Fix File object.

File.h

@@ -22,6 +22,7 @@ namespace coreutils {
       void setBufferSize(size_t size);
       void read();
       void write(std::string data);
+      void write(coreutils::ZString &data);
       std::string asString();
 
       char *buffer;
@@ -30,6 +31,7 @@ namespace coreutils {
       std::string fileName;
 
     private:
+      void open(std::string fileName, int mode, int authority);
       int fd;
 
    };