CmdArgs

CmdArgs is a Haskell library for defining command line parsers. The two features that make it a better choice than the standard getopt library are:

  1. It's very concise to use. The HLint command line handling is three times shorter with CmdArgs.
  2. It supports programs with multiple modes, such as darcs or Cabal.

A very simple example of a command line processor is: 

data Sample = Sample {hello :: String}
              deriving (Show, Data, Typeable)

sample = mode $ Sample{hello = def &= text "World argument" & empty "world"}

main = print =<< cmdArgs "Sample v1, (C) Neil Mitchell 2009" [sample]

Despite being very concise, this processor is already fairly well featured: 

$ runhaskell Sample.hs --hello=world
Sample {hello = "world"}

$ runhaskell Sample.hs --help
Sample v1, (C) Neil Mitchell 2009

sample [FLAG]

  -? --help[=FORMAT]  Show usage information (optional format)
  -V --version        Show version information
  -v --verbose        Higher verbosity
  -q --quiet          Lower verbosity
  -h --hello=VALUE    World argument (default=world)

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