tset - Cheap VPS LLC


Section: User Commands (1)
Return to Main Contents



tset, reset – terminal initialization


tset [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]

reset [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]


Tset initializes terminals.
Tset first determines the type of terminal that you are using.
This determination is done as follows, using the first terminal type found.

1. The terminal argument specified on the command line.

2. The value of the TERM environmental variable.

3. (BSD systems only.) The terminal type associated with the standard
error output device in the /etc/ttys file. (On Linux and
System-V-like UNIXes, getty does this job by setting
TERM according to the type passed to it by /etc/inittab.)

4. The default terminal type, “unknown”.

If the terminal type was not specified on the command-line, the -m
option mappings are then applied (see the section

for more information).
Then, if the terminal type begins with a question mark (“?”), the
user is prompted for confirmation of the terminal type. An empty
response confirms the type, or, another type can be entered to specify
a new type. Once the terminal type has been determined, the terminfo
entry for the terminal is retrieved. If no terminfo entry is found
for the type, the user is prompted for another terminal type.

Once the terminfo entry is retrieved, the window size, backspace, interrupt
and line kill characters (among many other things) are set and the terminal
and tab initialization strings are sent to the standard error output.
Finally, if the erase, interrupt and line kill characters have changed,
or are not set to their default values, their values are displayed to the
standard error output.
Use the -c or -w option to select only the window sizing
versus the other initialization.
If neither option is given, both are assumed.

When invoked as reset, tset sets cooked and echo modes,
turns off cbreak and raw modes, turns on newline translation and
resets any unset special characters to their default values before
doing the terminal initialization described above. This is useful
after a program dies leaving a terminal in an abnormal state. Note,
you may have to type


(the line-feed character is normally control-J) to get the terminal
to work, as carriage-return may no longer work in the abnormal state.
Also, the terminal will often not echo the command.

The options are as follows:


Set control characters and modes.

Set the erase character to ch.


Do not send the terminal or tab initialization strings to the terminal.

Set the interrupt character to ch.

Set the line kill character to ch.

Specify a mapping from a port type to a terminal.
See the section

for more information.


Do not display any values for the erase, interrupt and line kill characters.
Normally tset displays the values for control characters which
differ from the system’s default values.

The terminal type is displayed to the standard output, and the terminal is
not initialized in any way. The option `-‘ by itself is equivalent but

Print the terminal type to the standard error output.

Print the sequence of shell commands to initialize the environment variable
TERM to the standard output.
See the section

for details.


reports the version of ncurses which was used in this program, and exits.

Resize the window to match the size deduced via setupterm.
Normally this has no effect,
unless setupterm is not able to detect the window size.

The arguments for the -e, -i, and -k
options may either be entered as actual characters or by using the `hat’
notation, i.e. control-h may be specified as “^H” or “^h”.


It is often desirable to enter the terminal type and information about
the terminal’s capabilities into the shell’s environment.
This is done using the -s option.

When the -s option is specified, the commands to enter the information
into the shell’s environment are written to the standard output. If
the SHELL environmental variable ends in “csh”, the commands
are for csh, otherwise, they are for sh.
Note, the csh commands set and unset the shell variable
noglob, leaving it unset. The following line in the .login
or .profile files will initialize the environment correctly:

    eval `tset -s options … `


When the terminal is not hardwired into the system (or the current
system information is incorrect) the terminal type derived from the
/etc/ttys file or the TERM environmental variable is often
something generic like network, dialup, or unknown.
When tset is used in a startup script it is often desirable to
provide information about the type of terminal used on such ports.

The purpose of the -m option is to map
from some set of conditions to a terminal type, that is, to
tell tset
“If I’m on this port at a particular speed, guess that I’m on that
kind of terminal”.

The argument to the -m option consists of an optional port type, an
optional operator, an optional baud rate specification, an optional
colon (“:”) character and a terminal type. The port type is a
string (delimited by either the operator or the colon character). The
operator may be any combination of “>”, “<”, “@”, and “!”; “>”
means greater than, “<” means less than, “@” means equal to
and “!” inverts the sense of the test.
The baud rate is specified as a number and is compared with the speed
of the standard error output (which should be the control terminal).
The terminal type is a string.

If the terminal type is not specified on the command line, the -m
mappings are applied to the terminal type. If the port type and baud
rate match the mapping, the terminal type specified in the mapping
replaces the current type. If more than one mapping is specified, the
first applicable mapping is used.

For example, consider the following mapping: dialup>9600:vt100.
The port type is dialup , the operator is >, the baud rate
specification is 9600, and the terminal type is vt100. The result of
this mapping is to specify that if the terminal type is dialup,
and the baud rate is greater than 9600 baud, a terminal type of
vt100 will be used.

If no baud rate is specified, the terminal type will match any baud rate.
If no port type is specified, the terminal type will match any port type.
For example, -m dialup:vt100 -m :?xterm
will cause any dialup port, regardless of baud rate, to match the terminal
type vt100, and any non-dialup port type to match the terminal type ?xterm.
Note, because of the leading question mark, the user will be
queried on a default port as to whether they are actually using an xterm

No whitespace characters are permitted in the -m option argument.
Also, to avoid problems with meta-characters, it is suggested that the
entire -m option argument be placed within single quote characters,
and that csh users insert a backslash character (“”) before
any exclamation marks (“!”).


The tset command appeared in BSD 3.0. The ncurses implementation
was lightly adapted from the 4.4BSD sources for a terminfo environment by Eric
S. Raymond <[email protected]>.


The tset utility has been provided for backward-compatibility with BSD
environments (under most modern UNIXes, /etc/inittab and getty(1)
can set TERM appropriately for each dial-up line; this obviates what was
tset‘s most important use). This implementation behaves like 4.4BSD
tset, with a few exceptions specified here.

The -S option of BSD tset no longer works; it prints an error message to stderr
and dies. The -s option only sets TERM, not TERMCAP. Both these
changes are because the TERMCAP variable is no longer supported under
terminfo-based ncurses, which makes tset -S useless (we made it die
noisily rather than silently induce lossage).

There was an undocumented 4.4BSD feature that invoking tset via a link named
`TSET` (or via any other name beginning with an upper-case letter) set the
terminal to use upper-case only. This feature has been omitted.

The -A, -E, -h, -u and -v
options were deleted from the tset
utility in 4.4BSD.
None of them were documented in 4.3BSD and all are
of limited utility at best.
The -a, -d, and -p options are similarly
not documented or useful, but were retained as they appear to be in
widespread use. It is strongly recommended that any usage of these
three options be changed to use the -m option instead. The
-n option remains, but has no effect. The -adnp options are therefore
omitted from the usage summary above.

It is still permissible to specify the -e, -i, and -k options without
arguments, although it is strongly recommended that such usage be fixed to
explicitly specify the character.

As of 4.4BSD, executing tset as reset no longer implies the -Q
option. Also, the interaction between the – option and the terminal
argument in some historic implementations of tset has been removed.


The tset command uses these environment variables:


tells tset whether to initialize TERM using sh or
csh syntax.

Denotes your terminal type.
Each terminal type is distinct, though many are similar.

may denote the location of a termcap database.
If it is not an absolute pathname, e.g., begins with a `/’,
tset removes the variable from the environment before looking
for the terminal description.




system port name to terminal type mapping database (BSD versions only).

terminal capability database




This describes ncurses
version 5.7 (patch 20090207).













Back to Top

PayPal Logo┬ęCheap VPS LLC - Leader of affordable VPS Hosting Services