用户验证仅适用于正整数

Question

I'm writing a program that only accepts a positive int greater than 0 and nothing else. The problem is when the user enters a decimal number, how do I validate that if weight is a decimal number I ask the user again.

printf("Please enter your weight in pounds: ");
scanf("%d", &weight);

while(weight <= 0)
{
    printf("Invalid weight! Please enter a positive number: ");
    scanf("%d", &weight);
}
printf("Your weight is %d\n",weight);

Answer 1

Use fgets to get the data entered into a string buffer, check that the string only contains numbers, and only then use sscanf or atoi to convert the string to a number. Finally check that the number is larger than 0.

Answer 2

this is the algorithm

->take an array of characters
->read the number in array
->the first character should be a '+' or a '0 - 9'
->the remaining characters should be '0 - 9'

that's it is a positive number

if you want to convert it into number use atoi function in standard library

http://www.tutorialspoint.com/c_standard_library/c_function_atoi.htm

Answer 3

This is a solution (untested) :

int weight = 0, c;
printf("Please enter your weight in pounds: ");

for(;;) { /* Infinite loop */
  if(((c = scanf("%d", &weight)) == 1 || c == EOF) && weight > 0 && ((c = getchar()) == EOF || c == '\n'))
  /* If the user enters a valid integer and it is a positive number and if the next character is either EOF or '\n' */
    break; /* Get out of the loop */

  /* If the execution reaches here, something invalid was entered */

  printf("Invalid weight! Please enter a positive number: ");
  while((c = getchar()) != EOF && c != '\n'); /* Clear the stdin */
}

if(c != EOF)
  printf("Your weight is %d\n",weight);