TSET(1) BSD TSET(1)
NAME
tset - terminal dependent initialization
SYNOPSIS
tset [ options ] [ -m [ident][test baudrate]:type ] ... [ type ]
reset [ options ] [ -m [ident][test baudrate]:type ] ... [ type ]
DESCRIPTION
tset sets up your terminal when you first log in to a UNIX system. It
does terminal dependent processing such as setting erase and kill
characters, setting or resetting delays, sending any sequences needed to
properly initialized the terminal, and the like. It first determines the
type of terminal involved, and then does necessary initializations and
mode settings. The type of terminal attached to each UNIX port is
specified in the /etc/ttys(5) database. Type names for terminals may be
found in the termcap(5) database. If a port is not wired permanently to
a specific terminal (not hardwired) it will be given an appropriate
generic identifier such as dialup.
In the case where no arguments are specified, tset simply reads the
terminal type out of the environment variable TERM and re-initializes the
terminal. The rest of this text concerns itself with mode and
environment initialization, typically done once at login, and options
used at initialization time to determine the terminal type and set up
terminal modes.
When used in a start-up script (.profile for sh(1) users or .login for
csh(1) users) it is desirable to give information about the type of
terminal you will usually use on ports that are not hardwired. These
ports are identified in /etc/ttys as dialup or plugboard or arpanet, etc.
To specify what terminal type you usually use on these ports, the -m
(map) option flag is followed by the appropriate port type identifier, an
optional baud rate specification, and the terminal type. (The effect is
to "map" from some conditions to a terminal type, that is, to tell tset
"If I'm on this kind of port, guess that I'm on that kind of terminal".)
If more than one mapping is specified, the first applicable mapping
prevails. A missing port type identifier matches all identifiers. Any
of the alternate generic names given in /etc/termcap may be used for the
identifier.
A baudrate is specified as with stty(1), and is compared with the speed
of the diagnostic output (which should be the control terminal). The
baud rate test may be any combination of: >, @, <, and !; @ means "at"
and ! inverts the sense of the test. To avoid problems with
metacharacters, it is best to place the entire argument to -m within '
characters; csh(1) users must also put a \ before any ! used here.
Thus
tset -m 'dialup>300:adm3a' -m dialup:dw2 -m 'plugboard:?adm3a'
causes the terminal type to be set to an adm3a if the port in use is a
dialup at a speed greater than 300 baud; to a dw2 if the port is
(otherwise) a dialup (that is, at 300 baud or less). If the type finally
determined by tset begins with a question mark, the user is asked if s/he
really wants that type. A null response means to use that type;
otherwise, another type can be entered which will be used instead. Thus,
in the above case, the user will be queried on a plugboard port as to
whether they are actually using an adm3a.
If no mapping applies and a final type option, not preceded by a -m, is
given on the command line then that type is used; otherwise the type
found in the /etc/ttys database will be taken to be the terminal type.
This should always be the case for hardwired ports.
It is usually desirable to return the terminal type, as finally
determined by tset, and information about the terminal's capabilities to
a shell's environment. This can be done using the - option; using the
Bourne shell, sh(1):
export TERM; TERM=`tset - options...`
or using the C shell, csh(1):
setenv TERM `tset - options...`
With csh it is preferable to use the following command in your .login
file to initialize the TERM and TERMCAP environment variables at the same
time. You must set noglob before invoking the tset -s command, and unset
noglob after the tset -s command, as shown in the following example.
set noglob
eval `tset -s options...`
unset noglob
It is also convenient to make an alias in your .cshrc:
alias tset 'eval `tset -s \!*`'
This allows the command:
tset 2621
to be invoked at any time to set the terminal and environment. Note to
Bourne shell users: It is not possible to get this aliasing effect with
a shell script, because shell scripts cannot set the environment of their
parent. (If a process could set its parent's environment, none of this
nonsense would be necessary in the first place.)
These commands cause tset to place the name of your terminal in the
variable TERM in the environment; see environ(7).
Once the terminal type is known, tset engages in terminal driver mode
setting. This normally involves sending an initialization sequence to
the terminal, setting the single character erase (and optionally the
line-kill (full line erase)) characters, and setting special character
delays. Tab and newline expansion are turned off during transmission of
the terminal initialization sequence.
On terminals that can backspace but not overstrike (such as a CRT), and
when the erase character is the default erase character (`#' on standard
systems), the erase character is changed to BACKSPACE (CTRL/H).
OPTIONS
-ec Set the erase character to be the named character c on all
terminals, the default being the backspace character on the
terminal, usually ^H (CTRL/H). The character c can either be
typed directly, or entered using the hat notation used here.
