|Maintainer||John Goerzen <firstname.lastname@example.org>|
Copyright (c) 2006 John Goerzen, email@example.com
Welcome to HSH, the Haskell Shell infrastructure.
HSH is designed to let you mix and match shell expressions with Haskell programs.
Here are a few examples to get you started:
run $ "echo /etc/pass*" :: IO String -> "/etc/passwd /etc/passwd-" runIO $ "ls -l" -|- "wc -l" -> 12 runIO $ "ls -l" -|- wcL -> 12 runIO $ ("ls", ["-l", "file with spaces.txt"]) glob "~jgoerzen" >>= cd . head
wcL is a pure Haskell function defined in HSH.ShellEquivs.wcL as:
wcL :: [String] -> [String] wcL inp = [show $ genericLength inp]
Here's another example:
let countLines = (zipWith (\i line -> printf "%-5d %s" i line) [(1::Int)..])::([String] -> [String]) runIO $ ("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
You can run a command with HSH in several ways:
- By using
runin a context that expects IO (), which will leave the final standard output going to the normal standard output of the program
- By using
runin a context that expects a String, which will capture standard output into a buffer and present it as a String
- Any of the numerous other methods documented in
- The shortcut functions
runIOlets you run a command and force the context IO (), which is a frequently-useful shortcut when you don't care about the result.
runSLgrabs the first line of output in the result.
You can then specify a command, which could be a single command or a command joined together with pipes.
There are many different items that make valid types; see the list of
ShellCommand for a full list. Here are a few:
- A simple bare string is passed to the shell for execution. The shell will then typically expand wildcards, parse parameters, etc.
(String, [String])tuple. The first item in the tuple gives the name of a program to run, and the second gives its arguments. The shell is never involved. This is ideal for passing filenames, since there is no security risk involving special shell characters.
- A Haskell function. This function will accept input representing
its standard input and generate output to go to stdout. Function
types that are supported natively include
(String -> String),
(String -> IO String),
([String] -> [String]),
([String] -> IO [String]). Those that accept a
[String]type will have each string in the list representing a single line.
Pipes can be constructed by using the -|- operator, as illustrated above. It is quite possible to pipe data between Haskell functions and shell commands at will.
In addition, HSH.ShellEquivs provides a number of useful pure-Haskell equivalents of regular shell commands.
For more information, please consult the other modules in HSH as well as the HSH wiki at: