對檔案加鎖，但裡面的資料是錯誤的，先記錄下，以後回來看，是緩衝造成的？？？。用共享記憶體操作是正確的

#include<fcntl.h>
#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/ipc.h>
#include<sys/shm.h>
bool ngx_lock_fd(int fd)
{
    printf("bg  lock pid:%d\n", getpid());
    struct flock  fl;

    fl.l_start = 0;
    fl.l_len = 0;
    fl.l_pid = 0;
    fl.l_type = F_WRLCK;
    fl.l_whence = SEEK_SET;

    if (fcntl(fd,F_SETLK , &fl) == -1) {
	printf("lock false pid %d\n", getpid());
        return false;
    }
    printf("end lock pid:%d\n", getpid());
    return true;
}


bool ngx_unlock_fd(int fd)
{
	
    printf("bg  ulock pid:%d\n", getpid());
    struct flock  fl;

    fl.l_start = 0;
    fl.l_len = 0;
    fl.l_pid = 0;
    fl.l_type = F_UNLCK;
    fl.l_whence = SEEK_SET;

    if (fcntl(fd, F_SETLK, &fl) == -1) {
        return  false;
    }
    printf("end ulock pid:%d\n", getpid());
    return true;
}


int main()
{
	int fd1;
	fd1 = open("test.lock", O_WRONLY | O_CREAT, 0600);
	pid_t fpid;
	int key = getpid();
	fpid = fork();
	int count = 0;
	int *pI = (int*) malloc(sizeof(int));
	*pI = 0;
	if(fpid == 0)
	{
		int shmid = shmget(key, 8, IPC_CREAT|0666|IPC_EXCL);
		if(-1 == shmid)
		{
			printf("1 shmget failed");
			exit(1);
		}
		// 對映共享記憶體，得到虛擬地址
		void *p = shmat(shmid, 0, 0);
		if((void*)-1 == p)
		{
			printf("shmat failed");
			exit(2);
		}
		int *pp = (int*)p;
    	*pp = 0x1;
		while(1)
		{
			if(ngx_lock_fd(fd1))
			{
				int fd;
        			fd = open("test", O_WRONLY | O_CREAT, 0600);
				char buff[1024];
				printf("c count:%d fpid:%d\n", count, fpid);
				read(fd, &buff, 1024);
				printf("r %s\n", buff);
				ftruncate(fd, 0);
				int i = ::atoi(buff);
				snprintf(buff, 1024, "%d\n", ++i);
				write(fd, buff, strlen(buff));
				write(fd1, buff, strlen(buff));
				printf("w %s\n", buff);
				sync();
				close(fd);
				*pI = *pI + 1;
				printf("iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii: %d    %d\n", *pI,getpid());
				
				int *pp = (int*)p;
				*pp = *pp + 0x1;
			
				printf("ssssssssssssssssssssssssssssssssss: %d    %d\n", *pp,getpid());

				
				ngx_unlock_fd(fd1);
			}

			usleep(1000);
		}
	}	
	else
	{	
		sleep(1);
		int shmid = shmget(key, 0, 0);
		if(-1 == shmid)
		{
			printf("shmget failed");
			exit(1);
		}
		// 對映共享記憶體，得到虛擬地址
		void *p = shmat(shmid, 0, 0);
		if((void*)-1 == p)
		{
			printf("shmat failed");
			exit(2);
		}
		
		while(1)
		{
			if(ngx_lock_fd(fd1))
			{
				int fd;
				fd = open("test", O_WRONLY | O_CREAT, 0600);
				char buff[1024];
				printf("p count:%d fpid:%d\n", count, fpid);
				read(fd, &buff, 1024);
				printf("r %s\n", buff);
				ftruncate(fd, 0);
				int i = ::atoi(buff);
				snprintf(buff, 1024, "%d\n", ++i);
				write(fd, buff, strlen(buff));
				write(fd1, buff, strlen(buff));
				printf("w %s\n", buff);
				sync();
				close(fd);
				*pI = *pI + 1;
				printf("iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii: %d    %d\n", *pI,getpid());
				
				int *pp = (int*)p;
				*pp = *pp + 0x1;
				printf("ssssssssssssssssssssssssssssssssss: %d    %d\n", *pp,getpid());

				ngx_unlock_fd(fd1);
			}
			usleep(1000);
		}
	}



	return 0;
}