Input being chopped off

Question

This code looks simple, right?

string password;
cin.ignore();
getline(cin, password);
cout << "The user inputted the password: " << password << endl;

Well for some reason when i type in "secret" as the password the cout results in only "ecret", i.e. it is chopping off the first character every time. Why is this?

@chris Oh thank you, I had a misunderstanding on how that function works :) — Axel Kennedal, Apr 10 '14 at 16:37

score 1 · Answer 1 · edited May 23 '17 at 10:25

1

cin.ignore() ignores the next character of input. That means the s in secret. I imagine the call is there because of previous troubles of getline seeming to skip input (see this question). This only applies when operator>> is used and leaves a newline beforehand. I recommend instead doing:

getline(std::cin >> std::ws, password);

This will remove troubles over leftover whitespace and not cause problems when there is none.

edited May 23 '17 at 10:25

Community

1
1

answered Apr 10 '14 at 16:42

chris

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What is that "std:ws"? I get the rest though, thanks! – Axel Kennedal Apr 10 '14 at 16:53
@AxelKennedal-TechTutor, It extracts leading whitespace. – chris Apr 10 '14 at 16:57
Extracts? Could you explain from the top to the bottom how that line works? :) – Axel Kennedal Apr 10 '14 at 19:16
@AxelKennedal-TechTutor, `std::cin >> std::ws` reads the whitespace at the beginning and throws it away. For example, if you have an input buffer of `\n \t Axel Kennedal\n`, the spaces, tab, and newline would be removed and the input buffer would be left with `Axel Kennedal\n`. The returned value of this is `std::cin`, which is what you pass in anyway, but now the buffer is short of the whitespace. Then, `std::getline` goes and reads until the newline like normal, but now it doesn't get any of that whitespace that existed at the beginning of the input. – chris Apr 10 '14 at 22:05

score 0 · Answer 2 · answered Apr 10 '14 at 16:42

You can just do this..

string password;
cout << "enter password:";
getline(cin, password);
cout << "The user inputted the password: " << password << endl;

Alternatvely, you can use cin to receive inputs. Now you can use cin.ignore.

string password;
cout << "enter password:";
cin >> password;
cin.clear();
cin.ignore(200, '\n');
cout << "The user inputted the password: " << password << endl;

It is good to use cin.clear() and cin.ignore() when you are receiving inputs using cin >>. However, if you are using getline(), it seems unnecessary to use cin.ignore().

Input being chopped off

2 Answers2