Read an integer from stdin (in C)

Question

I want to write a C program that takes as input an integer, and outputs its square. Here is what I have tried.

However,

• ./a.out < 3 outputs 32768, and
• ./a.out < 4 also outputs 32768.

Where am I wrong? Thanks.

#include <stdio.h>

int main(){
  int myInt;
  scanf("%d", &myInt);
  printf("%d\n",myInt*myInt);
}

Answer 1

It looks like what you're trying to do is

echo 4 | ./a.out

the syntax for < is

program < input_file

whereas | is

command_with_output | program