Printf a buffer of char with length in C

Question

I have a buffer which I receive through a serial port. When I receive a certain character, I know a full line has arrived, and I want to print it with printf method. But each line has a different length value, and when I just go with:

printf("%s", buffer);

I'm printing the line plus additional chars belonging to the former line (if it was longer than the current one).

I read here that it is possible, at least in C++, to tell how much chars you want to read given a %s, but it has no examples and I don't know how to do it in C. Any help?

I think I have three solutions:

• printing char by char with a for loop
• using the termination character
• or using .*

QUESTION IS: Which one is faster? Because I'm working on a microchip PIC and I want it to happen as fast as possible

Answer 1

You can either add a null character after your termination character, and your printf will work, or you can add a '.*' in your printf statement and provide the length

printf("%.*s",len,buf);

In C++ you would probably use the std::string and the std::cout instead, like this:

std::cout << std::string(buf,len);

If all you want is the fastest speed and no formatting -- then use

fwrite(buf,1,len,stdout);