C++: Using ifstream with getline();

问题:

Check this program

ifstream filein("Hey.txt");
filein.getline(line,99);
cout<<line<<endl;
filein.getline(line,99);
cout<<line<<endl;
filein.close();

The file Hey.txt has alot of characters in it. Well over a 1000

But my question is Why in the second time i try to print line. It doesnt get print?

回答1:

According to the C++ reference (here) getline sets the ios::fail when count-1 characters have been extracted. You would have to call filein.clear(); in between the getline() calls.

回答2:

The idiomatic way to read lines from a stream is thus:

{
    std::ifstream filein("Hey.txt");

    for (std::string line; std::getline(filein, line); )
    {
        std::cout << line << std::endl;
    }
}

Note:

• No close(). C++ takes care of resource management for you when used idiomatically.

• Use the free std::getline, not the stream member function.

回答3:

As Kerrek SB said correctly There is 2 possibilities: 1) Second line is an empty line 2) there is no second line and all more than 1000 character is in one line, so second getline has nothing to get.