/* cc -o pthreads pthreads.c -lpthread */

#include <stdio.h>

#include <pthread.h>

void *thread_fn(void *p)
{
    int *arg = p;
    fprintf(stderr, "Hello from thread %d\n", *arg);
    return NULL;
}

int main(void)
{
    const int N = 10;
    pthread_t threads[N];
    int args[N];
    int i;

    for (i = 0; i < N; i++)
    {
        args[i] = i;
        if (pthread_create(threads + i, NULL, thread_fn, args + i) != 0)
        {
            return 1;
        }
    }

    // ...

    for (i = 0; i < N; i++)
    {
        if (pthread_join(threads[i], NULL) != 0)
        {
            return 2;
        }
    }

    return 0;
}