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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 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 6.0 (patch 20170506).



                                                                       tset(1)