tset - initialization
This program initializes terminals.
First, @TSET@ 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.
Next, @TSET@ determines the type of terminal that you are using.
This determination is done as follows, using the first terminal type
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 convention, 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 TYPEMAPPING 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.
reset - reinitialization
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:
-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
-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 information.
-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 output, 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,
-w 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”.
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 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
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 (1979), written by Kurt Shoens.
A separate tset command was provided in 2BSD by Eric Allman. While
the oldest published source (from 1979) provides both programs,
Allman's comments in the 2BSD source code indicate that he began work
in October 1977, continuing development over the next few years.
In 1980, Eric Allman modified tset to provide a “reset” feature when
the program was invoked as reset.
The ncurses implementation was lightly adapted from the 4.4BSD
sources for a terminfo environment by Eric S. Raymond
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 obsolete. However, each of those systems still provides
tset. In fact, the commonly-used reset utility is always an alias
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:
· 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 TERMCAP.
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
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
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
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 -c and -w options are not found in earlier implementations.
However, a different window size-change feature was provided in
· 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 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:
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.
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
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