[Klug-general] C problem with delay and erase in Ubuntu terminal & Code::Blocks.

[Daniel Ellis]

Hi Malcom, welcome to the group.

After trying out your example, I noticed the same behavior which I
didn't expect.  Then I found:-

http://stackoverflow.com/questions/1716296/why-does-printf-not-flush-after-the-call-unless-a-newline-is-in-the-format-strin

So fflush is what you need here, for example:-

printf("Hello world!");
fflush(stdout);

Regards,
Dan Ellis

On 31 July 2012 21:36, JACKSON MALCOM <malcom.jackson at ntlworld.com> wrote:
>
> Hello all,
> I have just joined KLUG, being very keen on learning about  Ubuntu and
> Linux.
>
> I have run up against a problem whilst  working through Ivor Hortons book
> Beginning C, 3rd edition, using Terminal and CodeBlocks 10.04, on 11.04
> 'Natty Narwhal'.
> There have been a couple of problems such as getchar and buffering that I
> have managed to get solved on line, but now on Page 180 I have hit a brick
> wall.
>
> There is a sample program called Simple Simon.
>
> Simple Simon is a memory game that posts a sequence of numbers on the screen
> for you to memorise. After 1 second the numbers are erased, and you have to
> key in what you remember, and hope that you have remembered correctly.
>
> I have not been able to get the program working on terminal or through code
> blocks, despite several days of trying to find out what is wrong.
> A couple of days ago I decided to start from scratch and write my own
> version of the program, building up a bit at a time and perhaps find out why
> the original program won't work for me.
>
> The problem I have  is with the following piece of code which should give a
> 1 second delay and then erase the previously printed sequence of numbers.
> (This code works OK on XP and Vista):-
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <time.h>
>
>  int main()
>    {
>      long now = 0;
>      printf("Hello world!");
>      now = clock();
>
>      for(;clock() - now<CLOCKS_PER_SEC;  );       /*After 1 second delay
> this "*/
>          printf("\r");
> /*"code should erase  the string "Hello world!" */
>          printf(" ");
>
> return 0;
> }
>
> I have tried all sorts of delay methods, but they all end up not doing what
> I want to do.
> Instead of writing Hello world! on the screen and erasing it after 1 second,
> the screen comes up and after 1 second Hello world! is printed and erased at
> the same instant.
> I put a break in before the delay, and can see Hello world! is indeed
> printed.
>
> On XP and Vista this program works correctly.
>
> I have checked through the man pages, but don't yet know enough to know if I
> have found an answer or not. Nothing I have tried works, so would be
> mightily obliged if some one will let me know what to do to get this
> working.
> Many thanks,
> Malcolm Jackson.
>
> --
> Hello Ubuntu ...... Goodbye  Microsoft.
> malcom.jackson at ntlworld.com
>
> _______________________________________________
> Kent mailing list
> Kent at mailman.lug.org.uk
> https://mailman.lug.org.uk/mailman/listinfo/kent