login(1) INTERACTIVE UNIX System login(1)
NAME
login - sign on
SYNOPSIS
login [name [env-var ...]]
DESCRIPTION
The login command is used at the beginning of each terminal
session and allows you to identify yourself to the system.
It may be invoked as a command or by the system when a con-
nection is first established. Also, it is invoked by the
system when a previous user has terminated the initial shell
by typing a CTRL-D to indicate an ``end-of-file.''
If login is invoked as a command, it must replace the ini-
tial command interpreter. This is accomplished by typing:
exec login
from the initial shell.
login asks for your user name (if not supplied as an argu-
ment), and, if appropriate, your password. Echoing is
turned off (where possible) during the typing of your pass-
word, so it will not appear on the written record of the
session.
If you make a mistake in the login procedure you will
receive the message:
Login incorrect
and a new login prompt will appear. If you make five
incorrect login attempts, all five may be logged in
/usr/adm/loginlog (if it exists) and the line will be
dropped.
If you do not complete the login successfully within a cer-
tain period of time (e.g., 1 minute), you will probably be
silently disconnected.
After a successful login, the user ID, the group IDs, the
working directory, and the command interpreter (usually
sh(1) or csh(1)) are initialized. If the shell /bin/sh is
running, accounting files are updated, the procedure
/etc/profile is performed, the message-of-the-day (if any)
is printed, and the file .profile in the working directory
is executed, if it exists. If the shell /bin/csh is run-
ning, the .login and .cshrc files in the working directory
are executed, if they exist. These specifications are found
in the /etc/passwd file entry for the user. The name of the
command interpreter is - followed by the last component of
the interpreter's path name (i.e., -sh). If this field in
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login(1) INTERACTIVE UNIX System login(1)
the password file is empty, then the default command inter-
preter /bin/sh is used. If this field is *, then the named
directory becomes the root directory, the starting point for
path searches for path names beginning with a slash (/). At
that point, login is re-executed at the new level which must
have its own root structure, including /etc/login and
/etc/passwd.
The basic environment is initialized to:
HOME=your-login-directory
PATH=:/bin:/usr/bin
SHELL=last-field-of-passwd-entry
MAIL=/usr/mail/your-login-name
TZ=timezone-specification
The environment may be expanded or modified by supplying
additional arguments to login, either at execution time or
when login requests your login name. The arguments may take
either the form xxx or xxx=yyy. Arguments without an equal
sign are placed in the environment as:
Ln=xxx
where n is a number starting at 0 and is incremented each
time a new variable name is required. Variables containing
an = are placed into the environment without modification.
If they already appear in the environment, then they replace
the older value. There are exceptions. The variables HOME,
PATH, SHELL, MAIL, IFS, TZ, HZ, CDPATH, and LOGNAME cannot
be changed. This prevents people, logging into restricted
shell environments, from spawning secondary shells which are
not restricted. Both login and getty understand simple
single-character quoting conventions. Typing a backslash in
front of a character quotes it and allows the inclusion of
such things as spaces and tabs.
FILES
/etc/utmp accounting
/etc/wtmp accounting
/usr/mail/your-name mailbox for user your-name
/usr/adm/loginlog record of failed login attempts
/etc/motd message-of-the-day
/etc/passwd password file
/etc/profile system profile (/bin/sh only)
.profile user's login profile (/bin/sh only)
SEE ALSO
mail(1), sh(1), newgrp(1M), su(1M).
loginlog(4), passwd(4), profile(4), environ(5) in the
INTERACTIVE SDS Guide and Programmer's Reference Manual.
DIAGNOSTICS
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login(1) INTERACTIVE UNIX System login(1)
login incorrect if the user name or the password cannot be
matched.
No shell, cannot open password file, or no directory: con-
sult a UNIX system programming counselor.
No utmp entry. If you attempted to execute login as a com-
mand without using the shell's exec internal command or
attempted to execute login as a command from a shell other
than the initial shell, you must execute login from the
lowest level shell.
NOTES
The file /etc/default/login contains special login informa-
tion including the flag PASSREQ. When PASSREQ is set to YES
(PASSREQ=YES), users will be required to have a password.
When a user without a password logs in and PASSREQ=YES, the
user will be forced to add a password before the user is
allowed access to the system. One exception to this
requirement is if password aging is turned on for the user
and the NULL password has not been aged. In this case, the
user will be allowed to access the system without a password
until the NULL password has been aged, or until the root
user forces the password to be aged (passwd -f command).
ADDED VALUE
This entry, supplied by INTERACTIVE Systems Corporation,
contains enhancements to UNIX System V.
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