排他锁。除加锁进程外其他进程没有对已加锁文件读写访问权限。
LOCK_EX an exclusive lock. This denies all other processes both read and write access to the file.
这些系统对文件进行加锁，这样在某个时间只有一个开发人员对中心仓库具有写入权限。
These systems lock files so that only one developer has write access to the central repository at a time.
看起来我所找到的任何一种所谓的文件加锁的正确指南，之后又都进行了更新。
It seemed that for every guideline I found spelling out the correct way to lock files, a subsequent correction was posted.
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