Tutorials

C++ String strlen() Function

Posted in C++ Tutorial

Updated on Nov 19, 2024

By Mari Selvan

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4 mins

1 Comment

Photo Credit to CodeToFun

Introduction

In C++ programming, strings are commonly used for storing and manipulating text.

The strlen() function is a fundamental part of the C++ Standard Library, and it allows you to determine the length of a C-style string.

In this tutorial, we'll explore the usage and functionality of the strlen() function.

Syntax

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

Syntax

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size_t strlen(const char *str);

This function takes a pointer to a null-terminated C-style string (const char* str) and returns the length of the string.

Example

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

strlen.cpp

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#include <iostream>
#include <cstring>

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

  // Get the length of the string
  size_t length = strlen(str);

  // Output the result
  std::cout << "Length of the string: " << length << std::endl;

  return 0;
}

Output

Length of the string: 11

How the Program Works

In this example, the strlen() function is used to determine the length of the C-style string "Hello, C++!" and prints the result.

Return Value

The strlen() function returns the number of characters in the C-style string str before the null terminator.

Common Use Cases

The strlen() function is useful when you need to obtain the length of a C-style string dynamically during runtime. It's commonly used in scenarios where you want to iterate through the characters of a string or allocate memory based on the string's length.

Notes

Ensure that the C-style string passed to strlen() is null-terminated. Not doing so can result in undefined behavior.
For C++ std::string objects, you can use the size() member function or length() member function to get the length directly.

Optimization

The strlen() function is optimized for efficiency, but for performance-critical applications, consider caching the length of a string if it is used multiple times, rather than repeatedly calling strlen().

Conclusion

The strlen() function in C++ is a straightforward yet powerful tool for obtaining the length of C-style strings. It plays a crucial role in string manipulation and memory allocation tasks.

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