freopen()等效于c ++流

Question

使用c-style i/o进行编程时,我有时会使用freopen()重新打开stdin进行测试,这样我就不必重复输入输入.我想知道是否有相当于c ++的i/o流.此外,我知道我可以使用管道在命令行/终端/任何炎症上重定向它但我想知道是否有办法在我的代码中执行它(因为你可以看到,我不是很了解CL/T/W).

Answer 1

freopen也适用于cin和cout.无需搜索新内容.

freopen("input.txt", "r", stdin); // redirects standard input
freopen("output.txt", "w", stdout); // redirects standard output

int x;
cin >> x; // reads from input.txt
cout << x << endl; // writes to output.txt

编辑:从C++标准27.3.1:

对象cin控制与声明的对象stdin相关联的流缓冲区的输入<cstdio>.

所以根据标准,如果我们重定向stdin它也会重定向cin.反之亦然cout.

Answer 2

#include <iostream>
#include <fstream>

int main() {

  // Read one line from stdin
  std::string line;
  std::getline(std::cin, line);
  std::cout << line << "\n";

  // Read a line from /etc/issue
  std::ifstream issue("/etc/issue");
  std::streambuf* issue_buf = issue.rdbuf();
  std::streambuf* cin_buf = std::cin.rdbuf(issue_buf);
  std::getline(std::cin, line);
  std::cout << line << "\n";

  // Restore sanity and read a line from stdin
  std::cin.rdbuf(cin_buf);
  std::getline(std::cin, line);
  std::cout << line << "\n";
}

http://www.cplusplus.com/reference/iostream/ios/rdbuf/