Provided by: ncurses-bin_6.5-2_amd64 bug

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
       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,

       •   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.

   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(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
       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(3NCURSES), which may be  from
           the  operating  system,  the  LINES  and COLUMNS environment variables or the terminal
           description.

       Obtaining  the  window  size  from  a  terminal's  type  description  is  common  to  both
       implementations,  but  considered  obsolescent.   Its  only  practical use is for hardware
       terminals.  Generally, the window size will remain uninitialized  only  if  there  were  a
       problem  obtaining  the  value from the operating system (and setupterm would still fail).
       The LINES and COLUMNS environment variables may thus be useful for working around  window-
       size  problems,  but have the drawback that if the window is resized, their values must be
       recomputed and reassigned.  The resize(1) program distributed with xterm(1)  assists  this
       activity.

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), terminfo(3NCURSES), tty(4), terminfo(5), ttys(4), environ(7)