// test pthreads and pipe
//
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>

int x = 0; // shared with all threads

void error( const char *msg) { perror(msg); exit(1); }

void *f(void *p) {
#ifdef PART1
  for( int i = 0; i < 5; ++i) { printf( "f %i %i\n", getpid(), ++x); sleep(1); }
  return 0;
#else
  printf( "hi from f\n"); fflush(stdout); // goes into the pipe
  static int v = 99;
  return &v;
#endif
}

// int a[10]; // a is pointer to a[0], a == &a[0]
// f(0) calls f, f is pointer to f(), f == &f

int main( void) {

#ifndef PART1
  int fd[2]; if( pipe(fd) < 0) perror("pipe");
  dup2(fd[0],0); // connect stdin to pipe
  dup2(fd[1],1); // connect stdout to pipe
  close(fd[0]); close(fd[1]); // close unneeded descriptors
#endif

  pthread_t t;
  if( pthread_create( &t, 0, f, 0) != 0) error( "pthread_create");

#ifdef PART1
  for( int i = 0; i < 5; ++i) { printf( "main %i %i\n", getpid(), ++x); sleep(2); }
#else
  char msg[BUFSIZ]; fgets(msg,BUFSIZ,stdin); // read from the pipe
  fprintf( stderr, "main got: %s", msg); // write to terminal
  int *v; // for thread return value
  pthread_join( t, (void**)&v);
  fprintf( stderr, "*v = %i\n", *v);
#endif

}