Opens a file for writing data, with the provided path name. Both absolute and relative path names are supported. The file is created if it does not exist already. If it already exists, its current content is either overwritten (overwrite option) or kept (append option). Writes the provided string to the currently open file. Writes the provided string to the currently open file, and terminates current line. Terminates current line. Flushes possibly unwritten data to the file system. Closes current file, flushing possibly unwritten data. Any further writing to the file requires to re-open it. True when a file has been successfully open or created for writing, false otherwise. True if no file is currently open for writing, false otherwise. True if the designated file exists, false otherwise. True if the designated file does not exists, false otherwise.