Multithreading in Unix

multithreading.cc

// Compile with g++ -o multithreading.o multithreading.cc -lpthread
#include <pthread.h>
#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <string.h>

typedef struct my_struct {
    int data;
    int random_number;
} my_struct_t;

void* thread(void* str) {
    my_struct_t *local_str = (my_struct_t *)str;
    int i;
    for (i=0;i<5;i++) {
        sleep(local_str->random_number);
        printf("Hello! I am thread %d, i was sleeping for %d seconds\n",
                local_str->data,
                local_str->random_number);
    }
}

int main(int argc, char **argv){
    sigset_t oSignalSet;
    sigemptyset(&oSignalSet);
    sigaddset(&oSignalSet, SIGINT);
    sigaddset(&oSignalSet, SIGABRT);
    sigaddset(&oSignalSet, SIGQUIT);

    pthread_sigmask(SIG_BLOCK, &oSignalSet, NULL);

    pthread_t iThreadId;

    // Declare variable to hold seconds on clock.
    time_t seconds;

    // Get value from system clock and
    // place in seconds variable.
    time(&seconds);

    // Convert seconds to a unsigned
    // integer.
    srand((unsigned int) seconds);

    my_struct_t st1;
    my_struct_t st2;
    my_struct_t st3;
    st1.data = 1;
    st2.data = 2;
    st3.data = 3;
    st1.random_number = rand()%10;
    st2.random_number = rand()%10;
    st3.random_number = rand()%10;

    printf("Parent: Creating and calling threads...\n");
    int iReturnValue1 = pthread_create(&iThreadId, NULL, &thread, (void *)&st1);
    int iReturnValue2 = pthread_create(&iThreadId, NULL, &thread, (void *)&st2);
    int iReturnValue3 = pthread_create(&iThreadId, NULL, &thread, (void *)&st3);

    if (iReturnValue1 < 0 || iReturnValue2 < 0 || iReturnValue2 < 0) {
        printf("error creating thread '%s'.\n", strerror(errno));
    }

    int iSignalNumber;
    sigwait(&oSignalSet, &iSignalNumber);
    printf("exit after receiving signal #%d.\n", iSignalNumber);
    exit(0);
}