runhugs [option...] file [argument...]
The runhugs command is an interpreter for an executable Hugs
script.
The first non-option should be the name of a file containing a Haskell
Main module.
The runhugs command will invoke the
the main function in this module, with any subsequent
arguments available through the getArgs action.
For example, suppose we have a file echo.hs containing
module Main where
import System.Environment
main = do
args <- getArgs
putStrLn (unwords args)
Then we can run this program with the command
runhugs echo.hs a b cWe can also test the program from within the interpreter using the
withArgs function from the
System.Environment module:
Main> withArgs ["a", "b", "c"] main a b c
On Unix systems, it is possible for an executable file to specify which program is used to run it. To do this we need to make the module a literate script, like the following:
#! /usr/local/bin/runhugs +l > module Main where > import System.Environment > main = do > args <- getArgs > putStrLn (unwords args)If this file is called myecho, and is executable, we can say
myecho a b cThis invokes the command
/usr/local/bin/runhugs +l myecho a b cThe
+l option tells
runhugs that myecho contains a
literate script,
even though its name does not end in ".lhs".Note: Unfortunately, the #! feature passes additional arguments (if any) to the program as a single argument: if the first line were
#! /usr/local/bin/runhugs +l -98then the first argument to runhugs would be "+l -98". You can get around this using the-Xoption, which asks for the string to be split into options:#! /usr/local/bin/runhugs -X +l -98Then the program will read and act on both the+land-98options.