strlen() function in c

The strlen() function in C is used to find the length of a null-terminated string, which is the number of characters in the string excluding the null-terminator (\0).

Here’s how it works:

Syntax:

size_t strlen(const char *str);

• str: This is the pointer to the null-terminated string whose length is to be calculated.
• The return value is of type size_t (an unsigned integer), which represents the length of the string in characters, excluding the null terminator.

Example:

#include <stdio.h>
#include <string.h>

int main() {
    char str[] = "Hello, world!";
    
    // Using strlen to get the length of the string
    size_t length = strlen(str);
    
    printf("The length of the string is: %zu\n", length);
    
    return 0;
}

Explanation:

• In this example, strlen(str) returns the length of the string "Hello, world!", which is 13.
• Note that strlen does not count the null terminator (\0) in the string’s length.

Important Points:

1. Null-terminated strings: The string must be null-terminated. If it’s not, strlen() may lead to undefined behavior.
2. Time complexity: The time complexity of strlen() is O(n), where n is the length of the string, because it needs to iterate through the entire string until it finds the null terminator.

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