TSET(1) BSD General Commands Manual TSET(1)NAME
tset, reset — terminal initialization
SYNOPSIStset [-IQrSs] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]
reset [-IQrSs] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]
The tset utility initializes terminals. It 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 environment 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 termcap entry for the terminal is
retrieved. If no termcap entry is found for the type, the user is
prompted for another terminal type.
Once the termcap entry is retrieved, the window size, backspace, inter‐
rupt 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 dis‐
played 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 initializa‐
tion described above. This is useful after a program dies leaving a ter‐
minal 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:
- The terminal type is displayed to the standard output, and the ter‐
minal 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 ter‐
-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
-Q Do not display any values for the erase, interrupt and line kill
-r Print the terminal type to the standard error output.
-S Print the terminal type and the termcap entry to the standard out‐
put. See the section below on setting the environment for details.
-s Print the sequence of shell commands to initialize the environment
variables TERM and TERMCAP 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 and -s options.
When the -S option is specified, the terminal type and the termcap entry
are written to the standard output, separated by a space and without a
terminating newline. This can be assigned to an array by csh and ksh
users and then used like any other shell array.
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 environment variable ends in ``csh'', the commands are for the csh,
otherwise, they are for sh(1). 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 ... `
To demonstrate a simple use of the -S option, the following lines in the
.login file have an equivalent effect:
set term=(`tset -S options ...`)
setenv TERM $term
setenv TERMCAP "$term"
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 environment 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 desir‐
able 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 condi‐
tions 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 (delim‐
ited 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 termi‐
nal). The terminal type is a string.
If the terminal type is not specified on the command line, the -m map‐
pings 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
users insert a backslash character (``\'') before any exclamation marks
The tset command utilizes the SHELL and TERM environment variables.
/etc/ttys system port name to terminal type mapping data‐
/usr/share/misc/termcap terminal capability database
The -A, -E, -h, -u and -v options have been deleted from the tset util‐
ity. None of them were documented in 4.3BSD and all are of limited util‐
ity 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 argu‐
ments, 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 his‐
toric implementations of tset has been removed.
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”) compli‐
ant terminal interface) and will no longer compile on systems with older
SEE ALSOcsh(1), sh(1), stty(1), tty(4), termcap(5), ttys(5), environ(7)HISTORY
The tset command appeared in 3.0BSD.
BSD June 9, 1993 BSD