login - sign on
login [ username ]
The login command is used when a user initially signs on, or it may be used at any time to
change from one user to another. The latter case is the one summarized above and
described here. See `How to Get Started' for how to dial up initially.
If login is invoked without an argument, it asks for a user name, and, if appropriate, a
password. Echoing is turned off (if possible) during the typing of the password, so it
will not appear on the written record of the session.
After a successful login, accounting files are updated and the user is informed of the
existence of .mail and message-of-the-day files. Login initializes the user and group IDs
and the working directory, then executes a command interpreter (usually sh(1)) according
to specifications found in a password file. Argument 0 of the command interpreter is
Login is recognized by sh(1) and executed directly (without forking).
/etc/passwd password file
init(8), newgrp(1), getty(8), mail(1), passwd(1), passwd(5)
`Login incorrect,' if the name or the password is bad.
`No Shell', `cannot open password file', `no directory': consult a programming counselor.