NAME

tset, reset − set or reset the teletype bits to a sensible state

SYNOPSIS

tset [ options ]
reset

DESCRIPTION

Tset causes terminal dependent processing such as setting erase and kill characters, setting or resetting delays, and the like.  It first determines the type of terminal involved, names for which are specified by the /etc/termcap data base, and then does necessary initializations and mode settings.  In the case where no argument types are specified, tset simply reads the terminal type out of the environment variable TERM and re-initializes the terminal.  The rest of this manual concerns itself with type initialization, done typically once at login, and options used at initialization time to determine the terminal type and set up terminal modes. 

When used in a startup script ".profile" (for sh(1) users) or ".login" (for csh(1) users), it is desirable to give information about the types of terminal usually used, for terminals which are connected to the computer through a modem. These ports are initially identified as being dialup or plugboard or arpanet etc.  To specify what terminal type is usually used on these ports, −m is followed by the appropriate port type identifier, an optional baud-rate specification, and the terminal type to be used if the mapping conditions are satisfied.  If more than one mapping is specified, the first applicable mapping prevails.  A missing type identifier matches all identifiers. 

Baud rates are specified as with stty(1), and are compared with the speed of the diagnostic output (which is almost always the control terminal). The baud rate test may be any combination of: >, =, <, @, and !; @ is a synonym for = and !  inverts the sense of the test.  To avoid problems with metacharacters, it is best to place the entire argument to −m within ´´ characters; users of csh(1) must also put a "\" before any "!" used here.

Thus

tset −m ´dialup>300:adm3a´ −m dialup:dw2

causes the terminal type to be set to an adm3a if the port in use is a dialup at a speed greater than 300 baud; to a dw2 if the port is (otherwise) a dialup (i.e., at 300 baud or less).  If the type above begins with a question mark, the user is asked if the user really wants that type.  A null response means to use that type; otherwise, another type can be entered which will be used instead.  For other ports the port type will be taken from the /etc/ttytype file or a final, default type option may be given on the command line not preceded by a −m.  A ttytype may be preceded with a question mark in /etc/ttytype for prompting (this is an enhancement over standard tset). 

It is often desirable to return the terminal type, as specified by the −m options, and information about the terminal to a shell’s environment.  This can be done using the −s option; using the Bourne shell, sh(1):

eval `tset −s options ... `

or using the C shell, csh(1):

tset -s options ... > tset$$
source tset$$
rm tset$$

or:

unsetenvTERMCAP
setnoglob tmp=(‘tset -S -Q‘)
setenvTERM "$tmp[1]"
setenvTERMCAP "$tmp[2]"
unsettmp noglob

These commands cause tset to generate as output a sequence of shell commands which place the variables TERM and TERMCAP in the environment; see environ(5).

Once the terminal type is known, tset engages in terminal mode setting.  This normally involves sending an initialization sequence to the terminal and setting the single character erase (and optionally the line-kill (full line erase)) characters. 

On terminals that can backspace but not overstrike (such as a CRT), and when the erase character is the default erase character ("#" on standard systems), the erase character is changed to a Control-H (backspace). 

Other options are:

−e set the erase character to be the named character c on all terminals, the default being the backspace character on the terminal, usually ^H. 

−k is similar to −e but for the line kill character rather than the erase character; c defaults to ^X (for purely historical reasons); ^U is the preferred setting.  No kill processing is done if −k is not specified. 

−I suppresses outputting terminal initialization strings. 

−Q suppresses printing the "Erase set to" and "Kill set to" messages. 

−S Outputs the strings to be assigned to TERM and TERMCAP in the environment rather than commands for a shell. 

Reset sets the terminal to cooked mode, turns off "cbreak" and "raw" modes, turns on "nl", and restores special characters that are undefined to their default values. 

This is most useful after a program dies leaving a terminal in a funny state; you have to type <LF>reset<LF> to get it to work as <CR> often doesn’t work; often none of this will echo. 

It isn’t a bad idea to follow reset with tset.

EXAMPLE

A typical csh ".login" file using tset would be:

set noglob
set term = (‘tset -e -S -r -d?h19‘)
setenv TERM "$term[1]"
setenv TERMCAP "$term[2]"
unset term noglob

This ".login" sets the environment variables TERM and TERMCAP for the user’s current terminal according to the file /etc/ttytype.  If the terminal line is a dialup line, the user is prompted for the proper terminal type. 

Reset may be used to return the user’s terminal to a usable state after being accidentally set by an interrupted process to unusual modes. 

FILES

/etc/ttytypeterminal id to type map database
/etc/termcapterminal capability database

SEE ALSO

csh(1), sh(1), stty(1), environ(4), ttytype(4), termcap(5). 

BUGS

Should be merged with stty(1).

Reset doesn’t set tabs properly; it can’t intuit personal choices for interrupt and line kill characters, so it leaves these the old UNIX standards ^? (delete) for interrupt and @ for line kill. 

It could well be argued that the shell should be responsible for insuring that the terminal remains in a sane state; this would eliminate the need for this program. 

NOTES

For compatibility with earlier versions of tset, a number of flags are accepted whose use is discouraged:

−d type equivalent to −m dialup:type

−p type equivalent to −m plugboard:type

−a type equivalent to −m arpanet:type

−E c Sets the erase character to c only if the terminal can backspace. 

− prints the terminal type on the standard output

−r prints the terminal type on the diagnostic output. 

AUTHOR

Eric Allman

Version 2.3  —  July 04, 1985