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Very newb question about std::cin

Posted on 2003-11-19
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Last Modified: 2010-04-02
I used:

std::cin >> someStdStringVar;

and then I follow it up with another prompt and

std::cin.getline(someCharArray,maxCharsToExtract);

If you've used std::cin frequently you'll know that this won't work. There are still characters left in the buffer (2 in my case) and my bet is that they are the \r\n pair not stored into someStdStringVar previously.

The only way I managed to get them out of there was to add another getline() call before the one I'm interested in.

I tried std::cin.seekg(0,std::ios_base::end); and also std::cin.ignore(INFINITE); before the call to getline() but both caused the following call to getline() to fail to block while waiting for input and filled the buffer with nothing.

I don't mind calling getline() and extra time, but it seems crude. Why is seekg() not working as I expect it to?

thanks,
-Sandra

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Question by:Sandra-24
5 Comments
 
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Accepted Solution

by:
SteH earned 300 total points
ID: 9785392
I would guess that
std::cin.ignore (INFINITE, '\n');
should work. From cin I wouldn't expect any EOF since it is a stream but not a file.
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Author Comment

by:Sandra-24
ID: 9785466
Nope does the same as the rest :(

Using cin is not as simple as it looks.
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Expert Comment

by:Hoegje
ID: 9785481
maybe this will help :

std::cin.flush(); // flush the complete stream

Not sure though !
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Assisted Solution

by:rstaveley
rstaveley earned 200 total points
ID: 9786071
This works for me, Sandra:
--------8<--------
#include <iostream>
#include <limits>

int main()
{
        std::string str1,str2;
        using std::cin;
        const int INFINITE = std::numeric_limits<int>::max();

        cin >> str1;
        cin.ignore(INFINITE,'\n');
        getline(cin,str2);
        std::cout << "str1 [" << str1 << "]\nstr2 [" << str2 << "]\n";
}
--------8<--------

Can you post a simple example of your problem?
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LVL 3

Author Comment

by:Sandra-24
ID: 9789633
You guys are right. The trouble was that I didn't define INFINITE in my program. Ordinarily that would prevent it from compiling, but it worked because a define of INFINITE does exist 0xFFFFFFFF which proabably wrapped to a negative number (or so I'm guessing). At any rate it's working now, thanks!
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