Haskell Language IO Reading from `stdin`
Example
As-per the Haskell 2010 Language Specification, the following are standard IO functions available in Prelude, so no imports are required to use them.
getChar :: IO Char - read a Char from stdin
-- MyChar.hs
main = do
myChar <- getChar
print myChar
-- In your shell
runhaskell MyChar.hs
a -- you enter a and press enter
'a' -- the program prints 'a'
getLine :: IO String - read a String from stdin, sans new line character
Prelude> getLine
Hello there! -- user enters some text and presses enter
"Hello there!"
read :: Read a => String -> a - convert a String to a value
Prelude> read "1" :: Int
1
Prelude> read "1" :: Float
1.0
Prelude> read "True" :: Bool
True
Other, less common functions are:
getContents :: IO String- returns all user input as a single string, which is read lazily as it is neededinteract :: (String -> String) -> IO ()- takes a function of type String->String as its argument. The entire input from the standard input device is passed to this function as its argument
