1
我无法找到关于如何锁定文件以进行读写的答案。如何锁定文件以进行读写访问O_RDWR
lock.l_type = F_WRLCK //for write.
lock.l_type = F_RDLCK //for read
lock.l_type = F_RDLCK|F_WRLCK //maybe for read/write????
下面的代码是否正确?
fd=MyOpenWrite(name,O_RDWR); //for read/write
//(open file for read/write, but lock for write)
...
fd=MyOpenRead(name,O_RDONLY); //open and lock for read
...
fd=MyOpenWrite(name,O_CREAT|O_WRONLY|O_TRUNC); //for write
...
fd=MyOpenWrite(name,O_WRONLY|O_APPEND); //for append
int MyOpenRead(char *name,int flags) {
int fd;
struct flock lock;
fd = open(name,flags);
if (fd<0) return -1;
lock.l_type = F_RDLCK;
lock.l_start = 0;
lock.l_whence = SEEK_SET;
lock.l_len = 0;
fcntl(fd,F_SETLKW,&lock);
return fd;
}
int MyOpenWrite(char *name,int flags) {
int fd;
struct stat st;
fd = open(name,flags,S_IREAD|S_IWRITE|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
if (fd<0) return -1;
lock.l_type = F_WRLCK;
lock.l_start = 0;
lock.l_whence = SEEK_SET;
lock.l_len = 0;
fcntl(fd,F_SETLKW,&lock);
return fd;
}
嗯。我需要独占锁定读取,写入和读取/写入(仅限一个进程)。我无法理解哪种锁定类型对我来说会更好。但如何锁定文件的读/写打开(... O_RDWR)?谢谢。 – nms 2013-03-19 10:42:22
@nms有一些进程读取你正在写入的数据是非常没用的,并导致竞态条件。所以没有写锁只能阻止作者。写锁将锁定读者和作者。 – nos 2013-03-19 11:14:22
好的。至于读锁。我想它应该锁定写入甚至其他读者。那么我的代码是否正确?谢谢。 – nms 2013-03-19 11:41:30