When working with strings in C++ cstring strcmp() , it is essential to understand the core functions provided for handling string comparisons. One of the most commonly used functions in C is strcmp(), which is also available in C++ through the Cstring library. This function is crucial when comparing two null-terminated C-style strings (character arrays). In this post, we’ll explore the strcmp() function in detail, its syntax, and its use cases.

What is strcmp()?
strcmp() stands for "string compare" and is a C function that compares two null-terminated strings lexicographically (character by character). This function returns an integer value based on the comparison result:

0 if the strings are equal.
A negative value if the first string is lexicographically less than the second.
A positive value if the first string is lexicographically greater than the second.
This function is defined in the Cstring library (<cstring> in C++). While C++ offers more flexible string handling with std::string, strcmp() remains a useful tool when working with C-style strings.

Syntax of strcmp()
The syntax of strcmp() is as follows:

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int strcmp(const char* str1, const char* str2);
Where:

str1 is the first C-style string.
str2 is the second C-style string to compare with.
How strcmp() Works
The strcmp() function compares the strings character by character. It starts with the first character of both strings and continues comparing the characters until:

A difference is found.
It reaches the end of one or both strings (i.e., the null character '\0').
If a character difference is found, the function returns the difference in their ASCII values. If no difference is found and both strings are of equal length, it returns 0 indicating the strings are identical.

Example Usage
Here's an example demonstrating how strcmp() works in a C++ program:

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include <iostream>

include <cstring> // For strcmp()

int main() {
const char* string1 = "Hello";
const char* string2 = "World";
const char* string3 = "Hello";

// Comparing string1 and string2
int result1 = strcmp(string1, string2);
if (result1 == 0)
    std::cout << "string1 and string2 are equal.\n";
else if (result1 < 0)
    std::cout << "string1 is lexicographically less than string2.\n";
else
    std::cout << "string1 is lexicographically greater than string2.\n";

// Comparing string1 and string3
int result2 = strcmp(string1, string3);
if (result2 == 0)
    std::cout << "string1 and string3 are equal.\n";
else
    std::cout << "string1 and string3 are not equal.\n";

return 0;

}
Output:

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string1 is lexicographically less than string2.
string1 and string3 are equal.
Important Points to Remember
Case Sensitivity: strcmp() is case-sensitive. The comparison differentiates between uppercase and lowercase letters. For example, 'A' is considered less than 'a'.
Null-terminated Strings: strcmp() expects C-style strings (null-terminated). It does not work with std::string objects, though you can convert std::string to C-style strings using the c_str() method.
Performance: strcmp() compares strings character by character, making it an O(n) operation, where n is the length of the strings being compared.
Alternatives in C++
While strcmp() is widely used in C, C++ offers alternatives like std::string's compare() method, which is safer and more convenient for modern C++ development:

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std::string str1 = "Hello";
std::string str2 = "World";
if (str1.compare(str2) == 0) {
std::cout << "The strings are equal." << std::endl;
} else {
std::cout << "The strings are not equal." << std::endl;
}
Conclusion
The strcmp() function is an essential part of working with C-style strings in C++. Understanding how it works and how to use it correctly can greatly improve your ability to handle string comparisons in your C++ programs. Whether you're dealing with legacy C code or need efficient comparisons, strcmp() remains a valuable tool in your programming toolkit.
More Visit- https://docs.vultr.com/cpp/standard-library/cstring/strcmp