How do you determine the length of a string in the C language?

In C language, the strlen() function from the standard library can be used to calculate the length of a string. This function is located in the string.h header file. strlen() takes a string as a parameter and returns the length of the string, excluding the null character ‘\0’ at the end of the string.

Here is an example of using the strlen() function:

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

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

The output is: the length of the string is 13.