NAME
tset
, reset
— terminal
initialization
SYNOPSIS
tset |
[-IQrs ] [- ]
[-e ch]
[-i ch]
[-k ch]
[-m mapping]
[terminal] |
reset |
[-IQrs ] [- ]
[-e ch]
[-i ch]
[-k ch]
[-m mapping]
[terminal] |
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.
- The terminal argument specified on the command line.
- The value of the
TERM
environmental variable. - The terminal type associated with the standard error output device in the /etc/ttys file.
- 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 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.
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 a
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:
-
- The terminal type is displayed to the standard output, and the terminal is not initialized in any way.
-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 below for more information.
-Q
- Don't display any values for the erase, interrupt and line kill characters.
-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 the
csh(1), otherwise, they are for
sh(1).
Note, the csh(1) 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 ... `
To demonstrate a simple use of the -S
option, the following lines in the .login file have
an equivalent effect:
set noglob set term=(`tset -S options ...`) setenv TERM $term[1] unset term unset noglob
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
(.profile for
sh(1)
users or .login for
csh(1) users) 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 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
metacharacters, it is suggested that the entire -m
option argument be placed within single quote characters, and that
csh(1) users insert a backslash character (``\'') before any
exclamation marks (``!'').
ENVIRONMENT
The tset
command uses the
SHELL
and TERM
environment
variables.
FILES
- /etc/ttys
- system port name to terminal type mapping database
- /usr/share/misc/terminfo
- terminal capability database
COMPATIBILITY
The -A
, -E
,
-h
, -u
and
-v
options have been deleted from the
tset
utility. 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. 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.
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 -E
and -S
options have been removed as they only make sense for termcap and
tset
now uses terminfo. As such, the
TERMCAP
entry has been removed from
-s
.
Finally, the tset
implementation has been
completely redone (as part of the addition to the system of a
IEEE Std 1003.1-1988 (“POSIX.1”)
compliant terminal interface) and will no longer compile on systems with
older terminal interfaces.
SEE ALSO
csh(1), sh(1), stty(1), tty(4), terminfo(5), ttys(5), environ(7)
HISTORY
The reset
and tset
commands appeared in 1BSD.