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tset 1

tset(1)                                                         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  set-
       tings,  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  conven-
       tion, 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 termi-
       nal  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 operat-
           ing system, but the terminal description (or  environ-
           ment, 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, inter-
           rupt  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 charac-
           ters  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 infor-
            mation.

       -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  out-
            put,  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"  nota-
       tion, 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  ter-
       minal  type, that is, to tell tset "If I'm on this port at
       a particular speed, guess that I'm on that kind of  termi-
       nal".

       The argument to the -m option consists of an optional port
       type, an optional operator, an optional baud rate specifi-
       cation,  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 applica-
       ble 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  termi-
       nal type is vt100.  The result of this mapping is to spec-
       ify 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 2BSD (April 1979), written by
       Kurt Shoens.  This program set the erase and kill  charac-
       ters  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  All-
       man.   While  the oldest published source (from 1979) pro-
       vides both tset and reset, Allman'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) con-
       tinued 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. Ray-
       mond <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 obso-
       lete.  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 begin-
       ning  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  recom-
       mended  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 implementa-
       tions.  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 termi-
           nal description.

       Obtaining the window size from the terminal description is
       common  to  both  implementations, but considered obsoles-
       cent.  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 oper-
       ating  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 6.0 (patch 20170114).



                                                                tset(1)