Hi, I have small code snippet to read content of a file, which should grow into simple tool to read temperature from sensor on Raspberry Pi: module Main where import System.Environment main :: IO () main = do [f] <- getArgs s <- readFile f putStr s When this is called with the test file I have copied from the real location it works fine: $ cat /sys/bus/w1/devices/28-000004e46240/w1_slave >test.txt $ ./ds18b20 test.txt 53 01 4b 46 7f ff 0d 10 e9 : crc=e9 YES 53 01 4b 46 7f ff 0d 10 e9 t=21187 How ever when called with the real location nothing happens: $ ./ds18b20 /sys/bus/w1/devices/28-000004e46240/w1_slave Can someone help? I have thought that the file is not properly ended so I have tried to take just first line but that doest work either. Thanks Libor