UTF-8 string size in bytes

Question

I need to determine the length of UTF-8 string in bytes in C. How to do it correctly? As I know, in UTF-8 terminal symbol has 1-byte size. Can I use strlen function for this?

Answer 1

Can I use strlen function for this?

Yes, strlen gives you the number of bytes before the first '\0' character, so

strlen(utf8) + 1

is the number of bytes in utf8 including the 0-terminator, since no character other than '\0' contains a 0 byte in UTF-8.

Of course, that only works if utf8 is actually UTF-8 encoded, otherwise you need to convert it to UTF-8 first.