5 replies to this topic

[Max.89]

I have a problem with the function scanf from the stdio.h library.
For example if I write something like this:

char choice;

while(choice != ' ')
{
  printf("Insert a char (space to finish):");
  scanf("%c",&choice);
  ...
}

The sentence in printf() is printed in output twice.
It only happens with %c and not with %d inside loops(both while and for).
Why?
Thanks in advance.

Edited by WingedPanther, 01 January 2009 - 06:19 AM.
add code tags (the # button)

[WingedPanther]

Without seeing the rest of your code, it's hard to say. You shouldn't be using %d, which suggests there is a problem elsewhere in the code.

[Max.89]

I don't know if the rest of the code matters because it's not the first time I have this problem.
Every single program in which I used %c with printf or scanf inside a loop printed the text twice.I always avoided the problem using %d instead of %c but now I need to use characters.
This is a function of my code:

void printList(listElementType *listPtr)

{

  

  while(listPtr != NULL)

  {

    printf("--->%c",listPtr->elem);

    listPtr = listPtr->nextPtr;

  }

}

This is the output for a single printf
--->char--->char

Maybe in every program I made I did the same mistake in some part of the source code,but if it was a logical error it should have showed the double text output also for %d and not only for %c.

[Phoenixz]

I dunno if this is right or not, but just an attempt of helping you.. :P If you used a previous scanf did you use fflush(stdin); also to clear it?

[Max.89]

You are right I didn't use fflush function...
Now it works.
Thanks.

[dargueta]

It shouldn't. fflush() is only defined for output streams. Even if it does work for you on your computer, there is no guarantee it'll work anywhere else.