tset, reset - terminal initialization
tset [-IQVqrs] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]
A reset [-IQVqrs] [-] [-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 below 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 stan-
dard 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.
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:
-q 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 archaic.
-e Set the erase character to ch.
-I Do not send the terminal or tab initialization strings to the ter-
-Q Don’t display any values for the erase, interrupt and line kill
-V reports the version of ncurses which was used in this program, and
-i Set the interrupt character to ch.
-k Set the line kill character to ch.
-m Specify a mapping from a port type to a terminal. See below for
-r Print the terminal type to the standard error output.
-s Print the sequence of shell commands to initialize the environment
variable TERM to the standard output. See the section below on
setting the environment for details.
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’’.
SETTING THE ENVIRONMENT
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 ... `
TERMINAL TYPE MAPPING
When the terminal is not hardwired into the system (or the current sys-
tem 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 partic-
ular 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 opera-
tor 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 map-
pings 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 terminal.
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 exclama-
tion 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 <firstname.lastname@example.org>.
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 let-
ter) set the terminal to use upper-case only. This feature has been
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 docu-
mented 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
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 the SHELL and TERM environment variables.
system port name to terminal type mapping database (BSD versions
terminal capability database
csh(1), sh(1), stty(1), tty(4), termcap(5), ttys(5), environ(7)
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