cmdargs

System.Console.CmdArgs.Explicit

Contents

Description

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.

Synopsis

Running command lines

Constructing command lines

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