Haskell从文件句柄读取
示例
像在I/O库的其他几个部分中一样，隐式使用标准流的函数在System.IO执行相同工作时具有对等的功能，但是左侧有一个额外的参数，类型为Handle，表示正在处理的流。例如，getLine::IOString有一个对应项hGetLine::Handle->IOString。
import System.IO( Handle, FilePath, IOMode( ReadMode ),
openFile, hGetLine, hPutStr, hClose, hIsEOF, stderr )
import Control.Monad( when )
dumpFile :: Handle -> FilePath -> Integer -> IO ()
dumpFile handle filename lineNumber = do -- show file contents line by line
end <- hIsEOF handle
when ( not end ) $ do
line <- hGetLine handle
putStrLn $ filename ++ ":" ++ show lineNumber ++ ": " ++ line
dumpFile handle filename $ lineNumber + 1
main :: IO ()
main = do
hPutStr stderr "输入文件名： "
filename <- getLine
handle <- openFile filename ReadMode
dumpFile handle filename 1
hClose handle文件内容example.txt：
This is an example. Hello, world! This is another example.
输入：
输入文件名： example.txt
输出：
example.txt:1: This is an example. example.txt:2: Hello, world! example.txt:3: This is another example