This command is the same as FcntlCommand.F_SETLK except that if a shared or exclusive lock is blocked by other locks, the process waits until the request can be satisfied. If a signal that is to be caught is received while Syscall.fcntl is waiting for a region, the Syscall.fcntl will be interrupted if the signal handler has not specified the SA_RESTART (see Syscall.sigaction).