C++ fstream 类

示例

使用 fstream 读取和写入文件：

#include <iostream>
#include <fstream>
using namespace std;

int main() {
  // 创建并打开文本文件
  fstream MyFile("filename.txt");

  // 写入文件
  MyFile << "Files can be tricky, but it is fun enough!";
  
  // 从文件中读取数据
  string myText;
  getline(MyFile, myText);
  cout << myText;

  // 关闭文件
  MyFile.close();
} 

fstream MyFile("filename.txt");

MyFile.seekg(6)

将读取的文件指针移动到不同的位置：

MyFile.seekg(6, fstream::beg);
cout << MyFile.tellg() << "
";
MyFile.seekg(-3, fstream::cur);
cout << MyFile.tellg() << "
";
MyFile.seekg(-4, fstream::end);
cout << MyFile.tellg() << "
";

cout << MyFile.tellg();

MyFile.seekp(6)

将写入文件指针移动到不同的位置：

MyFile.seekp(6, fstream::beg);
cout << MyFile.tellp() << "
";
MyFile.seekp(-3, fstream::cur);
cout << MyFile.tellp() << "
";
MyFile.seekp(-4, fstream::end);
cout << MyFile.tellp() << "
";

cout << MyFile.tellp();

char myChar = MyFile.get();
cout << myChar;

char destination[20];
MyFile.get(destination, 20);
cout << destination << "
";

// 遇到“.”时停止阅读。
MyFile.get(destination, 20, '.');
cout << destination << "
";

char destination[20];
MyFile.getline(destination, 20);
cout << destination << "
";

// 遇到“.”时停止阅读。
MyFile.getline(destination, 20, '.');
cout << destination << "
";

string destination;
getline(MyFile, destination);
cout << destination << "
";

// 遇到“.”时停止阅读。
getline(MyFile, destination, '.');
cout << destination << "
";

char destination[20];
MyFile.read(destination, 19);
destination[20] = '\0'; //确保它以空终止符结尾。
cout << destination << "
";

char myChar = MyFile.peek();
cout << myChar;

char destination[20];
MyFile.getline(destination, 20);
cout << MyFile.gcount() << "
";

char myStr[] = "Hello World!";
MyFile.write(myStr, 5);

char grade = 'B';
MyFile.put(grade);

ofstream MyFile;
MyFile.open("filename.txt");

fstream MyFile;
cout << MyFile.is_open(); << "
"; // 显示 0，因为文件未打开。
MyFile.open("filename.txt");
cout << MyFile.is_open(); << "
"; // 显示 1，因为文件已打开

MyFile.close();

filebuf * buf = MyFile.rdbuf();

语法

MyFile >> variable

MyFile >> variable1 >> variable2 >> variable3

示例

使用操纵符来改变数据的解读方式：

bool myBool;
int myInt;

// 将字符序列"true"和"false"解释为布尔值
MyFile >> boolalpha >> myBool;

// 恢复正常读取布尔值。
MyFile >> noboolalpha;

// 从文件中读取十六进制数并将其解释为整数
MyFile >> hex >> myInt;

// 恢复正常读取整数的方式
MyFile >> dec;

int year = 2024;
MyFile << year << "
";
MyFile << "Files can be tricky, but it is fun enough!";