Zad2 - mutex

#include "stdio.h"
#include "unistd.h"
#include "pthread.h"
#include "stdlib.h"
#include "errno.h"
#include "limits.h"
#include "math.h"
#include "semaphore.h"
#include "string.h"
#define BUFFER_SIZE 100

pthread_mutex_t mut[4];

void emptyBuffer( char* buff);
void *threadCzytelnik(void *arg);

struct targs{
    int numWatku;
};
char common[BUFFER_SIZE];
int koniecPliku = 0;
int main()
{
    FILE *fp;
    emptyBuffer(common);
    for(int i = 0; i < 4; i++)
    pthread_mutex_init(&mut[i], NULL);
    pthread_attr_t attrs;
    pthread_attr_init(&attrs);
    //pthread_attr_setdetachstate(&attrs, PTHREAD_CREATE_DETACHED );

    pthread_t threadId[3];
    fp = fopen("/etc/passwd","r");
    struct targs watki[3];
    {
        int i = 0;
        for(;i < 3; i++)
        {
            watki[i].numWatku = i+1;
            pthread_create(&threadId[i], &attrs, threadCzytelnik, &watki[i]);
            pthread_detach(threadId[i]);
        }
    }
    pthread_mutex_lock(&mut[1]);
    pthread_mutex_lock(&mut[2]);
    pthread_mutex_lock(&mut[3]);
    char *l;
    int i = 0;
    while( 1 ) {
        pthread_mutex_lock(&mut[0]);
        l = fgets(common, BUFFER_SIZE, fp);
        if(l==0) break;
        pthread_mutex_unlock(&mut[1]);
    }
    fclose(fp);
    koniecPliku = 1;

}

void emptyBuffer( char* buff)
{
    {
        int i = 0;
        for(;i<BUFFER_SIZE;i++)
        {
            buff[i] = 0;
        }
    }
}


void *threadCzytelnik(void *arg)
{

    struct targs *argptr = (struct targs*) arg;

    char nazwaPliku[80];
    int num = argptr->numWatku;
    snprintf(nazwaPliku, 80, "./MATEUSZ%d", num);
    FILE *fp = fopen(nazwaPliku, "w");
    while(1)
    {
        pthread_mutex_lock(&mut[num]);
            if(koniecPliku)
            {
                fflush(fp);
                fclose(fp);
                pthread_exit(0);
            }
            fwrite(common, sizeof(char), strlen(common), fp);
            printf("%d-%s\n", argptr->numWatku, common);
            fflush(stdout);
            pthread_mutex_unlock(&mut[(num + 1)%4]);

    }
}