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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

       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 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  descrip-
       tion 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  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.

       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 car-
           riage-return may no longer work in the abnormal state.

       o   Also, the terminal will often not echo the command.

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 the section TERMINAL TYPE MAP-
            PING for more information.

       -Q   Do  not  display  any values for the erase, interrupt and line kill characters.  Nor-
            mally 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 ini-
            tialized 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 ca-
       pabilities 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 .lo-
       gin 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 termi-
       nal 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 speci-
       fied, 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 1BSD (March 1978), 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.  That version of reset did  not
       use the termcap database.

       A  separate  tset command was provided in 1BSD by Eric Allman, using the termcap database.
       Allman's comments in the source code indicate that he began work in October 1977, continu-
       ing development over the next few years.

       According to comments in the source code, the tset program was modified in September 1980,
       to use logic copied from the 3BSD "reset" when it was invoked as reset.  This version  ap-
       peared 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  en-
       vironment by Eric S. Raymond <esr AT snark.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), presum-
       ably 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 ter-
       minfo-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  op-
       tion 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 interac-
       tion 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 win-
       dow 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 oper-
           ating 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 look-
            ing 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 6.3 (patch 20211021).

                                                                                          tset(1)

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