Date: Sat, 17 Jan 2015 21:01:04 +0000 From: "Montgomery-Smith, Stephen" <stephen@missouri.edu> To: less xss <less.xss@gmail.com>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: ctrl-d appends characters to output Message-ID: <54BACD8C.3050703@missouri.edu> In-Reply-To: <54BAC302.7050800@missouri.edu> References: <CAGcjGpP0t3%2BcJLRHS5Ggfjao9Vcy0xosAg2KqBWgVA_NtKoNgA@mail.gmail.com> <54BAC302.7050800@missouri.edu>
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On 01/17/2015 02:16 PM, Montgomery-Smith, Stephen wrote:
> On 01/17/2015 11:59 AM, less xss wrote:
>> I've searched around quite a bit with no luck on this matter. I currentl=
y
>> have an issue where I send EOF (ctrl-d) to some simple K&R2 exercises an=
d
>> the terminal returns the D character appended to my data when EOF is sen=
t.
>> I wish to prevent any and all extra characters from being appended and I
>> would also like to understand why it's happening. The following code
>> is an example exercise from K&R2 that yield said problem.
>>
>> #include <stdio.h>
>>
>> int main() {
>> double nc;
>>
>> for (nc =3D 0; getchar() !=3D EOF; ++nc) {
>> ; /* syntactic null statement */
>> }
>>
>> printf("%.0f\n", nc);
>> }
>>
>> $ ./a.out
>> 0D
>> $
>=20
> I did a bit of experimenting with this issue. First, I cannot reproduce
> it on my Linux box. Second, this simpler program does the same thing:
>=20
> #include <stdio.h>
>=20
> int main() {
>=20
> while (getchar() !=3D EOF) {
> ; /* syntactic null statement */
> }
>=20
> printf("\n");
> }
>=20
> In this case I get:
>=20
> % ./a.out
> ^D
> %
>=20
> However, if I remove that last printf statement, then no ^D is displayed.
>=20
> Considering the inconsistent nature of when this ^D appears, I would
> prefer to call it a bug than a feature. But it must have been put there
> by design.
OK, that last printf is NOT responsible for the ^D. It is just that the
prompt wipes it out. Try this code:
#include <stdio.h>
#include <unistd.h>
int main() {
while (getchar() !=3D EOF) {
; /* syntactic null statement */
}
sleep(10);
}
Then the ^D shows until the prompt appears 10 seconds later.
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