Haskell: hGetChar: Read a charcater from file

hGetChar function takes a handle and read character from it. You may get isEOFError if the end of file has been reached.

Prelude System.IO> :t hGetChar

hGetChar :: Handle -> IO Char

Suppose ‘today.txt’ contains following data.

$ cat today.txt 
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
11, 12, 13, 14, 15, 16, 17, 18, 19, 20
21, 22, 23, 24, 25, 26, 27, 28, 29, 30
31, 32, 33, 34, 35, 36, 37, 38, 39 40

Following program takes a file as input and read it character by character.

FileUtil.hs

import System.IO

readDataFrom fileHandle = 
    do 
        isFileEnd <- hIsEOF fileHandle
        if isFileEnd 
            then
                return ("")
            else
                do
                    info <- hGetChar fileHandle
                    print info
                    readDataFrom fileHandle

main = 
    do
        putStrLn "Enter file name (Including full path) to read"
        fileName <- getLine
        fileHandle <- openFile fileName ReadMode

        readDataFrom fileHandle

$ runghc FileUtil.hs
Enter file name (Including full path) to read
today.txt
'1'
','
' '
'2'
','
' '
'3'
','
' '
'4'
','
' '
'5'
','
' '
'6'
','
' '
'7'
','
' '
'8'
','
' '
'9'
','
' '
'1'
'0'
'\n'
'1'
'1'
','
' '
'1'
'2'
','
' '
'1'
'3'
','
' '
'1'
'4'
','
' '
'1'
'5'
','
' '
'1'
'6'
','
' '
'1'
'7'
','
' '
'1'
'8'
','
' '
'1'
'9'
','
' '
'2'
'0'
'\n'
'2'
'1'
','
' '
'2'
'2'
','
' '
'2'
'3'
','
' '
'2'
'4'
','
' '
'2'
'5'
','
' '
'2'
'6'
','
' '
'2'
'7'
','
' '
'2'
'8'
','
' '
'2'
'9'
','
' '
'3'
'0'
'\n'
'3'
'1'
','
' '
'3'
'2'
','
' '
'3'
'3'
','
' '
'3'
'4'
','
' '
'3'
'5'
','
' '
'3'
'6'
','
' '
'3'
'7'
','
' '
'3'
'8'
','
' '
'3'
'9'
' '
'4'
'0'
'\n'

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