From the NannyMUD documentation

LAST CHANGE

2001-01-29

FUNCTION

NAME
        lockfile - Lock files while you edit them.


SYNTAX
	lockfile [-crst] [file] [reason]

DESCRIPTION
	With this command you can lock files so that others will be notified
	when they try to edit or move that file. People can still edit or
	remove the file if they 'steal' the lock though. Using the command
	'ed' will automatically put a lock on the file while you edit.

	If you don't use ed, and you are editing files which there is a chanse
	that someone else will edit too you should use lockfile before you
	begin. To lock a file, simply write:

		lockfile 
	or
		lockfile  

	If someone else is already locking the file, you will fail a message
	will be written stating who is locking. If so you can 'steal' the
	lock by adding -s before the filename. If you specify -t instead,
	the lock will only be active until reboot. If you don't give an
	argument, the argument will default to "editing"

	When you are done editing, use:

		lockfile -r 

	to release the lock.

	If you are editing files by ftp, you can lock the file, and before
	you put it back use:

	lockfile -c 

	to see if it has changed while you were editing.

	Also, simply writing 'lockfile' will show all files currently locked.