Easy. C programming question

spitso · May 12, 2011

Hi all

Just writing up some code, so far it all works perfectly until i accidentally enter a character (instead of an interger) for scanf.
It displays the menu over and over and over.....

Any ideas how i can get rid of this bug?
Im a beginner so i'd appreciate something as simplistic as possible.

Thankyou

attached is the code

Ian Rogers · May 12, 2011

There is a function in C called " isadigit() " so first call scanf for a character "%c" then check if its a digit then convert to an int (atoi());

Code:

char key;

if(isadigit(scanf("%c",key)))
   {
   process here;
   }
else
   dont;

something like this

Ian

OR.... just check that the scaned value is between 0 and 9.. (that's simpler)

BrownOut · May 12, 2011

The problem with "scanf" is that it leaves junk lying around in the buffer. If your menu is constantly being displayed, this might be the reason. Make a function like the one below, and call after the scanf line:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

...


void eat_junk(void) (
  int ch;

  while((ch = getchar()) != '\n') {
     if (ch < 0)
        exit(EXIT_FAILURE); //EOF!
  }
}

Find more information here : c - How to prevent the user from entering more data than the maximum limit? - Stack Overflow

spitso · May 12, 2011

thanks Ian

i tried checking the scanned value to see if its between 0 to 9, but if a character is press and it reloops.........its as if the programs skipping the scanf code and is just remembering what i had previously entered.

any ideas?

BrownOut · May 12, 2011

spitso said:
thanks Ian

any ideas?

Yes. See post #3.

spitso · May 12, 2011

Thanks for that

Im guessing the " ( " after (void) is mean't to be " { ".

also sorry for a million question but as i said im a beginner.
What would be the code to call this function, so i can put it after my scanf() statement?

thanks in advance

BrownOut · May 12, 2011

spitso said:
Thanks for that

Im guessing the " ( " after (void) is mean't to be " { ".

That's correct.

What would be the code to call this function, so i can put it after my scanf() statement?

scanf(.....);
eat_junk();
....

You can get some of answers from the web page I linked.

spitso · May 12, 2011

PERFECT!!!!!!!

Cheers boys, works all good now

Thanks!

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