[Haskell-cafe] commandline parsing?
ndmitchell at gmail.com
Sat Jul 29 09:19:22 EDT 2006
Have you seen: System.Console.GetOpt
Interestingly Hoogle doesn't seem to index it, but it does exist! (and
in fact Hoogle even uses it...)
On 7/29/06, Marc Weber <marco-oweber at gmx.de> wrote:
> I've been using pesco_cmdline for a while now. But I did notice that
> it doesn't fit my needs.. And it took me quite a while to get to know
> why I was getting strange typeable errors when specifying the wrong
> default value or reading the wrong type.. (these errors occur at
> runtime thus they don't use haskells strength)
> So I got another crazy idea. Why not see arguments as tokens and use a
> parser such as parsec?
> All you would have to do is creating some kind of syntax tree.
> Consider an example application : mmewcde (my mega executable which can
> do everything).
> mmewcde edit <file>
> mmewcde mv <file> <file>
> mmewcde mv --target-dir <dest> <folder> <files>>
> mmewcde cp <file> <file>
> mmewcde cp --target-dir <dest> <folder> <files>>
> mmewcde callsox <infile> <options> <outfile>
> Why not something like tar?
> mmewcde tar <x|c|f|v>* ..?
> Of cause I'll have to write the funtions
> edit :: String -> IO ()
> mv :: String -> String -> IO ()
> mvDest :: String -> [String] -> IO ()
> which have to be called
> Now I'd like to do this:
> optionParser = many $ oneOf [ edit, mv, mvDest, cp, cpDest, callsox, tar]
> optionParserWithHelp = optionParser <|> printHelp
> edit = do
> string "edit"
> file <- existingFilename
> launchEditor file
> mv = [..]
> mvDest = do
> string mv
> string "--target-dir"
> td <- existingDirectory
> files <- many existingFilename
> map (movefile td) files
> printHelp = do
> oneOf $ map string ["-h","--help","--usage"]
> prettyPrint optionParser
> main = do
> args <- getArgs
> parseAndExecute optionParserWithHelp
> prettyPrint might look like this (this will be unncommon ;)
> mmewcde --help:
> edit <exitingfile> or
> mv <exitingfile> <file>
> Would this be nice? Does this already exist somehow?
> perhaps many can even be made nongreedy so that you can specify more
> than one command at once
> mmewcde mv --target-dir d f1 f2 cp --target-dir d2 f3 f4 ...
> Does this make sense?
> I think this would lead to self documenting well mantainable code.
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