'\0' and printf() in C

Question

In an introductory course of C, I have learned that while storing the strings are stored with null character \0 at the end of it. But what if I wanted to print a string, say printf("hello") although I've found that that it doesn't end with \0 by following statement

printf("%d", printf("hello"));  Output: 5 

but this seem to be inconsistent, as far I know that variable like strings get stored in main memory and I guess while printing something it might also be stored in main memory, then why the difference?

Answer 1

The null byte marks the end of a string. It isn't counted in the length of the string and isn't printed when a string is printed with printf. Basically, the null byte tells functions that do string manipulation when to stop.

Where you will see a difference is if you create a char array initialized with a string. Using the sizeof operator will reflect the size of the array including the null byte. For example:

char str[] = "hello"; printf("len=%zu\n", strlen(str));     // prints 5 printf("size=%zu\n", sizeof(str));    // prints 6 

Answer 2

printf returns the number of the characters printed. '\0' is not printed - it just signals that the are no more chars in this string. It is not counted towards the string length as well

int main() {     char string[] = "hello";      printf("szieof(string) = %zu, strlen(string) = %zu\n", sizeof(string), strlen(string)); } 

https://godbolt.org/z/wYn33e

sizeof(string) = 6, strlen(string) = 5