What are the file and path classes in the C++ library?

The file and path classes are classes in the C standard library used to operate files and paths. File classes include ifstream (read text files), ofstream (write text files), fstream (read and write text files), ofstream (write binary files), and ifstream (read binary files). Path classes include path (representing a file or directory path) and directory_entry (representing file system entry information). In a practical application, a file can be opened for reading and writing, the file contents can be read line by line, and the contents can be written to other files.

File and path classes in C function library

C The standard library provides many files for operating files and paths System library. Here are some commonly used classes:

File class

• std::ifstream: used to read text files.
• std::ofstream: used to write text files.
• std::fstream: Can be used for both reading and writing text files.
• std::ofstream: used to write binary files.
• std::ifstream: used to read binary files.

Path class

• std::filesystem::path: Represents the path of a file or directory.
• std::filesystem::directory_entry: Represents information about entries in the file system, including files, directories, or symbolic links.

Practical case

Consider the following scenario: read the contents of a text file named "input.txt" and write it to "output. txt" file.

#include <fstream>

int main() {
  // 打开 "input.txt" 文件进行读取
  std::ifstream input_file("input.txt");

  // 检查文件是否已成功打开 
  if (!input_file.is_open()) {
    // 文件未打开，处理错误
  }

  // 打开 "output.txt" 文件进行写入
  std::ofstream output_file("output.txt");

  // 检查文件是否已成功打开 
  if (!output_file.is_open()) {
    // 文件未打开，处理错误
  }

  // 从 "input.txt" 按行读取内容
  std::string line;
  while (std::getline(input_file, line)) {
    // 将读取的行写入 "output.txt"
    output_file << line << "\n";
  }

  // 关闭文件
  input_file.close();
  output_file.close();

  return 0;
}

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