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    Length: 3073 (0xc01)
    Types: TextFile
    Notes: UNIX file
    Names: »getty.8«

└─⟦26887b7e0⟧ Bits:30009717 Comet 32 harddisk image
    └─⟦28c352965⟧ »/a« UNIX Filesystem
        └─⟦this⟧ »usr/man/man8/getty.8« 

TextFile

.ig
	@(#)getty.8	2.1	7/1/84
	@(#)Copyright (C) 1983 by National Semiconductor Corp.
..
.TH GETTY 8 
.SH NAME
getty  \- set terminal mode
.SH SYNOPSIS
.B /etc/getty
[ char ]
.SH DESCRIPTION
.I Getty
is invoked by
.IR init (8)
immediately after a terminal is opened,
following the making of a connection.
.I Getty
reads a login name and,
while doing so,
attempts to adapt the system to the speed and type
of terminal being used.
.PP
.I Init
calls
.I getty
with an argument specified by the
.I ttys
file entry for the terminal line.
.I Getty
uses this argument,
which defaults to `0',
to select a particular line configuration
to use in reading the login name.
After setting line characteristics,
.I getty
types a banner containing
the system's name
(from
.IR /usr/include/ident.h ),
the machine's host name,
and the `login:' message.
Then it reads the user's name,
a character at a time.
If a null character is received,
it is assumed to be the result
of the user pushing the `break' (`interrupt') key.
.I Getty
treats this event as an indication
that the current line configuration is incorrect.
It establishes a new set of line charactersistics,
retypes the banner,
throws away any characters it has already read,
and tries again to read the user's name.
Successive `break' characters cycle through
additional line configurations.
.PP
The user's name is terminated by a new-line or
carriage-return character.
The latter results in the system being set to
treat carriage returns appropriately
(see
.IR stty (2)).
.PP
The user's name is scanned to see if
it contains any lower-case alphabetic characters;
if not,
and if the name is nonempty,
the system is told to map any future upper-case characters
into the corresponding lower-case characters.
.PP
Finally,
.I login
is called with the user's name as argument.
.PP
When invoked,
.I getty
reads the file
.I /etc/gettytab
to determine the collection of line configurations
it is to use in reading the user's login name.
Most line configurations
specify that raw mode is to be used (wake up on every character),
that echo is to be suppressed,
and either parity allowed.
They are usually arranged in cycles
whose members differ only in baud rate.
See
.IR gettytab (5)
for details.
.PP
A line configuration can specify automatic line speed determination.
In this case
.I getty
sets the line speed initially to 1200 baud
and reads a character,
which it assumes to be a carriage-return.
It then sets the line speed based on
the results of the read.
This technique is only partially reliable;
see
.B BUGS
below.
.PP
If
.I getty
cannot read
.IR gettytab ,
it uses a built in
300 baud line configuration,
which is provided as a hedge against disaster.
.SH FILES
.nf
.ta \w'/etc/gettytab'u+(4n)
/etc/gettytab	table of terminal line descriptions
/etc/ttys	source of argument given to getty
.fi
.SH "SEE ALSO"
init(8), login(1), stty(2), ttys(5), gettytab(5)
.SH BUGS
The autobauding code fails for some line speeds,
but works for the most common speeds.
It should be tested in a particular environment
before being used in production.