# 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 ter-
           minal.  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 ques-
           tion 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  deter-
           mined,  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 win-
               dow size.

               If the window size cannot be obtained from  the  operating  system,
               but  the terminal description (or environment, e.g., LINES and COL-
               UMNS variables specify this), use this to set  the  operating  sys-
               tem'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 initializa-
               tion  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   Set the erase character to ch.

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

           -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 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 charac-
                ters 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 sys-
           tem 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 opera-
           tor 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 con-
           trol terminal).  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 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 exclama-
           tion marks ("!").

## HISTORY

           A reset command appeared in 2BSD (April 1979), 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 pro-
           gram to avoid modifying any user settings.

           Later in 4.1BSD (December 1980), Mark Horton added a call to  the  tset
           program  using  the  -I and -Q options, i.e., using that to improve the
           terminal modes.  With those options, that version of reset did not  use
           the termcap database.

           A separate tset command was provided in 2BSD by Eric Allman.  While the
           oldest published source (from 1979) provides both tset and reset,  All-
           man's  comments  in the 2BSD source code indicate that he began work in
           October 1977, continuing development over the next few years.

           In September 1980, Eric Allman modified tset, adding the code from  the
           existing  "reset"  feature when tset was invoked as reset.  Rather than
           simply copying the existing program, in this merged version, tset  used
           the  termcap database to do additional (re)initialization of the termi-
           nal.  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 mak-
           ing 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 environ-
           ments (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  mes-
               sage 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  let-
           ter)  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  docu-
           mented  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.   How-
           ever, 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 win-
           dow 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 vari-
                able from the environment before looking for the terminal descrip-
                tion.

## 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 6.2 (patch 20201205).

                                                                           tset(1)