// return -1 on EOF

int GetPositiveNumber(const char *prompt, const char *reprompt) {

  char buf[100];

  fputs(prompt, stdout);

  fflush(stdout);

  while (fgets(buf, sizeof buf, stdin)) [

    int value;

    if (sscanf(buf, "%d", &value) == 1 && value > 0) {

      return value;

    }

    fputs(reprompt, stdout);

    fflush(stdout);

  }

  return -1;

}

​

// Usage

int TktAdult = GetPositiveNumber(

    "\nEnter amount of adult tickets:" , 

    "\nPlease enter a positive number!");

if (TktAdult < 0) Handle_End_of_File();

else Success(TktAdult);

#include <stdio.h>

int main()

{

    int num=1;

    int numberRead = 0;

    do{

        printf("Enter a number: ");

        numberRead = scanf("%d",&num);

        while(numberRead != 1){

            printf("That is not a number.\n");

           scanf("%*[^\n]");  //or fflush(stdin);

            printf("Enter a number: ");

            numberRead = scanf("%d",&num);

        }

        printf("You entered %d\n",num);

    }while(num != 0);

​

    return 0;

}

​

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

​

int main()

{

    int i=0, isFloat=0, isChar=0;

    int intNum=0;

    float floatNum=0;

    char str[100];

    printf("Enter a number:");

    scanf("%s",str); // no &

    for(i=0; i<strlen(str); ++i)

    {

        // if not 0-9

        if(!((str[i]>='0')&&(str[i]<='9')))

        {

            if(str[i]=='.')

            {

                isFloat ++;

            }

            else{

                isChar ++;

            }

        }

    }

     if(isChar || isFloat > 1)

     {

         printf("This is not a number.");

     }

     else if(isFloat == 1)

     {

         printf("This is a float.");

         floatNum=atof(str);

         printf("input as float %.2f\n",floatNum);

     }

     else {

         printf("This is a valid int.\n");

         intNum=atoi(str);

         printf("input as int %d\n",intNum);

     }

    return 0;

}