Use Haskell for shell scripting
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Use Haskell for shell scripting
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Re: Use Haskell for shell scripting
#2The tutorial does a great job of explaining why this is interesting: http://hackage.haskell.org/package/turtle-1.0.0/docs/Turtle-...
For example, the pwd function returns a FilePath type rather than a String:
Prelude Turtle> :type pwd
pwd :: IO Turtle.FilePath
Prelude Turtle> :type datefile
datefile :: Turtle.FilePath -> IO UTCTime
Re: Use Haskell for shell scripting
#3But why "turtle"?
Re: Use Haskell for shell scripting
#4Who's the target audience of this exactly? I already see a language pragma, do notation, liftIO, parser combinators.
Hamming has this great set of lectures on how he became a world renowned scientist and in one of the lectures he explains why Ada failed and other languages succeeded. The difference was that Ada was designed logically and most successful languages were designed psychologically. Even when government contracts mandated Ada people still wrote in Fortan and hand translated to Ada. You can watch the videos and take from it what you will.
A minimal bash file is`#!/bin/bash`. A minimal turtle file is already way too long and logical.
The set of videos: https://www.youtube.com/playlist?list=PL2FF649D0C4407B30.
Re: Use Haskell for shell scripting
#5But why "turtle"?
Turtle shell.
Re: Use Haskell for shell scripting
#6no
Re: Use Haskell for shell scripting
#7This is awesome, I was actually looking for something like that out of sheer curiosity, but perhaps it'll make it into production at some point.
Re: Use Haskell for shell scripting
#8Who's the target audience of this exactly? I already see a language pragma, do notation, liftIO, parser combinators. Hamming has this great set of lectures on how he became a world renowned scientist and in one of the lectures he explains why Ada failed and other languages succeeded. The difference was that Ada was designed logically and most successful languages were designed psychologically. Even when government co…
Would it be possible to create a /bin/turtle script which prepends those import and language statements? That way all the boilerplate that's needed would be "main = do ...", which seems acceptable imo.
Re: Use Haskell for shell scripting
#9Thanks Gabriel Gonzalez! There is a comment on the blog post (by Chris Done) asking how it deals with piping. I really wonder about that too.
Some related projects:
- Joey Hess recently released a nice Haskell-to-sh compiler. I like this approach as the resulting sh scripts are runnable on pretty much every *nix. https://joeyh.name/blog/entry/shell_monad/
- Chris Done also released a lib to do shell stuff from Haskell, which build on the conduit library http://chrisdone.com/posts/shell-conduit
- Chris also wrote a shell in Haskell https://github.com/chrisdone/hell
- Then there is Shelly by Greg Weber https://github.com/yesodweb/Shelly.hs
There are probably more...
Re: Use Haskell for shell scripting
#10I don't really see the point of this, apart from academic research values.
POSIX shell is everywhere - your current Linux and OS X machines, old UNIX workstations, home routers, servers... Just drop in a file and it will probably run just fine, unless the author screwed something up completely. POSIX shell scripts are the perfect bootstrap mechanisms that will run almost anywhere regardless of architecture.
Haskell, on the other hand, is rarely present in an operating system - if you absolutely, positively need a higher-level language for „shell scripting”, then you have a much higher chance of finding a Perl interpreter, or even Python. Heck, even getting ghc and its' basic ecosystem running has always proved to be a huge burden to me. Try sticking a `cabal install` in your CI flow, you'll see your job times increase by hours.
Third, there's just the KISS aspect of it - if you're writing something that has logic so simple it can be stuck in a shell file, why not just write it in a shell file? You don't need category theory to get a few files installed...