File I/O

• fstream Library
  • Streams:  An abstract way of thinking about I/O
    • A file "stream" is a sequence of symbols, e.g., This is a stream .... that is about to end. <EOF>
    • cin and cout are familiar streams for I/O
      • Other "standard" streams are cerr (unbuffered) and clog (buffered)
    • Ordinarily cin is associated with the keyboard and cout, cerr, and clog are associated with the monitor.  This can be changed with re-direction (see linux_II)
    • File I/O:  We can read and write files, using the common stream operators "<<" and ">>" by using the fstream library (keep in mind you "use" a library by including it and then referencing it's objects)
      • Some of the objects in fstream are:  ifstreams (input files) and ofstreams (output files) and fstreams (input-output files)
      • Opening Files:  stream files are opened either when they are declared or with the member function open()
        • e.g.:  ifstream input_file("filename"); or
        • e.g.:  ofstream output_file; ...... output_file.open("filename");
        • e.g.: fstream io_file; string "filename"; ...... io_file.open(filename.c_str());
      • Reading/Writing to Files:  stream files are read/written in the exact same manner as cin ro cout using the stream operators "<<" and ">>"
        • e.g.:  input_file >> variable;
        • e.g.:  output_file << variable;
      • Closing Files:  stream files are closed either when the program terminates or with the member function close()
        • e.g.:  input_file.close();
      • See file_io_example.cpp