tset

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 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 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 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 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 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 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 .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 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 (“!”).

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 development 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 reset.  Rather than
       simply copying the existing program, in this merged version, tset used
       the termcap database to do additional (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(1) 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 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 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 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 looking for the terminal
            description.

FILES
       /etc/ttys
            system port name to terminal type mapping database (BSD versions
            only).

       /usr/share/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 20180127).



                                                                       tset(1)