tset 1 2024-06-08 ncurses 6.5 User commands

tset(1)                          User commands                         tset(1)


       tset, reset - initialize or reset terminal state


       tset  [-IQVcqrsw]  [-]  [-e ch] [-i ch] [-k ch] [-m mapping] [terminal-
       reset [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m  mapping]  [terminal-


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 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

       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,

       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  description  (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,
           if  the  terminal device does not appear to be a pseudoterminal (as
           might be used by a  terminal  emulator  program),  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


           (the line-feed character is normally control-J) to get the terminal
           to  work,  as  carriage-return  may  no longer work in the abnormal

       o   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 ("!").


       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

       -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

       -V   reports the version of ncurses which was used in this program, and

       -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.


       The tset command uses these environment variables:

            tells  tset  whether  to  initialize  TERM  using  sh(1) or csh(1)

       TERM Denotes your terminal  type.   Each  terminal  type  is  distinct,
            though many are similar.

            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


              system port name to terminal type mapping database (BSD versions

              compiled terminal description database directory


       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

       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:

       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

       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.

       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(3x), 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.


       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 <>.


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

ncurses 6.5                       2024-06-08                           tset(1)