.

Constructors

ArgsComplete	Any extraneous arguments (unparseable from description) will cause the parser to fail.
ArgsTrailing String	Trailing extraneous arguments are permitted, and will be skipped, saved, and returned. The constructor argument is the name of the args.
ArgsInterspersed	All extraneous arguments are permitted, and will be skipped, saved, and returned.

Instances

APCData ArgsComplete Source

data ArgsDash Source

Whether to always treat an unknown argument beginning with "-" as an error, or to allow it to be used as a positional argument when possible.

Constructors

ArgsHardDash	If an argument begins with a "-", it will always be treated as an error unless it corresponds to a flag description.
ArgsSoftDash	If an argument beginning with a "-" is unrecognized as a flag, treat it as a positional argument if possible. Otherwise it is an error.

Instances

Eq ArgsDash Source

class APCData a where Source

Class for building parse control information, for backward compatibility.

Methods

getAPCData Source

Arguments

:: a
-> ArgsParseControl	Build an `ArgsParseControl` structure from the given info.

Instances

APCData ArgsParseControl Source
APCData ArgsComplete Source

data ArgsParseControl Source

Record containing the collective parse control information.

Constructors

ArgsParseControl
Fields apcComplete :: ArgsComplete Level of completeness of parse. apcDash :: ArgsDash Handling of dashes in parse.

Instances

APCData ArgsParseControl Source

DataArg and its pseudo-constructors

data DataArg Source

Information specific to an argument carrying a datum. This is an opaque type, whose instances are constructed using the pseudo-constructors argDataRequired, argDataOptional, and argDataDefaulted.

argDataRequired Source

Arguments

:: String	Datum print name.
-> (Maybe a -> Argtype)	Type constructor for datum.
-> Maybe DataArg	Result is `argData`-ready.

Generate the argData for the given non-optional argument.

argDataOptional Source

Arguments

:: String	Datum print name.
-> (Maybe a -> Argtype)	Type constructor for datum.
-> Maybe DataArg	Result is `argData`-ready.

Generate the argData for the given optional argument with no default.

argDataDefaulted Source

Arguments

:: String	Datum print name.
-> (Maybe a -> Argtype)	Type constructor for datum.
-> a	Datum default value.
-> Maybe DataArg	Result is `argData`-ready.

Generate the argData for the given optional argument with the given default.

Argument processing

The argument descriptions are used to parse the command line arguments, and the results of the parse can later be (efficiently) queried to determine program behavior.

Getting parse results

The argument parser returns an opaque map from argument index to parsed argument data (plus some convenience information).

data Ord a => Args a Source

The data structure parseArgs produces. There is a should-be-hidden field that describes the parse.

Constructors

Args
Fields __args :: ArgRecord a The argument parse, only listed here to work around a Haddock bug. See https://github.com/haskell/haddock/issues/456. argsProgName :: String Basename of 0th argument. argsUsage :: String Full usage string. argsRest :: [String] Remaining unprocessed arguments.

parseArgs Source

Arguments

:: (Show a, Ord a, APCData b)
=> b	Configuration for parse.
-> [Arg a]	Argument descriptions.
-> String	Full program pathname.
-> [String]	Incoming program argument list.
-> Args a	Outgoing argument parse results.

Given a description of the arguments, parseArgs produces a map from the arguments to their "values" and some other useful byproducts. parseArgs requires that the argument descriptions occur in the order 1) flag arguments, then 2) positional arguments; otherwise a runtime error will be thrown.

parseArgsIO Source

Arguments

:: (Show a, Ord a, APCData b)
=> b	Degree of completeness of parse.
-> [Arg a]	Argument descriptions.
-> IO (Args a)	Argument parse results.

Most of the time, you just want the environment's arguments and are willing to live in the IO monad. This version of parseArgs digs the pathname and arguments out of the system directly.

Using parse results

Query functions permit checking for the existence and values of command-line arguments.

gotArg Source

Arguments

:: Ord a
=> Args a	Parsed arguments.
-> a	Index of argument to be checked for.
-> Bool	True if the arg was present.

Check whether a given optional argument was supplied. Works on all types.

class ArgType b where Source

Type of values that can be parsed by the argument parser.

Minimal complete definition

getArg

Methods

getArg Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> Maybe b	Argument value if present.

Fetch an argument's value if it is present.

getRequiredArg Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> b	Argument value.

Fetch the value of a required argument.

Instances

ArgType Double Source
ArgType Float Source
ArgType Int Source
ArgType Integer Source
ArgType () Source
ArgType ArgFileOpener Source
ArgType [Char] Source

getArgString Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> Maybe String	Argument value if present.

Deprecated: Return the String value, if any, of the given argument.

getArgFile Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> IOMode	IO mode the file should be opened in.
-> IO (Maybe Handle)	Handle of opened file, if the argument was present.

Deprecated: Treat the String value, if any, of the given argument as a file handle and try to open it as requested.

getArgStdio Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> IOMode	IO mode the file should be opened in. Must not be `ReadWriteMode`.
-> IO Handle	Appropriate file handle.

Treat the String value, if any, of the given argument as a file handle and try to open it as requested. If not present, substitute the appropriate one of stdin or stdout as indicated by IOMode.

getArgInteger Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> Maybe Integer	Argument value if present.

Deprecated: Return the Integer value, if any, of the given argument.

getArgInt Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> Maybe Int	Argument value if present.

Deprecated: Return the Int value, if any, of the given argument.

getArgDouble Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> Maybe Double	Argument value if present.

Deprecated: Return the Double value, if any, of the given argument.

getArgFloat Source

Arguments

:: (Show a, Ord a)
=> Args a	Parsed arguments.
-> a	Index of argument to be retrieved.
-> Maybe Float	Argument value if present.

Deprecated: Return the Float value, if any, of the given argument.

newtype ArgFileOpener Source

ArgType instance for opening a file from its string name.

Constructors

ArgFileOpener
Fields argFileOpener :: IOMode -> IO Handle Function to open the file

Instances

ArgType ArgFileOpener Source

Misc

data ParseArgsException Source

This exception is raised with an appropriate error message when argument parsing fails. The first argument is the usage message, the second the actual error message from the parser.

Constructors

ParseArgsException String String

Instances

Eq ParseArgsException Source
Show ParseArgsException Source
Exception ParseArgsException Source

baseName Source

Arguments

:: String	Pathname.
-> String	Rightmost component of pathname.

Return the filename part of a pathname. Unnecessarily efficient implementation does a single tail-call traversal with no construction.

parseError Source

Arguments

:: String	Usage message.
-> String	Specific error message.
-> a	Bogus polymorphic result.

Generate a usage error with the given supplementary message string.

usageError :: Ord a => Args a -> String -> b Source

Generate a usage error with the given supplementary message string.

data IOMode :: *

See openFile

Constructors

ReadMode
WriteMode
AppendMode

Instances

Enum IOMode
Eq IOMode
Ord IOMode
Read IOMode
Show IOMode
Ix IOMode