# tset 1 2023-12-23 ncurses 6.4 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
               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.

### 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, 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.

## 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 6.4                       2023-12-23                           tset(1)