Tutorials

C++ String strncmp() Function

Posted in C++ Tutorial

Updated on Nov 19, 2024

By Mari Selvan

👁️ 351 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In C++ programming, comparing strings is a common operation, and the C++ Standard Library provides the strncmp() function for this purpose.

This function allows you to compare substrings of two strings up to a specified length.

In this tutorial, we'll explore the usage and functionality of the strncmp() function in C++.

💡 Syntax

The signature of the strncmp() function is as follows:

Syntax

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int strncmp(const char *str1, const char *str2, size_t n);

This function compares the first n characters of two C-style strings (str1 and str2).

📄 Example

Let's delve into an example to illustrate how the strncmp() function works.

strncmp.cpp

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#include <iostream>
#include <cstring>

int main() {
  const char * str1 = "Hello, World!";
  const char * str2 = "Hello, C++!";

  // Compare the first 5 characters case-sensitively
  int result = strncmp(str1, str2, 5);

  // Output the result
  if (result == 0) {
    std::cout << "The substrings are equal.\n";
  } else {
    std::cout << "The substrings are not equal.\n";
  }

  return 0;
}

💻 Output

Output

The substrings are equal.

🧠 How the Program Works

In this example, the strncmp() function compares the first 5 characters of the strings "Hello, World!" and "Hello, C++!" and prints the result.

↩️ Return Value

The strncmp() function returns an integer less than, equal to, or greater than zero if the first n characters of str1 are found, respectively, to be less than, to match, or be greater than the first n characters of str2.

📚 Common Use Cases

The strncmp() function is useful when you need to compare substrings of two strings up to a specific length. It's commonly employed in scenarios where you want to check the equality of a portion of two strings.

📝 Notes

The comparison is case-sensitive. If you need a case-insensitive comparison, consider using strncasecmp() in POSIX systems or a custom case-insensitive comparison function.

🎢 Optimization

The strncmp() function is optimized for efficient substring comparison. Ensure that the specified length n does not exceed the length of the shorter string to avoid undefined behavior.

🎉 Conclusion

The strncmp() function in C++ is a versatile tool for comparing substrings of two strings up to a specified length. It provides a standardized and efficient way to perform substring comparisons, enhancing the flexibility of your code.

Feel free to experiment with different strings and explore the behavior of the strncmp() function in various scenarios. Happy coding!