Detailed explanation of C++ function library: Detailed explanation of extended system functions

C function library provides extended system functions, including file system processing, system command execution, date and time operations, network programming, etc. For example, you can use the find_first_of function to find files with a specific extension in a directory.

Detailed explanation of C function library: extended system functions

C function library provides a series of extended system functions that enhance C The ability to interact with the underlying system.

File system processing

#include <fstream>

void readFile(const char* fileName) {
  std::ifstream inputFile(fileName);
  if (inputFile.is_open()) {
    std::string line;
    while (std::getline(inputFile, line)) {
      // Process the line
    }
    inputFile.close();
  } else {
    // Error handling
  }
}

System command execution

#include <cstdlib>

void executeCommand(const char* command) {
  system(command);
}

Date and time operations

#include <ctime>

void printCurrentDate() {
  time_t now = time(0);
  tm *ltm = localtime(&now);
  printf("Current date: %d/%d/%d", ltm->tm_mon + 1, ltm->tm_mday, 1900 + ltm->tm_year);
}

Network Programming

#include <iostream>
#include <boost/asio.hpp>

void startServer(int port) {
  boost::asio::io_service ioService;
  boost::asio::ip::tcp::acceptor acceptor(ioService, boost::asio::ip::tcp::endpoint(boost::asio::ip::tcp::v4(), port));
  for (;;) {
    boost::asio::ip::tcp::socket socket(ioService);
    acceptor.accept(socket);
    // Handle client connection
  }
}

Practical Case: File Search

Suppose we have a file named findFile.cpp A C program that uses the find_first_of function from the library to find files containing a specific extension in a directory:

#include <iostream>
#include <filesystem>

int main() {
  std::string directory = "/path/to/directory";
  std::string extension = ".txt";
  for (const auto& entry : std::filesystem::recursive_directory_iterator(directory)) {
    if (entry.is_regular_file() && entry.path().extension() == extension) {
      std::cout << entry.path() << std::endl;
    }
  }
  return 0;
}

by calling boost::filesystem::recursive_directory_iterator Get the traverser of all files and subdirectories in the directory, and use entry.path().extension() to get the extension of the file, and then compare it with the specified extension to find the satisfaction conditional file.

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