Code testing possible forking and file bug

main.c

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

int main()
{
    int order;
    FILE* file = fopen("sample_input.txt", "r");
    if (file != NULL)
    {
        printf("parent process: %d\n", getpid());
        int n;
        while ((n = fscanf(file, "%d", &order)) == 1)
        {
            int f = fork();
            if (f == 0)
            {
                break;
            }
        }

        //fclose(file);

        printf("process %d (parent %d)\n", getpid(), getppid());
    }
}

sample_input.txt

5 2 8 1 4 2

On Linux (kernel version 4.16.0) and using GCC (tested with version 7.3.0) and libc version 2.27, this program will not stop reading from the file after reading the last value. Instead the parent process will repeatedly read the last value from the file and create more and more processes.

On my system the parent process will stop reading after a while though.

If the fclose call is uncommented, then it will all work okay, with the parent process stop reading after the last value.