CSC 1060 Week 8: File Read and Streams

Course Information

• Course name: CSC 1060
• Topics: Repetition and File Read

Objectives

• Read data from a file using stream objects
• Read all data from a file into a program

Agenda (Week 8)

• Streams (iostream, fstream)
• Disconnected Model: File Input
• StringStream (sstream)
• Review Exercises
• TODO
• Resources for Help

Streams

• Represent data flowing into or out of a program
• Input (extraction):
  • Keyboard
  • File input (reading data from a file)
  • Moves data from source to program
• std::cin: Represents the keyboard input
• std::ifstream: Represents input from a data file

Common Input Functions (istream & ifstream)

• peek: Peek next character
• ignore: Extract and discard characters
• good: Check if stream state is good
• fail: Check if failbit or badbit is set
• ! (operator): Evaluate stream (not)
• eof: Check if eofbit is set
• clear: Set error state flags (default is goodbit)

• (operator): Extract formatted input

Reading from std::istream

• Read data from the keyboard until whitespace into variables (int, float, double, etc.)
• Example: std::cin >> var;
• Read data from keyboard until Enter key into a string object
• Example: std::string str; std::getline(std::cin, str);

5-Step Disconnected Model (for Reading from a File)

• Reading from a file involves connecting to it, processing, and disconnecting.
• Steps
  1. Create input file stream object (std::ifstream)
  2. Open the file for reading
  3. Check if the file opened successfully
  4. Read data from the file
  5. Close the file stream to disconnect

Creating the File Object (Step 1)

• Create a std::ifstream object.
• Include the <fstream> library

Opening the File (Step 2)

• Link the filestream object to a specific file that has been created externally
• Must specify the filename with extension e.g. "MyData.txt"
• Use .open() method: readFile.open("fileName.dat");

Checking file Status (Step 3)

• Check if the file was successfully opened using !readFile, .good(), or .fail()
• Provide an error message and return 1 if the file did not open, for error handling.

Reading from the File (Step 4)

• Reading data until whitespace:readFile >> var;
• Reading line by line with std::string: std::getline(readFile, str);
• Reading until the end of file (EOF):
  • Use a sentinel controlled while loop.
  • Example: while (!readFile.eof()) { readFile >> var; ... }

Closing the File (Step 5)

• Use .close() method to disconnect from the file: readFile.close();

Review Tutorials

• Complete the 15.2 Streams, 15.3 File Input, 15.4 File Output tutorials and engagement activities.

Review Exercises

• Complete Parsons exercises (problems 1-10, try at least 3).
• Change question type to Parsons (may need to switch to "Active Write" first).
• Parsons questions involve dragging and dropping code snippets.

Using Stringstream

• Understand the <sstream> library's classes: std::stringstream, std::ostringstream, std::istringstream.
• Work through the corresponding CodeHS tutorial.