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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   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 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 6.2 (patch 20210904).



                                                                       tset(1)