BloombergLP::bdls::FilesystemUtil::lock

Acquire a lock for the file with the specified descriptor. If lockWriteFlag is true, acquire an exclusive write lock; otherwise acquire a (possibly) shared read lock. The calling thread will block until the lock is acquired. Return 0 on success, and a non‐zero value otherwise. Note that this operation locks the indicated file for use by the current process, but the behavior is unspecified (and platform‐dependent) when either attempting to lock descriptor multiple times, or attempting to lock another descriptor referring to the same file, within a single process.