- terminal initialization
] [-e ch
] [ -k ch
] [-m mapping
] [-e ch
] [ -k ch
] [-m mapping
This program initializes terminals.
retrieves the current terminal mode settings for your
terminal. It does this by successively testing
- the standard error,
- standard output,
- standard input and
- ultimately “/dev/tty”
to obtain terminal settings. Having retrieved these settings, tset
remembers which file descriptor to use when updating settings.
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
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 convention, getty
does this job by setting
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
mappings are then applied (see the section TERMINAL TYPE MAPPING
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 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,
- if the “-w” option is enabled,
tset may update the terminal's window size.
- If the window size cannot be obtained from the operating
system, but the terminal description (or environment, e.g., LINES
and COLUMNS variables specify this), use this to set the operating
system's notion of the window size.
- if the “-c” option is enabled, the
backspace, interrupt and line kill characters (among many other things)
- 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
- 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
sets the terminal modes to
- sets cooked and echo modes,
- turns off cbreak and raw modes,
- turns on newline translation and
- resets any unset special characters to their default
before doing the terminal initialization described above. Also, rather than
using the terminal initialization
strings, it uses the terminal
command is useful after a program dies leaving a terminal in an
- 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
- 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 TERMINAL TYPE MAPPING 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 archaic.
- 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
SETTING THE ENVIRONMENT 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(3X). Normally this has no effect, unless setupterm
is not able to detect the window size.
The arguments for the -e
, 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”.
If neither -c
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
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
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
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
, 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.
options maps 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
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
option argument be placed within single quote characters, and that
users insert a backslash character (“\”) before any
exclamation marks (“!”).
command appeared in 2BSD (April 1979), written by Kurt Shoens.
This program set the erase
characters to ^H
(backspace) and @
respectively. Mark Horton improved that in 3BSD
(October 1979), adding intr
characters as well as changing the program to avoid modifying any
Later in 4.1BSD (December 1980), Mark Horton added a call to the tset
program using the -I
options, i.e., using that to improve
the terminal modes. With those options, that version of reset
use the termcap database.
A separate tset
command was provided in 2BSD by Eric Allman. While the
oldest published source (from 1979) provides both tset
, 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
. Rather than simply copying the existing program, in this merged
used the termcap database to do additional
(re)initialization of the terminal. This version appeared in 4.1cBSD, late in
Other developers (e.g., Keith Bostic and Jim Bloom) continued to modify
until 4.4BSD was released in 1993.
implementation was lightly adapted from the 4.4BSD sources
for a terminfo environment by Eric S. Raymond <email@example.com>.
Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
(POSIX.1-2008) nor X/Open Curses Issue 7 documents tset
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
obsolete. However, each of those systems still provides
. In fact, the commonly-used reset
utility is always an
alias for tset
utility provides for backward-compatibility with BSD
environments (under most modern UNIXes, /etc/inittab
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
- The -S option of BSD tset no longer works; it
prints an error message to the standard error and dies.
- The -s option only sets TERM, not
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
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
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
instead. The -a
, 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
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
, 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
no longer implies the
option. Also, the interaction between the - option and the
argument in some historic implementations of tset
options are not found in earlier implementations.
However, a different window size-change feature was provided in 4.4BSD.
- 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.
- In ncurses, tset obtains the window size using
setupterm, which may be from the operating system, the LINES
and COLUMNS environment variables or the terminal description.
Obtaining the window size from the terminal description is common to both
implementations, but considered obsolescent. 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 operating system (and
would still fail). For that reason, the LINES
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
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
- system port name to terminal type mapping database (BSD
- terminal capability database
This describes ncurses
version 6.0 (patch 20170902).