Thread: getchar()

I've got a simple program which asks users for a number 1- 10 and then checks if its a digit or not. At the end I want to prompt the user if they want to continue or exit
and if they want to continue I want to go back to the top.

I put the user's data in an array called c[i] for each character using getchar() and a
loop.

I've read that to clear the input buffer I need to do something like:

while( (d = getchar()) && d != '\n' && d != EOF)
d = getchar;

Problem, input buffer doesn't get cleared. If it put another clear buffer at the top then the user must hit enter but they don't know that.


insert

Code:

int main()
{
  
    
    int i, j;
    char c[100];
    int lengthOfInput = 0;
    char d = 0;
    
    j = 0;
    
    while ( j == 0 )
    {

    // initialize array
    
    for (i = 0; i <= 100; ++i)
    {
        c[i] = '\0';
    }
    
    /* Ask for input */
    printf("Enter a number from 1-10.\n");
    for (i = 0; c[i - 1] != '\n'; ++i) {
        c[i] = getchar();
        lengthOfInput += 1;
    }
    
    
    /* Take care of 10 */
    if (((lengthOfInput-1) == 2) && (c[0] == '1') && (c[1] == '0'))
        printf("\'10 divided by 25 is %.1f'\n", 10.0/25.0);
    else if ((lengthOfInput-1) == 1)
    {   
        if (isdigit(c[0]))
        {
            switch(c[0])
            {
                    
                case '4':
                    printf("You chose %c. 4 + 10 is %d.\n", c[0], 4 + 10);
                    break;
                default:
                    printf("You chose %c.\n", c[0]);
                    break;
            }
        }
        else
        {
            printf("Not a valid digit\n");
        }
    }
    else
        printf("Not a valid digit 2.\n");
        
        
        printf("Hit 0 to continue\n");
        
        while ((d = getchar()) && d != '\n' && d != EOF) {
            d = getchar();
            if (d != '0') 
                j = 1;
        }
    }
    
    
}

Code:

// wrong
while( (c = getchar()) && c != '\n' && c != EOF)
c = getchar;


// better
while( (c = getchar()) && c != '\n' && c != EOF)
c = getchar();

You need to watch your compiler's warnings and errors... it should have complained about the missing brackets.


And here's a little trick for you... If you use scanf() instead of getchar(), you can tell it to ignore "whitespace" (spaces, tabs, \n, etc) in the buffer like this...

Code:

scanf (" %c", &charvar);

Note the space between the " and % ...