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Manual Pages  — TSET

NAME

tset, reset – terminal initialization

CONTENTS

SYNOPSIS


tset [-IQrSs] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]
reset [-IQrSs] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]

DESCRIPTION

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.

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, 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 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 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
  Do not display any values for the erase, interrupt and line kill characters.
-r
  Print the terminal type to the standard error output.
-S
  Print the terminal type and the termcap entry to the standard output. 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 noglob
set term=(`tset -S options ...`)
setenv TERM $term[1]
setenv TERMCAP "$term[2]"
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 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 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: "amp;>", "amp;<", "amp;@", and "amp;!"; "amp;>" means greater than, "amp;<" means less than, "amp;@" means equal to and "!amp;" 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 users insert a backslash character (``\'') before any exclamation marks (``!'').

ENVIRONMENT

The tset command utilizes the SHELL and TERM environment variables.

FILES

/etc/ttys system port name to terminal type mapping database
/usr/share/misc/termcap
  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 BSD 4.3 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.

Finally, the tset implementation has been completely redone (as part of the addition to the system of a IEEE Std 1003.1-88 ("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), termcap(5), ttys(5), environ(7)

HISTORY

The tset and reset utilities first appeared in BSD 1 .

AUTHORS

The original version of tset was written by Eric P. Allman in October 1977, and reset was originally written by Kurt Shoens. The current version also contains code by Zeyd M. Ben-Halim, Eric S. Raymond, and Thomas E. Dickey.
TSET (1) June 6, 2015
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