tset(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SETTING THE ENVIRONMENT | TERMINAL TYPE MAPPING | HISTORY | COMPATIBILITY | ENVIRONMENT | FILES | SEE ALSO | COLOPHON

@TSET@(1)                General Commands Manual               @TSET@(1)

NAME         top

       @TSET@, @RESET@ - terminal initialization

SYNOPSIS         top

       @TSET@ [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping]
       [terminal]
       @RESET@ [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping]
       [terminal]

DESCRIPTION         top

   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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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         top

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

       @TERMINFO@
            terminal capability database

SEE ALSO         top

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

       This describes ncurses version @NCURSES_MAJOR@.@NCURSES_MINOR@
       (patch @NCURSES_PATCH@).

COLOPHON         top

       This page is part of the ncurses (new curses) project.
       Information about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have
       a bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
       project's upstream Git mirror of the CVS repository
       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2021-08-27.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-05-23.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

                                                               @TSET@(1)

Pages that refer to this page: termios(3)ttytype(5)