# tset 1

    tset(1)                     General Commands Manual                    tset(1)

## NAME

           tset, reset - terminal initialization

## SYNOPSIS

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

## DESCRIPTION

### tset - initialization

           This program initializes terminals.

           First,  tset  retrieves  the  current  terminal  mode settings for your
           terminal.  It does this by successively testing

           o   the standard error,

           o   standard output,

           o   standard input and

           o   ultimately "/dev/tty"

           to obtain terminal settings.  Having  retrieved  these  settings,  tset
           remembers which file descriptor to use when updating settings.

           Next,  tset  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 terminal description for the terminal is retrieved.  If
           no terminal description is found for the type, the user is prompted for
           another terminal type.

           Once the terminal description is retrieved,

           o   if  the  "-w"  option  is  enabled,  tset may update the terminal's
               window size.

               If the window size cannot be obtained from  the  operating  system,
               but  the  terminal  description  (or  environment,  e.g., LINES and
               COLUMNS variables specify this), use  this  to  set  the  operating
               system's notion of the window size.

           o   if  the  "-c"  option is enabled, the backspace, interrupt and line
               kill characters (among many other things) are set

           o   unless  the  "-I"  option  is  enabled,  the   terminal   and   tab
               initialization  strings  are sent to the standard error output, and
               tset waits one second (in case a hardware reset was issued).

           o   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.

### reset - reinitialization

           When invoked as reset, tset sets the terminal modes to "sane" values:

           o   sets cooked and echo modes,

           o   turns off cbreak and raw modes,

           o   turns on newline translation and

           o   resets any unset special characters to their default values

           before doing the terminal initialization described above.  Also, rather
           than  using  the  terminal initialization strings, it uses the terminal
           reset strings.

           The reset command is useful after a program dies leaving a terminal  in
           an abnormal state:

           o   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.

           o   Also, the terminal will often not echo the command.

## OPTIONS

           The options are as follows:

           -c   Set control characters and modes.

           -e ch
                Set the erase character to ch.

           -I   Do  not  send  the  terminal  or tab initialization strings to the
                terminal.

           -i ch
                Set the interrupt character to ch.

           -k ch
                Set the line kill character to ch.

           -m mapping
                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(3x).
                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".

           If neither -c or -w is given, both options are assumed.

## 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 -m options maps 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

           A reset command appeared in 1BSD (March 1978), written by Kurt  Shoens.
           This  program set the erase and kill characters to ^H (backspace) and @
           respectively.  Mark Horton improved that in 3BSD (October 1979), adding
           intr,  quit,  start/stop  and  eof  characters  as well as changing the
           program to avoid modifying any user settings.  That  version  of  reset
           did not use the termcap database.

           A  separate tset command was provided in 1BSD by Eric Allman, using the
           termcap database.  Allman's comments in the source code  indicate  that
           he began work in October 1977, continuing development over the next few
           years.

           According to comments in the source code, the tset program was modified
           in  September  1980,  to use logic copied from the 3BSD "reset" when it
           was invoked as reset.  This version appeared in 4.1cBSD, late in 1982.

           Other developers (e.g., Keith Bostic and Jim Bloom) continued to modify
           tset until 4.4BSD was released in 1993.

           The  ncurses implementation was lightly adapted from the 4.4BSD sources
           for a terminfo environment by Eric S. Raymond <esr@snark.thyrsus.com>.

## COMPATIBILITY

           Neither IEEE Std 1003.1/The Open  Group  Base  Specifications  Issue  7
           (POSIX.1-2008) nor X/Open Curses Issue 7 documents tset or reset.

           The  AT&T  tput utility (AIX, HPUX, Solaris) incorporated the terminal-
           mode manipulation as well as termcap-based features such  as  resetting
           tabstops  from  tset  in  BSD  (4.1c), presumably with the intention of
           making tset obsolete.  However, each of those  systems  still  provides
           tset.   In fact, the commonly-used reset utility is always an alias for
           tset.

           The  tset  utility  provides  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.

           A few options are different because the TERMCAP variable is  no  longer
           supported under terminfo-based ncurses:

           o   The  -S  option  of  BSD  tset  no longer works; it prints an error
               message to the standard error and dies.

           o   The -s option only sets TERM, not TERMCAP.

           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 -a, -d, and
           -p options are therefore omitted from the usage summary above.

           Very  old  systems,  e.g., 3BSD, used a different terminal driver which
           was replaced in 4BSD in the early 1980s.  To  accommodate  these  older
           systems,  the  4BSD  tset  provided a -n option to specify that the new
           terminal driver should be used.  This implementation does  not  provide
           that choice.

           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.

           The  -c  and  -w  options  are  not  found  in earlier implementations.
           However, a different window size-change feature was provided in 4.4BSD.

           o   In 4.4BSD, tset uses the window size from the  termcap  description
               to  set  the  window  size if tset is not able to obtain the window
               size from the operating system.

           o   In ncurses, tset obtains the window size using setupterm, which may
               be  from  the  operating  system, the LINES and COLUMNS environment
               variables or the terminal description.

           Obtaining the window size from the terminal description  is  common  to
           both  implementations,  but considered obsolescent.  Its only practical
           use is for hardware terminals.  Generally speaking, a window size would
           be  unset  only if there were some problem obtaining the value from the
           operating system (and setupterm would still fail).   For  that  reason,
           the  LINES  and COLUMNS environment variables may be useful for working
           around window-size problems.  Those  have  the  drawback  that  if  the
           window  is  resized, those variables must be recomputed and reassigned.
           To do this more easily, use the resize(1) program.

## 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).

           /usr/share/terminfo
                terminal capability database

## SEE ALSO

           csh(1),   sh(1),   stty(1),   curs_terminfo(3x),  tty(4),  terminfo(5),
           ttys(5), environ(7)

           This describes ncurses version 6.3 (patch 20211021).

                                                                           tset(1)