#include <stdio.h>
#include <pthread.h>
#include <time.h>

// set a default number of threads to create
#define NUM_THREADS 20

struct timespec tp;
int nThreads, sleepTime;

/*** The thread function for each thread created in main, takes the identifier as an argument  ***/
void* sayHello ( void *ip ) {

    // sleep for some random number of seconds
    sleepTime = rand() % 2;
    sleep( sleepTime );

    int i = ( int ) ip;

    // print a message for each thread
    printf( "Hi I'm thread %d\n and my sleep time is %d\n", i, sleepTime );
    fflush( stdout );

    pthread_exit(NULL);
}


int main( int argc, char *argv[] ) {

     // loop counter
     int i;


     // ensure we have the correct number of args
     if( argc != 2 ) {
         printf( "Usage: ./nThreads nThreads\n" );
         fflush( stdout );
         return 1;
     }


    nThreads = atoi(argv[1]);

    // create an array of thread ids
    pthread_t threads[NUM_THREADS];

    // seed the srandom function using clock ticks
    srand ( clock_gettime( CLOCK_REALTIME, &tp ) );


    // print a message in main
    printf( "Creating %d threads in main...\n ", nThreads  );
    fflush( stdout );

    // create the required number of threads, calling sayHello for each thread
    for( i = 0; i < nThreads; i++ ) {
        pthread_create( &threads[i], NULL, sayHello, (void*)i  );
    }

    // wait for all threads to finish their execution
    for( i = 0; i < nThreads; i++ ) {
        pthread_join( threads[i], NULL );
    }

    return 0;
}