In this C++ tutorial, you will learn how to get the first N characters in a given string, with example programs.

Get first N characters in String in C++

To get the first N characters from a given string in C++, you can use substr() method of string class.

C++ String - Get first N characters

1. Getting the first N characters in string using substr() method in C++

In the following program, we are given a string in str and an integer value in n. We have to get the first n characters from the string str using substr() method.

Steps

  1. Given an input string in str, and an integer value in n.
  2. Call the substr() method on the string str, and pass 0 for the first parameter, and n for the second parameter.
  3. The substr() method returns the substring in the string from the index position of 0 up to the index position of n.
  4. Store the returned value in a variable, say firstNChars, and use it as per your requirement.

Program

main.cpp

#include <iostream>
#include <string>
using namespace std;

int main() {
    // Given string
    string str = "Hello World!";
    // Number of first characters to extract
    int n = 3;

    // Use substr to get the first n characters
    string firstNChars = str.substr(0, n);

    cout << "First " << n << " characters: " << firstNChars << endl;

    return 0;
}

Output

First 3 characters: Hel

Now, let us try with another value of n, say 7, and get the first n characters in the string.

main.cpp

#include <iostream>
#include <string>
using namespace std;

int main() {
    // Given string
    string str = "Hello World!";
    // Number of first characters to extract
    int n = 7;

    // Use substr to get the first n characters
    string firstNChars = str.substr(0, n);

    cout << "First " << n << " characters: " << firstNChars << endl;

    return 0;
}

Output

First 7 characters: Hello W

Conclusion

In this C++ Tutorial, we learned how to get the first n characters in a string using string substr() method, with examples.