Exception Handling and Opening a File?

问题

Is it possible to use exceptions with file opening as an alternative to using .is_open()?

For example:

ifstream input;

try{
  input.open("somefile.txt");
}catch(someException){
  //Catch exception here
}

If so, what type is someException?

回答1:

http://en.cppreference.com/w/cpp/io/basic_ios/exceptions

Also read this answer 11085151 which references this article

// ios::exceptions
#include <iostream>
#include <fstream>
using namespace std;

void do_something_with(char ch) {} // Process the character 

int main () {
  ifstream file;
  file.exceptions ( ifstream::badbit ); // No need to check failbit
  try {
    file.open ("test.txt");
    char ch;
    while (file.get(ch)) do_something_with(ch);
    // for line-oriented input use file.getline(s)
  }
  catch (const ifstream::failure& e) {
    cout << "Exception opening/reading file";
  }

  file.close();

  return 0;
}

Sample code running on Wandbox

EDIT: catch exceptions by const reference 2145147

EDIT: removed failbit from the exception set. Added URLs to better answers.

回答2:

From the cppreference.com article on std::ios::exceptions

On failure, the failbit flag is set (which can be checked with member fail), and depending on the value set with exceptions an exception may be thrown.

来源：https://stackoverflow.com/questions/9670396/exception-handling-and-opening-a-file