Thread: This odd program works? Reading string and checking if integer. Need warning explaind

Hey folks, wrote this program to check if a string is an integer. It checks for + or - sign at the front of it, but it spat out some errors.

I think I broke it.

Here is the code:

Code:

#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>

int getInteger(char*);

int main(void) {
   char str[99];
   int x;
   
   printf("Enter an integer: ");
   gets(str);   
   char *moo = str;
   
   if (getInteger(str) == 1) {
      printf("The number you entered is not a valid integer.");
      }
   else {
      x = atoi(str);
      printf("the number you entered is %d", x);
      }

return 0;
}

int getInteger(char *moo) {
   
   if (*moo == '-' || *moo == '+') {
      ++moo;
      printf("Positive or negative sign detected.\n");
      }
   
   if (*moo == NULL) {
      return 1;
      printf("You messed up.\n");
      }
   while (*moo) {
      if (!isdigit(*moo)) {
         printf("You are not a digit!\n");
         return 1;
         }
      else {
         ++moo;
         }
      }
   return 0;
}

Here are the warnings I get:

warning: unused variable 'moo'

Code:

char *moo = str;

in function 'getInteger'
warning: comparison between pointer and integer

Code:

if (*moo == NULL) {

Can you guys help me fix these errors?

TIA!

1; remove that line

Code:

char *moo = str;

moo is never used

2: NULL is defined as a pointer type. You want to compare to the 0 character -> use '\0'
Kurt