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

       •   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  ter‐
       minal 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 Sys‐
       tem-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 TERMI‐
       NAL 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 termi‐
       nal 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  sec‐
            tion 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 environ‐
       ment.  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 stan‐
       dard  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 .pro‐
       file 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 de‐
       rived from the /etc/ttys file or the TERM environmental variable is often something generic like  network,  dialup,  or  un‐
       known.   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 particu‐
       lar 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  sug‐
       gested  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  develop‐
       ment 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 re‐
       set.  Rather than simply copying the existing program, in this merged version, tset used the termcap database  to  do  addi‐
       tional (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  imple‐
       mentation 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 accommo‐
       date 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 pro‐
       vided 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 COL‐
       UMNS  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  re‐
            moves 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)

Usage: tset [options] [terminal]

Options:
  -c          set control characters
  -e ch       erase character
  -I          no initialization strings
  -i ch       interrupt character
  -k ch       kill character
  -m mapping  map identifier to type
  -Q          do not output control key settings
  -q          display term only, do no changes
  -r          display term on stderr
  -s          output TERM set command
  -V          print curses-version
  -w          set window-size

If neither -c/-w are given, both are assumed.