Newbie's question: I want to ls the filenames of a directory. The program in C is something like:

#include <direnet.h>

int main(){
   DIR *dp;
   struct dirent *dirp;

   dp = opendir("/");

   while((dirp = readdir(dp)) != NULL)
       printf("%s\n", dirp->d_name);

   closedir(dp);
}

and I write that in haskell:

-----
import System.Posix
import System.IO

main = do
    dp <- openDirStream "/"
df <- readDirStream dp
    putStrLn df
    closeDirStream dp

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It can print the first entry of the dir, but how can we list it all like the C prog? map ? list comperhension?