man > reset(1)

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

       •   the standard error,

       •   standard output,

       •   standard input and

       •   ultimately “/dev/tty”

       to obtain terminal settings.  Having retrieved these settings, tset remembers which file  de‐
       scriptor 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,

       •   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  de‐
           scription  (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 is‐
           sued).

       •   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 termi‐
       nal 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.

   Setting the Environment
       It is often desirable to enter the terminal type and information about the  terminal's  capa‐
       bilities 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 envi‐
       ronment 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 in‐
       correct) 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 op‐
       tional  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
       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 ac‐
       tually 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 ex‐
       clamation 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  Map‐
            ping”.

       -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 initial‐
            ized 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(3NCURSES).  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).

       /etc/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  ter‐
       minfo-based ncurses:

       •   The -S option of BSD tset no longer works; it prints an error message to the standard er‐
           ror 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 reas‐
       signed.  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 AT snark.com>.

SEE ALSO
       csh(1), sh(1), stty(1), terminfo(3NCURSES), tty(4), terminfo(5), ttys(4), environ(7)

ncurses 6.4                                  2023-12-23                                      tset(1)