Need help with getline. Unable to insert strings.

nikp · #1 01-Dec-2005, 13:05

Hello everyone,

I wrote a small program in order to find out how getline works but out of nowhere, I ended up trying to understand what happens and it is not working properly. Till now I found out nothing. Could you please help me?

Below is the code.

CPP / C++ / C Code:

#include <iostream>
#include <string>

using namespace std;

int main() {
	int a, b;
	string s1, s2;

	for(int i = 0; i < 4; i++) {
		cout << "a: ";
		cin >> a;
		
		cout << "s1: ";
		getline(cin, s1);
		
		cout << "b: ";
		cin >> b;
		
		cout << "s2: ";
		getline(cin, s2);
	}

	return 0;
}

And here is what happens when I run the program.

a: (waits value, I insert 4)
s1: b: (waits value)
Why does it not request from the user to insert a value for s1??
It goes directly to b:.

The same happens with b and s2 until the loop ends.

Any ideas?
Thank you

Sokar · #2 01-Dec-2005, 14:44

It is because you are mixing cin and getline. Long story short cin leaves the '\n' in the stream and this is the delimiter for getline so getline finds the '\n' and stops reading. Just add cin.ignore();(ignore will skip 1 character with no arguments) before getline.

CPP / C++ / C Code:

#include <iostream>
#include <string>

using namespace std;

int main() {
	int a, b;
	string s1, s2;

	for(int i = 0; i < 4; i++) 
	{
		cout << "a: ";
		cin >> a;
		
		cout << "s1: ";
		cin.ignore();
		getline(cin, s1);
		
		cout << "b: ";
		cin >> b;
		
		cout << "s2: ";
		cin.ignore();
		getline(cin, s2);
	}

	return 0;
}

WaltP · #3 01-Dec-2005, 17:51

To add little info to Sokar's excellent description:

CPP / C++ / C Code:

cout << "a: ";
cin >> a;

Enter: 56<enter> -- 3 characters in buffer.
cin: 5 & 6 read, <enter> is not a digit
Buffer: <enter>

CPP / C++ / C Code:

cout << "s1: ";
getline(cin, s1);

Enter: nothing (<enter> is still in buffer).
cin: <enter> read
Buffer: empty

CPP / C++ / C Code:

cout << "b: ";
cin >> b;

Enter: 129<enter> -- 4 characters in buffer.
cin: 1 & 2 & 9 read, <enter> is not a digit
Buffer: <enter>

CPP / C++ / C Code:

cout << "s2: ";
getline(cin, s2);

Enter: nothing
cin: <enter> read
Buffer: empty

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Rate This Thread
Rate This Thread:

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Strings tripping me up once more	Elsydeon	C++ Forum	5	04-Dec-2005 18:41
need help - questions about strings	Benayoun	C Programming Language	6	24-Jan-2005 03:15
array of pointers to strings	mirizar	C++ Forum	5	21-Jan-2005 11:24
I am reviewing Arrays and need help converting some strings to arrays	jenmaz	C Programming Language	22	23-Nov-2004 00:26
urgent help needed :c + mysql insert	jack	C Programming Language	1	13-Apr-2004 22:16

Need help with getline. Unable to insert strings.

Re: Need help with getline. Unable to insert strings.

Re: Need help with getline. Unable to insert strings.