Announcing HSH, the Haskell Shell

June 7th, 2006

Following the “release early, release often” motto, I am happy to announce version 0.1.0 of HSH, the Haskell shell.


You may obtain it with:


darcs get --tag 0.1.0 http://darcs.complete.org/hsh


Things are still very rough in many ways, but this version already lets you:


  • Run commands
  • Pipe things between commands
  • Pipe command input/output into and out of pure Haskell functions
  • Pure Haskell functions are as much a first-class citizen as is grep or cat


Here is an example session: (some lines wrapped for readability)


$ ghci -fglasgow-exts HSH

*HSH> run $ ("ls", ["."])
COPYING    HSH        HSH.hs    TODO    announcements  testsrc
COPYRIGHT  HSH.cabal  Makefile  _darcs  test.hs

*HSH> run $ ("ls", ["-l"]) -|- ("wc", ["-l"])
12

*HSH> :m +Text.Printf
*HSH Text.Printf> let countLines = (zipWith (\i line -> printf "%-5d %s" i line) 
       [(1::Int)..])::([String] -> [String])

*HSH Text.Printf> run $ ("ls", ["-l"]) -|- countLines -|- ("grep", ["hs$"])
6     -rw-r--r-- 1 jgoerzen jgoerzen  1285 Jun  6 09:43 HSH.hs
11    -rw-r--r-- 1 jgoerzen jgoerzen   565 Jun  6 09:43 test.hs

*HSH Text.Printf> :m +Data.List
*HSH Text.Printf Data.List> run $ ("ls", ["-l"]) -|- countLines -|- 
         filter (isSuffixOf "hs")
6     -rw-r--r-- 1 jgoerzen jgoerzen  1285 Jun  6 09:43 HSH.hs
11    -rw-r--r-- 1 jgoerzen jgoerzen   565 Jun  6 09:43 test.hs

*HSH Text.Printf Data.List> run $ ("ls", ["-l"]) -|- countLines -|- filter (isSuffixOf "hs") 
       -|- ("tr", ["a-z", "A-Z"])
6     -RW-R--R-- 1 JGOERZEN JGOERZEN  1285 JUN  6 09:43 HSH.HS
11    -RW-R--R-- 1 JGOERZEN JGOERZEN   565 JUN  6 09:43 TEST.HS

*HSH Text.Printf Data.List> let generator = \(_::String) -> unlines . map show $ [1..20]
*HSH Text.Printf Data.List> generator ""
"1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n"
*HSH Text.Printf Data.List> run $ generator -|- ("grep", ["1"])
1
10
11
12
13
14
15
16
17
18
19

Future versions will likely simplify syntax to make it easier to write scripts and introduce a sh to hsh converter. I also plan to add pure Haskell tools for some common shell-ish things that one could do in Haskell.

Categories: Programming

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Comments Feed3 Comments

  1. cliff

    John, about the example…My computer does stuff like that once in a while so I kind of have some experience here. Try shutting it off and then retart it. That’ll usually fix it.
    :}

    Reply

    John Goerzen Reply:

    Cliff, I should have just called you in the first place. Power cycling it would have been so much easier than writing a new shell ;-)

    Reply

  2. The Changelog

    Shell scripts are good for a lot of things. It’s quick and easy to design shell scripts that take input from one program, pass it to another program, munge it for filenames, etc.

    But there are a few drawbacks to shell scripts.

    The #1 drawback, in m

    Reply

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