This is part 1 with some extra consumers. Runs on OS X too.

part1.c

// 1. (70pts) Develop a monitor in C (using pthread library functions) or Java to solve the producer-consumer problem. [Hint: your program can be cased on the pseudo-code on Page 7 of 2013-3-4's lecture]

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

#define CAN_CONSUME_PATH "/tmp/canConsume"
#define CAN_PRODUCE_PATH "/tmp/canProduce"

sem_t* canConsume;
sem_t* canProduce;

int consumerThreadId = 1;

//here we define our threads 0 and 1
pthread_t tids[5];

int itemsInBuffer = 0;

// This is our buffer, it can be any size
#define BUFFER_SIZE 5
int buffer[BUFFER_SIZE];

void* consumerThreadFunction(void* x){
    int id = consumerThreadId++;
  printf("Consumer %d: [thread starts]\n",id);
    while(1){
        // wait until we've been cleared to consume
        printf("Consumer %d: [check]\n",id);
        
        sem_wait(canConsume);
        if(itemsInBuffer > 0){
            printf("Consumer %d: [Consuming] itemsInBuffer: %d\n",id,itemsInBuffer);
            //consume something, by changing the buffer
            // value from a 1 to a 0. I guess we consume 1's
            // buffer[itemsInBuffer-1] = 0;

            // reduce the count of the items in the buffer
            itemsInBuffer--;
            printf("Consumer %d: [done] itemsInBuffer: %d\n",id,itemsInBuffer);
            sem_post(canProduce);
        }
        printf("Consumer %d: [sleeping]\n",id);
    }
    return 0;
}
void* producerThreadFunction(void* x)
{
	printf("Producer thread starts.\n");
    while(1){
      int sleepTime =rand() % 1000;
      printf("Producer: [sleep %d]\n",sleepTime);
        usleep(sleepTime*1000);
        printf("Producer: [check]\n");
        sem_wait(canProduce);
        while(itemsInBuffer < (BUFFER_SIZE)){
            printf("Producer: [Producing] itemsInBuffer: %d\n",itemsInBuffer);            
            // reduce the count of the items in the buffer
            itemsInBuffer++;
            printf("Producer: [Done] itemsInBuffer: %d\n",itemsInBuffer);
            sem_post(canConsume);
        }        
    }
    return 0;
}


//Initializes the semaphores, returns 0 on success
int initializeSemaphores();

// closes and unlinks the semaphores
void cleanupSemaphores();

int main() {
    // sem_init() returns 0 on success; on error, -1 is returned...
    cleanupSemaphores();

    if(initializeSemaphores() ==  0){
        printf("Creating threads...\n");
        pthread_create(tids,  NULL, producerThreadFunction, NULL);
        pthread_create(tids+1,NULL, consumerThreadFunction,NULL);
        pthread_create(tids+2,NULL, consumerThreadFunction,NULL);
        pthread_create(tids+3,NULL, consumerThreadFunction,NULL);
        pthread_create(tids+4,NULL, consumerThreadFunction,NULL);

        
        // pthread_create(tids+2,NULL,th2,NULL);
        
        pthread_join(tids[0], NULL);
        pthread_join(tids[1], NULL);
        pthread_join(tids[2], NULL);
        pthread_join(tids[3], NULL);
        pthread_join(tids[4], NULL);

        // clean up after ourselves
        cleanupSemaphores();
        // use useful return value
        return 0;
    } else {
        // explain we have a problem initializing, if I was serious I would use errno.
        printf("Unable to initialize the semaphore\n");
        //useful return value
        return -1;
    }
}


int initializeSemaphores(){
    int returnValue = 1;
    
    // I develop on Mac OS X and there are no nameless semaphores
    // so I am stuck using named semaphores
    if ((canConsume = sem_open(CAN_CONSUME_PATH, O_CREAT, 0644, 1)) == SEM_FAILED ) {
        perror("sem_open");
    } else {
        
        if ((canProduce = sem_open(CAN_PRODUCE_PATH, O_CREAT, 0644, 1)) == SEM_FAILED ) {
            perror("sem_open");
        } else {
            returnValue = 0;
        }
    }
    return returnValue;
}

void cleanupSemaphores(){
    sem_close(canConsume);
    sem_unlink(CAN_CONSUME_PATH);

    sem_close(canProduce);
    sem_unlink(CAN_PRODUCE_PATH);
}