Thread: Issue with scanf and char

  1. #1
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    Issue with scanf and char

    Hi,

    So I get this simple thing here, meant to get a number between 1 and 12. The problem is, in my program, if I enter a character, I get an infinite loop and I just can't find a way to fix it. Any idea?

    Code:
    int demanderposition1()
    {
    	int position1=1;
    	
    	do
    	{	
    		if(position1<=0 || position1>12)
    		{
    			printf("Erreur de saisie, veuillez recommencer.\n");
    		}
    		printf("Faites votre 1er choix de position entre 1 et 12 :");
    		fflush(stdin);
    		scanf("%d", &position1);
    	}while((position1<=0 || position1>12));
    
    
    	return position1;
    }

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    If you don't know that the input that comes in is going to agree with the pattern (in this case, if they are using a keyboard that has anything other than 0-9 on it), then scanf is not an appropriate choice. To get a line of input for further processing, use fgets with a character buffer. You can then attempt to read with sscanf, or if they typed in garbage, throw it away and try again.

  3. #3
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    And what if I know it's a keyboard with numbers from 0 to 9? :P

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    If you know that they're using a keyboard with only the 0123456789, then you don't have to worry about them pressing 'b'.

  5. #5
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    Well sorry, I meant a full keyboard that included too 0 to 9 ^^'

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    Then scanf is not an appropriate choice. Use fgets to read into a character buffer, and check the input to see if it's a number (using sscanf or strtol).

  7. #7
    and the hat of int overfl Salem's Avatar
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    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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