Question

The problem I have is that I want to disable the user the possibility of putting character instead of number inside my program and optionally printing the message “it is disabled”. It should ask for the value of the same variable. I tried to do this using this:

scanf(" %[0-9]d",&x);

and this:

else
       result = scanf("%*s");

but it still does not work. What should I look for? I’ve searched internet, but I’ve only found solutions for C++ in which cin was used and unfortunately it does not work in C at all.

Answer 1

You can try something like this:

char c[SIZE];
int i;    

// While the string is not a number
while(fgets(c, SIZE , stdin) && !isAllDigit(c));  

where isAllDigit is:

int isAllDigit(char *c){
    int i;
    for(i = 0; c[i] != '\0' && c[i] != '\n'; i++) // Verify if each char is a digit
       if(!isdigit(c[i]))         // if it this char is not a digit
           return 0;              // return "false"

    return 1; // This means that the string is a number       
}