lock — reserve a terminal
lock [−p] [−t timeout]
lock requests a password from the user, reads it again for verification and then will normally not relinquish the terminal until the password is repeated. There are two other conditions under which it will terminate: it will timeout after some interval of time and it may be killed by someone with the appropriate permission.
A password is not requested, instead the user’s current login password is used. If the user has an S/Key key, they may also use it to unlock the terminal. To do this the user should enter "s/key" at the unlock "Key:" prompt. The user will then be issued an S/Key challenge to which they may respond with a six-word S/Key one-time password.
The time limit (default 15 minutes) is changed to timeout minutes.
The lock command appeared in 3.0BSD.
BSD June 6, 1993 BSD