-kc This option is similar to -e but it applies to the line kill
character rather than the erase character; c defaults to ^X
(for purely historical reasons). The kill characters is left
alone if -k is not specified. The hat notation can also be
used for this option.
-ic This option is similar to -e but it applies to the interrupt
character rather than the erase character; c defaults to ^C
(CTRL/C). The hat notation can also be used for this option.
- The name of the terminal finally decided upon is output on the
standard output. This is intended to be captured by the shell
and placed in the environment variable TERM.
-s Print the sequence of csh commands to initialize the
environment variables TERM and TERMCAP based on the name of the
terminal finally decided upon.
-n On systems with the Berkeley 4BSD tty driver, specifies that
the new tty driver modes should be initialized for this
terminal. For a CRT, the CRTERASE and CRTKILL modes are set
only if the baud rate is 1200 or greater. See tty(4) for more
detail.
-I Suppresses transmitting terminal initialization strings.
-Q Suppresses printing the "Erase set to" and "Kill set to"
messages.
If tset is invoked as reset, it will set cooked and echo modes, turn off
cbreak and raw modes, turn on newline translation, and restore special
characters to a sensible state before any terminal-dependent processing
is done. Any special character that is found to be NULL or "-1" is reset
to its default value. All arguments to tset may be used with reset.
This is most useful after a program dies leaving a terminal in a funny
state. You may have to type "<LF>reset<LF>" to get it to work since <CR>
may not work in this state. Often none of this will echo.
EXAMPLES
These examples all assume the Bourne shell and use the - option. If you
use csh, use one of the variations described above. Note that a typical
use of tset in a .profile or .login will also use the -e and -k options,
and often the -n or -Q options as well. These options have not been
included here to keep the examples small. (NOTE: some of the examples
given here appear to take up more than one line, for text processing
reasons. When you type in real tset commands, you must enter them
entirely on one line.)
At the moment, you are on a 2621. This is suitable for typing by hand
but not for a .profile, unless you are always on a 2621.
export TERM; TERM=`tset - 2621`
You have an h19 at home which you dial up on, but your office terminal is
hardwired and known in /etc/ttys.
export TERM; TERM=`tset - -m dialup:h19`
You have a switch which connects everything to everything, making it
nearly impossible to key on what port you are coming in on. You use a
vt100 in your office at 9600 baud, and dial up to switch ports at 1200
baud from home on a 2621. Sometimes you use someone elses terminal at
work, so you want it to ask you to make sure what terminal type you have
at high speeds, but at 1200 baud you are always on a 2621. Note the
placement of the question mark, and the quotes to protect the greater
than and question mark from interpretation by the shell.
export TERM; TERM=`tset - -m 'switch>1200:?vt100' -m 'switch<=1200:2621'
All of the above entries will fall back on the terminal type specified in
/etc/ttys if none of the conditions hold. The following entry is
appropriate if you always dial up, always at the same baud rate, on many
different kinds of terminals. Your most common terminal is an adm3a. It
always asks you what kind of terminal you are on, defaulting to adm3a.
export TERM; TERM=`tset - ?adm3a`
If the file /etc/ttys is not properly installed and you want to key
entirely on the baud rate, the following can be used:
export TERM; TERM=`tset - -m '>1200:vt100' 2621`
Here is a fancy example to illustrate the power of tset and to hopelessly
confuse anyone who has made it this far. You dial up at 1200 baud or
less on a concept100, sometimes over switch ports and sometimes over
regular dialups. You use various terminals at speeds higher than 1200
over switch ports, most often the terminal in your office, which is a
vt100. However, sometimes you log in from the university you used to go
to, over the ARPANET; in this case you are on an ALTO emulating a dm2500.
You also often log in on various hardwired ports, such as the console,
all of which are properly entered in /etc/ttys. You want your erase
character set to control H, your kill character set to control U, and
don't want tset to print the "Erase set to Backspace, Kill set to Control
U" message.
export TERM; TERM=`tset -e -k^U -Q - -m 'switch<=1200:concept100' -m
'switch:?vt100' -m dialup:concept100 -m arpanet:dm2500`
FILES
/etc/ttys port name to terminal type mapping database
/etc/termcap terminal capability database
BUGS
The tset command is one of the first commands a user must master when
getting started on a UNIX system. Unfortunately, it is one of the most
complex, largely because of the extra effort the user must go through to
get the environment of the log-in shell set. Something needs to be done
to make all this simpler, either the login(1) program should do this
stuff, or a default shell alias should be made, or a way to set the
environment of the parent should exist.
This program can't intuit personal choices for erase, interrupt and line
kill characters, so it leaves these set to the local system standards.
tset cannot modify Display Manager key definitions for erase, kill, etc.
SEE ALSO
csh(1), sh(1), stty(1), ttys(5), termcap(5), environ(7)