How to Read Entire Lines of Input Including Spaces with C \'s `cin`?

C "cin" Only Reads the First Word

In C , the input stream operator >> typically reads a single word from an input source such as the keyboard. This can be problematic when attempting to read a string that contains spaces, as only the first word will be captured. This issue can be encountered while working with character arrays.

Consider the following code:

<code class="c++">#include <iostream.h>
#include <conio.h>

class String
{
    char str[100];
    public:
    void input()
    {
        cout << "Enter string :";
        cin >> str;
    }

    void display()
    {
        cout << str;
    }
};

int main()
{
     String s;
     s.input();
     s.display();
     return 0;
}

When running this code in Turbo C 4.5, only the first word of a string is displayed. This is because cin >> str reads only one word into the str character array. To read a complete line of input, including spaces, an alternate approach is required.

One option is to use the getline() function:

<code class="c++">#include <iostream>
#include <string>

using namespace std;

int main()
{
    string s;
    cout << "Enter string :";
    getline(cin, s);
    cout << s;
    return 0;
}</code>

This code will read the entire line of input, including spaces, into the s string. getline() can also be used to read into character arrays:

<code class="c++">#include <iostream.h>
#include <conio.h>

int main()
{
    char str[100];
    cout << "Enter string :";
    cin.getline(str, sizeof str);
    cout << str;
    return 0;
}

Alternatively, if you prefer to use the >> operator, you can modify the code as follows:

<code class="c++">#include <iostream.h>
#include <conio.h>

class String
{
    char str[100];
    public:
    void input()
    {
        cout << "Enter string :";
        cin.getline(str, sizeof str);
    }

    void display()
    {
        cout << str;
    }
};

int main()
{
     String s;
     s.input();
     s.display();
     return 0;
}</code>

With these modifications, the code will correctly read and display the entire input string.

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