实验1

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#include <stdio.h>

int main()

{

printf("hello world");

return 0;

}

#include <stdio.h>

#include <sys/types.h>

#include <unistd.h>

#include <fcntl.h>

#include <sys/stat.h>

#include <stdlib.h>

/*struct flock

{

short 1_type;

off_t 1_start;

short 1_whence;

off_t 1_len;

pid_t 1_pid;

}old_lock,lock;*/

int lock_set(int fd,int type)

{

struct flock old_lock,lock;

lock.l_whence = SEEK_SET; //相对位移量的起点：当前位置为文件开头

lock.l_start = 0; //加锁区域的相对位移量

lock.l_len = 0; //加锁区域长度

lock.l_type = type; //锁的类型

lock.l_pid = -1; //记录持有锁的进程

fcntl(fd,F_GETLK,&lock); //fd；根据参数3决定文件是否上锁；struct flock：记录锁的具体状态总：判断文件是否可以上锁

if(lock.l_type != F_UNLCK)

{

if(lock.l_type == F_RDLCK) //读取锁（共享锁）

{

printf("Read lock already set by %d\n",lock.l_pid);

}

else if(lock.l_type == F_WRLCK) //写入锁（排斥锁）

{

printf("Write lock already set by %d\n",lock.l_pid);

}

lock.l_type = type; //l_type的值可能已被F_GETLK修改过

if((fcntl(fd,F_SETLKW,&lock)) < 0) //阻塞式上锁

{

printf("Lock failed:type = %d\n",lock.l_type);

return 1;

}

switch(lock.l_type)

{

case F_RDLCK:

{

printf("Read lock set by %d\n",getpid());

}

break;

case F_WRLCK:

{

printf("Write lock set by%d\n",getpid());

}

break;

case F_UNLCK:

{

printf("Release lock by %d\n",getpid());

return 1;

}

break;

default:

break;

}

return 0;

}

写入锁函数1：

int main(void)

{

int fd;

fd = open("hello.c",O_RDWR|O_CREAT,0644);

if(fd<0)

{

printf("open file error\n");

exit(1);

}

lock_set(fd,F_WRLCK); //给文件写入锁

getchar();

lock_set(fd,F_UNLCK); //给文件解锁

getchar();

close(fd);

exit(0);

读取锁函数2：

int main(void)

{

int fd;

fd =open("hello.c",O_RDWR|O_CREAT,0644);

if(fd<0)

{

printf("open file error\n");

exit(1);

}

lock_set(fd,F_RDLCK);//给文件读取锁

getchar();

lock_set(fd,F_UNLCK);//给文件解锁

getchar();

close(fd);

exit(0);

}

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