I just don't spend enough time "tinkering" with *nix. Anyhow when I
read from an unbuffered input and type something in, I get two prompts
after I hit return.

m-net%% more tty.c
#include

int main(void)
{
char c;

return(read(0, &c, 1) == 1) ? (unsigned char)c : EOF;

return 0;
}
m-net%% ./tty
c
m-net%%
m-net%%

Now when I buffer the input, and type something in, I only get one
prompt after I hit return.

m-net%% more tty2.c
#include