Provided by: ncurses-bin_6.1+20181013-2ubuntu2_amd64 bug

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

       ·   the standard error,

       ·   standard output,

       ·   standard input and

       ·   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,

       ·   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.

       ·   if the “-c” option is enabled, the  backspace,  interrupt  and  line  kill  characters
           (among many other things) are set

       ·   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).

       ·   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:

       ·   sets cooked and echo modes,

       ·   turns off cbreak and raw modes,

       ·   turns on newline translation and

       ·   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:

       ·   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.

       ·   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 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 program 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, 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 terminal.  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(8) 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:

       ·   The  -S option of BSD tset no longer works; it prints an error message to the standard
           error and dies.

       ·   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.

       ·   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.

       ·   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).

       /etc/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 6.1 (patch 20181013).

                                                                                          tset(1)