tset
terminal initialization
see also :
sh - stty - tty
Synopsis
tset
[-IQVcqrsw] [-] [-e
ch] [-i ch] [-k
ch] [-m mapping]
[terminal]
reset [-IQVcqrsw] [-]
[-e ch] [-i ch]
[-k ch] [-m mapping]
[terminal]
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description
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
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 TYPE MAPPING 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
<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. 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
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, and exits.
-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’’.
compatibility
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.
environment
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.
files
/etc/ttys
system port name to terminal type mapping database (BSD versions
only).
/etc/terminfo
terminal capability database
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 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 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
(’’!’’).
history
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
<esr[:at:]snark.thyrsus[:dot:]com>.
see also
csh, sh ,
stty , curs_terminfo(3X), tty , terminfo, ttys,
environ
This describes
ncurses version 5.9 (patch 20110404).