# tset 1 2025-01-18 ncurses 6.6 User commands

    tset(1)                          User commands                         tset(1)

## NAME

           tset, reset - initialize or reset terminal state

## SYNOPSIS

           tset  [-IQVcqrsw]  [-]  [-e ch] [-i ch] [-k ch] [-m mapping] [terminal-
           type]
           reset [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m  mapping]  [terminal-
           type]

## 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 environment variable.

           3. (BSD systems only.) The terminal type associated with  the  standard
           error  output  device  in  the  /etc/ttys file.  (On System V hosts and
           systems using that convention, getty(8) does this job by  setting  TERM
           according to the type passed to it by /etc/inittab.)

           4.  The  default  terminal  type, "unknown", is not suitable for curses
           applications.

           If the terminal type was not specified  on  the  command-line,  the  -m
           option  mappings  are  then  applied;  see  subsection  "Terminal  Type
           Mapping".  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,
               if  the  terminal device does not appear to be a pseudoterminal (as
               might be used by a  terminal  emulator  program),  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 canonical ("cooked") and echo modes,

           o   turns off cbreak and raw modes,

           o   turns on newline translation and

           o   resets special input 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.

### 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  environment  variable  ends  in "csh", the commands are for
           csh(1), otherwise, they are for sh(1).  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  environment 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 ("!").

## 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  subsection
                "Terminal Type Mapping".

           -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 subsection "Setting the
                Environment".

           -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.

## 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
                  compiled terminal description database directory

## PORTABILITY

           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, HP-UX, 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 backward compatibility with BSD environments;
           under  most  modern  Unices,  /etc/inittab  and  getty(8)  can set TERM
           appropriately for each dial-up line, obviating  what  was  tset's  most
           important  use.   This  implementation behaves like 4.4BSD tset, with a
           few exceptions we shall consider now.

           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(3x), which
               may be from the operating system, the LINES and COLUMNS environment
               variables or the terminal description.

           Obtaining  the window size from a terminal's type description is common
           to  both  implementations,  but  considered  obsolescent.    Its   only
           practical  use  is  for hardware terminals.  Generally, the window size
           will remain uninitialized only if there were a  problem  obtaining  the
           value  from the operating system (and setupterm would still fail).  The
           LINES and COLUMNS environment variables may thus be useful for  working
           around  window-size  problems, but have the drawback that if the window
           is resized, their  values  must  be  recomputed  and  reassigned.   The
           resize(1) program distributed with xterm(1) assists this activity.

## HISTORY

           A  reset  command written by Kurt Shoens appeared in 1BSD (March 1978).
           It  set  the  erase  and  kill  characters  to  ^H  (backspace)  and  @
           respectively.   Mark Horton improved this reset 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 termcap.

           Eric Allman wrote a distinct tset command for 1BSD, using a  forerunner
           of  termcap  called  ttycap.   Allman's  comments  in  the  source code
           indicate that he began work in  October  1977,  continuing  development
           over  the next few years.  By late 1979, it had migrated to termcap and
           handled the TERMCAP variable.  Later comments indicate  that  tset  was
           modified  in  September  1980 to use logic copied from the 3BSD "reset"
           program when it  was  invoked  as  reset.   This  version  appeared  in
           4.1cBSD,  late  in 1982.  Other developers such as 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
           to use the terminfo API by Eric S. Raymond <esr@snark.thyrsus.com>.

## SEE ALSO

           csh(1),   sh(1),   stty(1),   curs_terminfo(3x),  tty(4),  terminfo(5),
           ttys(5), environ(7)

    ncurses 6.6                       2025-01-18                           tset(1)