Resume reading from iostream::cin after Ctrl+Z (EOF)? (“ignore” doesn't work)

问题

Why does the outer loop in the following program terminate when we provide ctrl+z for the inner loop only?

#include<iostream>
int main()
{
    string s1,s2;

    while(cin >> s1)
    {
        cout<<"In loop1\n";
        while(cin>>s2)
            cout<<"In loop 2\n";
        cin.ignore();
    }
}

回答1:

Hitting Ctrl+z (on Windows) closes the standard input stream. Once it's closed, it stays closed. It doesn't magically reopen once the inner loop is finished. There's just no reason why it would.

回答2:

Ctrl-Z puts cin into an error state so cin.ignore does nowt. try cin.Clear() instead.

来源：https://stackoverflow.com/questions/10147996/resume-reading-from-iostreamcin-after-ctrlz-eof-ignore-doesnt-work