Simple file input and output

Simple file input and output

• Include the header file fstream
• Ofstream class defines the output for processing a
• Ofstream need to declare one or more variables, and ofstream objects associated with the file.
• Wherein an association method using open () method, after using the file using the close () Close method.
• Ofstream objects and can use the << operator outputs various types of data.
• Note, ofstream must declare themselves.

ofstream outFile;
outFile.open("fish.txt");
outFile << "hhhh"<<endl; //向文件中输入一行文本

• ofstream object can use any method to cout.
• open () function
  • If you run before the file does not exist, create the file. If there are changes to its length is 0 (empty).
  • open () may fail to open.
• Fstream header file that contains the file read
• Ifstream defines a class for processing input
• Need to declare ifstream object.
• Ifstream objects need to be associated with the file, use the open () method.
• Use close () method to close.
• Ifstream >> used to read various types of data.
• get ifstream object () method to read a character. Use getline () reads a line of characters.
• It may be combined and used ifstream eof (), fail () determines whether or not successful or the like.
• When ifstream object itself as a test condition, if the last read operation was successful, it is converted to type bool

ifstream inFile;
inFile.open("bowling.txt");
double wt;
inFile >> wt;
char line[81];
inFile.getline(line, 81);

• Use is_open () to determine whether the file is opened. exit () function is defined in the header file cstdlib. If the compiler does not support is_open (), you can use the older good () instead.

inFile.open("bowling.txt");
if (!inFile.is_open())
{
    exit(EXIT_FAILURE);
}

• An error occurred during reading
  • If you encounter EOF, eof () function returns true
  • Encountered type mismatch or EOF, fail () returns true
  • Returns true if the disk is damaged or corrupted files, bad ()
  • If you want to simply determine whether the reading is successful, the use of good (). Returns true on success

  inFile >> value;
  while(inFile.good())
  {
    //...
    inFile >> value;
  }
  //另一种简洁写法
  while(inFile >> value)
  {
    //...
  }