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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(1) 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(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 ... `


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(1) or csh(1)
            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 20220416).



                                                                       tset(1)