On 8/27/06, Donald Bruce Stewart <[EMAIL PROTECTED]> wrote:
djsenda: > Hi, I use the operation 'readFile' for obtain information locates on > a file. When I try to write another information on the same file, I > obtain this error message: "openFile: permision denied". I found this: > "The readFile operation holds a semi-closed handle on the file until > the entire contents of the file have been consumed. It follows that an > attempt to write to a file (using writeFile, for example) that was > earlier opened by readFile will usually result in failure with > isAlreadyInUseError." in this web > http://www.haskell.org/onlinereport/io.html. > > How can I break that semi-closed handle for to write in the > preaviously readed file? Thank you.Due to lazy IO, you'll need to either read the entire file first, before you can safely write to that file, (or explicitly close the Handle): import Control.Exception main = do s <- readFile "x" evaluate $ length s -- evaluate the list, reading it in writeFil e "x" (reverse s)
GHCi says me that: evaluate is not in scope
Here we use 'evaluate (length s)' to explictily force the entire file to be read, which will close the Handle, and allows us to safely write back to the same file. -- Don P.S. Learning Haskell questions are better addressed to haskell-cafe@haskell.org
Ok, for another question I will write in this mailing list. _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
