Thread: Write a program that recursively calculates the X-th Fibonacci number.....

Why don't you show us an example of a program that recursively calculates the X-th Fibonacci number?

Why don't you show us an example of a program that uses a separate process?

These are two things that you can do along the way to arriving at a desired solution.

I tried to do it, technically it works, I'm not 100% sure that it uses a distinct process for each call, can you confirm it?

Code:

#include <stdio.h>
#include <stdlib.h>
#include<unistd.h>
#include<sys/wait.h>

size_t fibonacci(size_t n)
{
  pid_t pid1, pid2;
  size_t fib;
  int status;

  switch (n) {
  case 0:
    return 0;
  case 1:
  case 2:
    return 1;
  default:
    break;
  }

  pid1 = fork();

  if (pid1 == 0)
    exit(fibonacci(n - 1));
  else if (pid1 < 0) {
    printf("ERRORE");
    exit(EXIT_FAILURE);
  }

  pid2 = fork();

  if (pid2 == 0)
    exit(fibonacci(n - 2));
  else if (pid2 < 0) {
    printf("ERRORE");
    exit(EXIT_FAILURE);
  }
  if (waitpid(pid1, &status, 0) == -1) {
    printf("ERRORE");
    exit(EXIT_FAILURE);
  }

  fib = WEXITSTATUS(status);

  if (waitpid(pid2, &status, 0) == -1) {
    printf("ERRORE");
    exit(EXIT_FAILURE);
  }

  return fib + WEXITSTATUS(status);
}

int main(int argc, char *argv[])
{

  int a = atoi(argv[1]);
  printf("Calcolo fibonacci di %d \n", a);
  printf("L' %so numero di Fibonacci e' %d.\n", argv[1], fibonacci(a));


}

You really need to improve your spacing.

You seem to be trying to return the fib through the program's exit status.
That's not going to work.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
 
int main() {
    if (fork() == 0)
        exit(12345);
    int status = -1;
    wait(&status);
    printf("%d\n", WEXITSTATUS(status));  // prints 57 (12345 % 256) for me
    printf("%d\n", status); // prints 14592 for me
    return 0;
}

BTW, don't post code with markup in it. Copy/paste it as plain text.

I didn't realize that the input was restricted to 0 to 10.
In that case it will sort of work, but it's an incredibly stupid idea.

> I didn't realize that the input was restricted to 0 to 10.
Probably because the homework relies on using the extremely limited range of what is allowed in an exit status.

Other than that, the OPs answer looks like it does what is asked.