#include <bits/stdc++.h>
using namespace std;
#define M 5

int fact(int n)             //線性遞歸
{
    if (n < 0)
        return 0;
    else if(n == 0 || n == 1)
        return 1;
    else
        return n * fact(n - 1);
}
 
int facttail(int n, int a)   //尾遞歸
{
    if (n < 0)
        return 0;
    else if (n == 0)
        return 1;
    else if (n == 1)
        return a;
    else
        return facttail(n - 1, n * a);
}

int facttail1(int n, int a)  
{
    while(n > 0)
    {
        a = n * a;
        n--;
	}
	return a;
}
 
int main()
{
    //printf("%p", facttail);
    int a = fact(M);
    int b = facttail(M, 1);
    cout << "A:" << a <<endl;
    cout << "B:" << b <<endl;
}

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

int main()
{
	int num = 0;
	pid_t pid = fork();
	if(pid == 0) //子進程
	{
		while(1)
		{
			num++;
			printf("child:pid:[%d] num:[%d]\n", getpid(), num);
			sleep(2);
		}
	}
	else
	{
		while(1){
			num = num + 2;
			printf("parent:pid:[%d] num:[%d]\n", getpid(), num);
			sleep(2);
		}
	}
	return 0;
}

show follow-fork-mode
show detach-on-fork
set follow-fork-mode [parent|child]   
set detach-on-fork [on|off]

#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <errno.h>
#include <unistd.h>
 
/*全局變量*/
int sum = 0;
/*互斥量 */
pthread_mutex_t mutex;
/*聲明線程運行服務(wù)程序*/
void* pthread_function1 (void*);
void* pthread_function2 (void*);
 
int main (void)
{
    /*線程的標(biāo)識符*/
    pthread_t pt_1 = 0;
    pthread_t pt_2 = 0;
    int ret = 0;
    /*互斥初始化*/
    pthread_mutex_init (&mutex, NULL);
    /*分別創(chuàng)建線程1、2*/
    ret = pthread_create( &pt_1,                  //線程標(biāo)識符指針
                           NULL,                  //默認屬性
                           pthread_function1,     //運行函數(shù)
                           NULL);                 //無參數(shù)
    if (ret != 0)
    {
        perror ("pthread_1_create");
    }
	
    ret = pthread_create( &pt_2,                  //線程標(biāo)識符指針
                          NULL,                   //默認屬性
                          pthread_function2,      //運行函數(shù)
                          NULL);                  //無參數(shù)
    if (ret != 0)
    {
        perror ("pthread_2_create");
    }
    
    /*等待線程1、2的結(jié)束*/
    pthread_join (pt_1, NULL);
    pthread_join (pt_2, NULL);
 
    printf ("main programme exit!\n");
    return 0;
}
 
/*線程1的服務(wù)程序*/
void* pthread_function1 (void*a)
{
    int i = 0;
    printf ("This is pthread_1!\n");
    for( i=0; i<3; i++ )
    {
        pthread_mutex_lock(&mutex); /*獲取互斥鎖*/
        /*臨界資源*/
        sum++;
        printf ("Thread_1 add one to num:%d\n",sum);
        pthread_mutex_unlock(&mutex); /*釋放互斥鎖*/
        /*注意，這里以防線程的搶占，以造成一個線程在另一個線程sleep時多次訪問互斥資源，所以sleep要在得到互斥鎖后調(diào)用*/
        sleep (1);
    }
    pthread_exit ( NULL );
}
 
/*線程2的服務(wù)程序*/
void* pthread_function2 (void*a)
{
    int i = 0;
    printf ("This is pthread_2!\n");
    for( i=0; i<5; i++ )
    {
        pthread_mutex_lock(&mutex); /*獲取互斥鎖*/
        /*臨界資源*/
        sum++;
        printf ("Thread_2 add one to num:%d\n",sum);
        pthread_mutex_unlock(&mutex); /*釋放互斥鎖*/
        /*注意，這里以防線程的搶占，以造成一個線程在另一個線程sleep時多次訪問互斥資源，所以sleep要在得到互斥鎖后調(diào)用*/
        sleep (1);
    }
    pthread_exit ( NULL );
}