Reading characters into a limited buffer size

Reading characters into a limited buffer size

I'm designing a shell in C. It takes in characters and reads them into a
buffer of limited size (in this case 64). If the user enters more than 64
characters, it rejects the entire input string, warns the user that they
entered too many characters, and starts over. If the user hits ctrl-D,
which is an end-of-file, the program exits.
So my solution is this: make the actual underlying buffer 65 characters to
accomodate for the newline character. If the final character is not a
newline, then the user hit ctrl-D, so the program exits. If the buffer is
filled (i.e. it contains 65 characters) and the final one isn't a newline,
the program assumes that too many characters were given, so it goes into a
loop and continually reads input into the buffer until it the buffer read
in ends with a newline (in which case it warns the user of the limit and
starts over), or it's cut short without ending in a newline (in which case
the program terminates).
My question is, how can I handle the case where the user enters exactly 65
characters (or some integer multiple of 65), and then hits ctrl-D? As the
program currently stands, when the buffer is filled and doesn't end in a
newline, it assumes there was an overflow, but in this case I would like
the program to terminate. How can I make the program terminate upon
receiving a scalar multiple of 65 characters and then a ctrl-D?
#include <string.h>
#include <unistd.h>
#define BUFSIZE ( 65 )
int main( int argc, char* argv[] ) {
char* prompt = "myshell->";
char* tooMany = "Max characters (64) exceeded.\n";
int numInput;
int done = 0;
char input[ BUFSIZE ];
while( !done ) {
int cont = 0;
write( STDOUT_FILENO, prompt, strlen( prompt ) );
numInput = read( STDIN_FILENO, input, BUFSIZE );
if( input[ numInput - 1 ] == '\n' ) {
cont = 1;
} else {
if( numInput != BUFSIZE ) {
done = 1;
write( STDOUT_FILENO, "\n", strlen( "\n" ) );
} else {
int spill = 1;
while( spill ) {
numInput = read( STDIN_FILENO, input, BUFSIZE );
if( input[ numInput - 1 ] == '\n' ) {
spill = 0;
write( STDOUT_FILENO, tooMany, strlen( tooMany ) );
} else {
if( numInput != BUFSIZE ) {
spill = 0;
done = 1;
write( STDOUT_FILENO, "\n", strlen( "\n" ) );
}
}
}
}
}
/*done ingesting input. Now do something with it...*/
if( cont ) {
write( STDOUT_FILENO, input, numInput );
}
}
return 0;
}