How do you limit the maximum amount of characters in user input in C++?

Question

I want it so that when the user inputs more than 5 characters, something will happen, instead of just skipping the rest.

In this code, if you type in more than 5 characters, it will only show the first 5 characters. I want to put an "if" statement here that if the user inputs more than 5 characters, it will show an error or something, and not just show the first 5 characters.

#include <iostream>
#include <iomanip>

int main()
{
using namespace std;
string nationname;
int maxchar = 5;
cout << "What is the name of your nation?\n";

cin >> setw(maxchar) >> nationname;

cout << "The name of your nation is " << nationname;
cin.ignore();

return 0;
}

Thanks!

jamesdlin · Accepted Answer · 2013-04-22T18:27:54.537

3

You could read the string in its entirety first and then validate it:

int main()
{
    using namespace std;

    const int maxchar = 5;
    string nationname;

    cout << "What is the name of your nation?" << endl;

    cin >> nationname;

    if (nationname.size() > maxchar)
    {
       err << "The input is too long." << endl;
       return 1;
    }

    // ...
}

Incidentally, you should use std::endl with your prompt and not just \n; you want to make sure that the prompt is flushed to the screen before you start waiting for user input. (Edit: As Loki Astari points out in the comments, this part's not actually necessary.)

edited Apr 22 '13 at 18:27

answered Apr 21 '13 at 18:48

jamesdlin

81,374
13
159
204

Thanks! Do you know how to loop it back to the "cout" after it says the error? – Leroterr1 Apr 21 '13 at 18:58
`do{cin >> nationname; if(nationname.size() > maxchar) /*output*/ }while( nationname.size() > maxchar);` – Zaiborg Apr 21 '13 at 19:03
Thanks! jamesdlin and Zaiborg. – Leroterr1 Apr 21 '13 at 19:21
Actually there is no need to use std::endl. The standard streams (std::cin and std::cout) are synced so that all output to std::cout is flushed before user input is retrieved. – Martin York Apr 21 '13 at 22:57

score 0 · Answer 2 · answered Sep 26 '14 at 06:18

**

#include <iostream>
#include <iomanip>
#include<string>
#include <conio.h>
int main() {
    using namespace std;
    const int maxchar = 6;
    string nationname;
    cout << "What is the name of your nation?" << endl;
    getline(cin, nationname);
    if (nationname.size() > maxchar)
    {
       cout << "The input is too Short." << endl;
    }   getch(); 
    return 0; 
}

**

you can use this code. This is working perfectly without any errors. Also you can convert this into minimum character enter making few changes.

How do you limit the maximum amount of characters in user input in C++?

2 Answers2

Linked