How to calculate the length of a string in C language?

In the C language, the strlen() function can be used to determine the length of a string. This function takes a string as a parameter and returns the length of the string. An example is shown below:

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

int main() {
    char str[50] = "Hello, World!";
    int len = strlen(str);
    printf("字符串的长度为：%d\n", len);
    return 0;
}

The output result is:

字符串的长度为：13

The strlen() function is defined in the string.h header file.