how can I remove the quotes from a string in the output of a file in haskell

Instance show for [a] is based on the definition of show for a and Show String always puts double quotes around String .

You can omit the double quotes by writing your own version of the function:

import Data.List

myShow :: [String] -> String
myShow strs = concat [ "[", intercalate "," strs, "]" ]

You can also reuse the instance Show [a] using a newtype wrapper to change the instance that ghc selects:

newtype NoDoblesComillas = NDC { getString :: String }

instance Show NoDoblesComillas where
  show = getString -- usando el string directamente

myShow :: [String] -> String
myShow = show . fmap NDC