C strlen Function

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Function signature: size_t strlen(const char *str);

Function description: The strlen() function computes the length of the null-terminated string str.

Function return value: The length of the string, not including the null terminator.

Funcion computational cost: generally O(n)

Library: string.h

Function example:

#include <stdio.h> 
#include <string.h>  
int main() {     
	char str1[] = "Hello, world!";     
	char str2[] = "";     
	char *str3 = "This is a test string.";     
	
	size_t len1 = strlen(str1);     
	size_t len2 = strlen(str2);     
	size_t len3 = strlen(str3);      
	
	printf("Length of str1: %zu\n", len1); 
	printf("Length of str2: %zu\n", len2); 

The output is:

Length of str1: 13 
Length of str2: 0 
Length of str3: 22

In this example, we declare three strings: str1, str2, and str3. We then use strlen() to compute the length of each string and store the results in integer variables len1, len2, and len3. Finally, we print the length of each string using printf().

Funcion Computational Cost

The computational cost of strlen() is O(n), where n is the length of the input string, and increases linearly with the length of the string. However, the function is highly optimized for performance, so its execution time is usually negligible.