How to check if a variable is NULL in C/C++?

In C or C, there is no special way to compare NULL values. We can use if statement to check if a variable is null.

Here we will see a program. We will try to open a file in read mode that does not exist on the system. So the function will return null value. We can check it using if statement. Please see the code for better understanding.

Sample code

#include <stdio.h>
main() {
   //try to open a file in read mode, which is not present
   FILE *fp;
   fp = fopen("hello.txt", "r");
   if(fp == NULL)
      printf("File does not exists");
   fclose(fp);
}

Output

File does not exists

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