logical operation trick

logical_operation_trick.c

#include <stdio.h>

void file_open(FILE** fp)
{
      char str[1024];
      *fp || (((*fp = fopen("test.txt", "w"), fprintf(*fp, "hello!\n")), fclose(*fp)), *fp = fopen("test.txt", "r"));
      fscanf(*fp, "%s", str);
      printf("%s", str);

}

int main()
{
      FILE *in;
      in = fopen("test.txt", "r");
      file_open(&in);
      fclose(in);
      return 0;
}