baitap1_2.cc

basic about Unix ptheard and pid

#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <wait.h>
#include <iostream.h>
#include <stdlib.h>
#include <sys/shm.h>
#include <sys/stat.h>

#define MAX_SEQUENCE 10

typedef struct
{
   long fib_sequence[MAX_SEQUENCE]; 
    int sequence_size ;
} shared_data ;

int main(int argc, char *argv[])
{	
	if (argc != 2)
	{
		cout<<"So^' do^i' so^' kho^ng ho*p. le^.\n";
		return 1;
	}
	
	int n = atoi(argv[1]);
	
	if (n<0 || n>MAX_SEQUENCE)
	{
		cout<<"Error\n";
		return 1;
	}

	long fib_sequence[MAX_SEQUENCE];

	int seg_id=shmget(IPC_PRIVATE,sizeof(shared_data),S_IRUSR|S_IWUSR);
	shared_data *m;
	m=(shared_data*)shmat(seg_id,NULL,0);

	m->sequence_size = n;

	m->fib_sequence[0]=0;
	m->fib_sequence[1]=1;

        pid_t pid ;
        pid = fork();

        if (pid == 0 )
        {
               for (int i=2;i<m->sequence_size;i++)
			m->fib_sequence[i]=m->fib_sequence[i-1]+m->fib_sequence[i-2];
		
        }
        else if (pid > 0)
        {
              wait(NULL);
		for (int i=0;i<m->sequence_size;i++)
			cout<<m->fib_sequence[i]<<endl;	

	 	shmdt(m);
		shmctl(seg_id,IPC_RMID,NULL);
	         
              _exit(0);
        }

}