fcntl_write.c

最新推荐文章于 2023-07-04 10:20:26 发布

xuorui

最新推荐文章于 2023-07-04 10:20:26 发布

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分类专栏： UNIX编程文章标签： include struct

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本文提供了一个使用 C 语言实现的文件锁操作示例代码，包括读锁、写锁及解锁的功能。通过 fcntl 函数对文件进行加锁，并通过 getpid() 获取当前进程 ID 显示锁的状态。

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#include <unistd.h>
#include <sys/file.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
void lock_set(int fd, int type)
{
struct flock lock;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len =0;
while(1){
lock.l_type = type;
if((fcntl(fd, F_SETLK, &lock)) == 0){
if( lock.l_type == F_RDLCK )
printf("read lock set by %d/n",getpid());
else if( lock.l_type == F_WRLCK )
printf("write lock set by %d/n",getpid());
else if( lock.l_type == F_UNLCK )
printf("release lock by %d/n",getpid());
return;
}
fcntl(fd, F_GETLK,&lock);
if(lock.l_type != F_UNLCK){
if( lock.l_type == F_RDLCK )
printf("read lock already set by %d/n",lock.l_pid);
else if( lock.l_type == F_WRLCK )
printf("write lock already set by %d/n",lock.l_pid);
getchar();
}
}
}

int main(void)
{
int fd;
fd=open("hello",O_RDWR | O_CREAT, 0666);
if(fd < 0){
perror("open");
exit(1);
}

lock_set(fd, F_WRLCK);
getchar();
lock_set(fd, F_UNLCK);
getchar();
close(fd);
exit(0);
}