tset(1) tset(1)
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]
This program initializes terminals.
First, tset retrieves the current terminal mode settings
for your terminal. It does this by successively testing
o the standard error,
o standard output,
o standard input and
o ultimately "/dev/tty"
to obtain terminal settings. Having retrieved these set-
tings, tset remembers which file descriptor to use when
updating settings.
Next, tset 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 System-V-like UNIXes and systems using that conven-
tion, 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 TERMINAL TYPE MAPPING for more information).
Then, if the terminal type begins with a question mark
("?"), the user is prompted for confirmation of the termi-
nal 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 terminal
description for the terminal is retrieved. If no terminal
description is found for the type, the user is prompted
for another terminal type.
Once the terminal description is retrieved,
o if the "-w" option is enabled, tset may update the
terminal's window size.
If the window size cannot be obtained from the operat-
ing system, but the terminal description (or environ-
ment, e.g., LINES and COLUMNS variables specify this),
use this to set the operating system's notion of the
window size.
o if the "-c" option is enabled, the backspace, inter-
rupt and line kill characters (among many other
things) are set
o unless the "-I" option is enabled, the terminal and
tab initialization strings are sent to the standard
error output, and tset waits one second (in case a
hardware reset was issued).
o Finally, if the erase, interrupt and line kill charac-
ters 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 the terminal modes to
"sane" values:
o sets cooked and echo modes,
o turns off cbreak and raw modes,
o turns on newline translation and
o resets any unset special characters to their default
values
before doing the terminal initialization described above.
Also, rather than using the terminal initialization
strings, it uses the terminal reset strings.
The reset command is useful after a program dies leaving a
terminal in an abnormal state:
o you may have to type
<LF>reset<LF>
(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.
o Also, the terminal will often not echo the command.
The options are as follows:
-c Set control characters and modes.
-e Set the erase character to ch.
-I Do not send the terminal or tab initialization
strings to the terminal.
-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 the section TERMINAL TYPE MAPPING for more infor-
mation.
-Q 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.
-q The terminal type is displayed to the standard out-
put, and the terminal is not initialized in any way.
The option "-" by itself is equivalent but archaic.
-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 SETTING THE ENVIRONMENT for details.
-V reports the version of ncurses which was used in this
program, and exits.
-w Resize the window to match the size deduced via
setupterm(3x). 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" nota-
tion, i.e., control-h may be specified as "^H" or "^h".
If neither -c or -w is given, both options are assumed.
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 -m options maps from some set of conditions to a ter-
minal type, that is, to tell tset "If I'm on this port at
a particular speed, guess that I'm on that kind of termi-
nal".
The argument to the -m option consists of an optional port
type, an optional operator, an optional baud rate specifi-
cation, 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 applica-
ble 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 termi-
nal type is vt100. The result of this mapping is to spec-
ify 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 exclamation
marks ("!").
A reset command appeared in 2BSD (April 1979), written by
Kurt Shoens. This program set the erase and kill charac-
ters to ^H (backspace) and @ respectively. Mark Horton
improved that in 3BSD (October 1979), adding intr, quit,
start/stop and eof characters as well as changing the pro-
gram to avoid modifying any user settings.
Later in 4.1BSD (December 1980), Mark Horton added a call
to the tset program using the -I and -Q options, i.e.,
using that to improve the terminal modes. With those
options, that version of reset did not use the termcap
database.
A separate tset command was provided in 2BSD by Eric All-
man. While the oldest published source (from 1979) pro-
vides both tset and reset, Allman's comments in the 2BSD
source code indicate that he began work in October 1977,
continuing development over the next few years.
In September 1980, Eric Allman modified tset, adding the
code from the existing "reset" feature when tset was
invoked as reset. Rather than simply copying the existing
program, in this merged version, tset used the termcap
database to do additional (re)initialization of the termi-
nal. This version appeared in 4.1cBSD, late in 1982.
Other developers (e.g., Keith Bostic and Jim Bloom) con-
tinued to modify tset until 4.4BSD was released in 1993.
The ncurses implementation was lightly adapted from the
4.4BSD sources for a terminfo environment by Eric S. Ray-
mond <esr@snark.thyrsus.com>.
Neither IEEE Std 1003.1/The Open Group Base Specifications
Issue 7 (POSIX.1-2008) nor X/Open Curses Issue 7 documents
tset or reset.
The AT&T tput utility (AIX, HPUX, Solaris) incorporated
the terminal-mode manipulation as well as termcap-based
features such as resetting tabstops from tset in BSD
(4.1c), presumably with the intention of making tset obso-
lete. However, each of those systems still provides tset.
In fact, the commonly-used reset utility is always an
alias for tset.
The tset utility provides 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.
A few options are different because the TERMCAP variable
is no longer supported under terminfo-based ncurses:
o The -S option of BSD tset no longer works; it prints
an error message to the standard error and dies.
o The -s option only sets TERM, not TERMCAP.
There was an undocumented 4.4BSD feature that invoking
tset via a link named "TSET" (or via any other name begin-
ning 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 -a,
-d, and -p options are therefore omitted from the usage
summary above.
Very old systems, e.g., 3BSD, used a different terminal
driver which was replaced in 4BSD in the early 1980s. To
accommodate these older systems, the 4BSD tset provided a
-n option to specify that the new terminal driver should
be used. This implementation does not provide that
choice.
It is still permissible to specify the -e, -i, and -k
options without arguments, although it is strongly recom-
mended 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 -c and -w options are not found in earlier implementa-
tions. However, a different window size-change feature
was provided in 4.4BSD.
o In 4.4BSD, tset uses the window size from the termcap
description to set the window size if tset is not able
to obtain the window size from the operating system.
o In ncurses, tset obtains the window size using
setupterm, which may be from the operating system, the
LINES and COLUMNS environment variables or the termi-
nal description.
Obtaining the window size from the terminal description is
common to both implementations, but considered obsoles-
cent. Its only practical use is for hardware terminals.
Generally speaking, a window size would be unset only if
there were some problem obtaining the value from the oper-
ating system (and setupterm would still fail). For that
reason, the LINES and COLUMNS environment variables may be
useful for working around window-size problems. Those
have the drawback that if the window is resized, those
variables must be recomputed and reassigned. To do this
more easily, use the resize(1) program.
The tset command uses these environment variables:
SHELL
tells tset whether to initialize TERM using sh or csh
syntax.
TERM Denotes your terminal type. Each terminal type is
distinct, though many are similar.
TERMCAP
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.
/etc/ttys
system port name to terminal type mapping database
(BSD versions only).
/usr/share/terminfo
terminal capability database
csh(1), sh(1), stty(1), curs_terminfo(3x), tty(4),
terminfo(5), ttys(5), environ(7)
This describes ncurses version 6.0 (patch 20170204).
tset(1)