Force input to be positive numbers only with error handling in C

Question

I have a trivial question to ask. My program should take postive integers only. If there is anything illegal, the user should be prompted to input a number again.

Th

Answer 1

i have solved your program. Try the following program in Turbo C++:

#include<stdio.h>
#include<conio.h>
main()
{
    char n[2],ni;
    clrscr();
    GET:
    printf("Enter positive number: ");
    scanf("%s",&n);
    if(atoi(n)>0)
    {
        printf("You have entered ");
        ni=atoi(n);
        printf("%d",ni);
    }
    else if(atoi(n)<=0)
    {
        printf("Wrong choice\n");
        goto GET;
    }
    else
    {
        printf("Wrong choice\n");
        goto GET;
    }
    getch();
}

Answer 2

Use fgets to read a whole line into a buffer. If you only want to process the first character, you can just ignore the rest. Something along the lines of:

char buf[MAX_LINE_LEN];
if (fgets(buf, MAX_LINE_LEN, stdin))
{
    char a = buf[0];
    /* Do handling... */
}
else
{
    /* error */
}

Coded in browser, may contain traces of error.

Answer 3

while(num<=0){
  printf("Please Enter positive integer: ");
  while(((reads = scanf("%d%c", &num, &a)) != 2 && reads != EOF) || a != '\n' ){
    printf("Please Enter positive integer: ");
    while(getchar() != '\n');
  }
}