Simple program adding "D" to output

Question

I have a very simple program that just prints the number of newlines as an integer and I get a "D" after every number.

Sample input:
d [enter]
e [enter]
f [enter]
Ctrl-D [enter]

Sample output:
3D

What am I doing wrong?

This is verbatim from The C Programming Language 2nd edition, pg. 19:

#include <stdio.h>

main()  
{  
    int c, nl;  
    nl = 0;

    while ((c = getchar()) != EOF)  
        if (c == '\n')  
            ++nl;  
    printf("%d\n", nl);  
}

Answer 1

I think the D comes from the Ctrl D. The console outputs ^D as its standard echo logic, prior to passing the corresponding char (or rather here lack of char, i.e. EOF status) to getchar(), however, and rightfully, not sending a cr/lf. The C program then sends its 3, et voila...

Try the program by typing more than 9 CR before exiting and the problem should "go away", i.e. not show.

Answer 2

This works fine for me with GCC, whether I pipe in input or manually type it in and finish with ^D.

$ ./a.out
1
2
3
3
$ echo -ne "1\n2\n3\n" | ./a.out
3

It's probably like @mjv said, and the console is echoing the D back to you -- you're on Windows, right? I think that's normal for the Windows console.

Answer 3

Change the print line to this:

printf("\n%d\n", nl);

Then you'll see that when you hit ctrl-d, you get "^D" on the line. Only since you didn't press ctrl-D followed by Enter, then it's not on a newline in your original program. Not all systems will echo ctrl-d back to you, but it does on OS-X for example. So it ends up messing up the output if you print a one-digit number. You'll have to work around it.