tset(1) User commands tset(1) #
tset(1) User commands tset(1)
NNAAMMEE #
ttsseett, ?? - terminal initialization
SSYYNNOOPPSSIISS #
ttsseett [--IIQQVVccqqrrssww] [--] [--ee _c_h] [--ii _c_h] [--kk _c_h] [--mm _m_a_p_p_i_n_g] [_t_e_r_m_i_n_a_l]
?? [--IIQQVVccqqrrssww] [--] [--ee _c_h] [--ii _c_h] [--kk _c_h] [--mm _m_a_p_p_i_n_g] [_t_e_r_m_i_n_a_l]
DDEESSCCRRIIPPTTIIOONN #
ttsseett -- iinniittiiaalliizzaattiioonn This program initializes terminals.
First, ttsseett 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, ttsseett
remembers which file descriptor to use when updating settings.
Next, ttsseett determines the type of terminal that you are using. This
determination is done as follows, using the first terminal type found.
1. The tteerrmmiinnaall argument specified on the command line.
2. The value of the TTEERRMM environmental variable.
3. (BSD systems only.) The terminal type associated with the standard
error output device in the _/_e_t_c_/_t_t_y_s file. (On System-V-like UNIXes and
systems using that convention, ggeettttyy(1) does this job by setting TTEERRMM
according to the type passed to it by _/_e_t_c_/_i_n_i_t_t_a_b.)
4. The default terminal type, “unknown”, is not suitable for curses
applications.
If the terminal type was not specified on the command-line, the --mm option
mappings are then applied (see the section TTEERRMMIINNAALL TTYYPPEE MMAAPPPPIINNGG 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 “--ww” option is enabled, ttsseett 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., LLIINNEESS and CCOOLLUUMMNNSS
variables specify this), use this to set the operating system's
notion of the window size.
• if the “--cc” option is enabled, the backspace, interrupt and line kill
characters (among many other things) are set
• unless the “--II” option is enabled, the terminal and tab
_i_n_i_t_i_a_l_i_z_a_t_i_o_n strings are sent to the standard error output, and
ttsseett 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.
rreesseett -- rreeiinniittiiaalliizzaattiioonn When invoked as ??, ttsseett 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 _i_n_i_t_i_a_l_i_z_a_t_i_o_n strings, it uses the terminal
_r_e_s_e_t strings.
The ?? command is useful after a program dies leaving a terminal in an
abnormal state:
• you may have to type
_<_L_F_>??_<_L_F_> #
(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.
OOPPTTIIOONNSS #
The options are as follows:
--cc Set control characters and modes.
--ee _c_h
Set the erase character to _c_h.
--II Do not send the terminal or tab initialization strings to the
terminal.
--ii _c_h
Set the interrupt character to _c_h.
--kk _c_h
Set the line kill character to _c_h.
--mm _m_a_p_p_i_n_g
Specify a mapping from a port type to a terminal. See the section
TTEERRMMIINNAALL TTYYPPEE MMAAPPPPIINNGG for more information.
--QQ Do not display any values for the erase, interrupt and line kill
characters. Normally ttsseett displays the values for control
characters which differ from the system's default values.
--qq 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.
--rr Print the terminal type to the standard error output.
--ss Print the sequence of shell commands to initialize the environment
variable TTEERRMM to the standard output. See the section SSEETTTTIINNGG TTHHEE
EENNVVIIRROONNMMEENNTT for details.
--VV reports the version of ncurses which was used in this program, and
exits.
--ww Resize the window to match the size deduced via sseettuupptteerrmm(3).
Normally this has no effect, unless sseettuupptteerrmm is not able to detect
the window size.
The arguments for the --ee, --ii, and --kk 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 --cc or --ww is given, both options are assumed.
SSEETTTTIINNGG TTHHEE EENNVVIIRROONNMMEENNTT #
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 --ss option.
When the --ss option is specified, the commands to enter the information
into the shell's environment are written to the standard output. If the
SSHHEELLLL environmental variable ends in “csh”, the commands are for ccsshh,
otherwise, they are for sshh(1). Note, the ccsshh commands set and unset the
shell variable nnoogglloobb, leaving it unset. The following line in the
..llooggiinn or ..pprrooffiillee files will initialize the environment correctly:
eval `tset -s options ... `
TTEERRMMIINNAALL TTYYPPEE MMAAPPPPIINNGG #
When the terminal is not hardwired into the system (or the current system
information is incorrect) the terminal type derived from the _/_e_t_c_/_t_t_y_s
file or the TTEERRMM environmental variable is often something generic like
nneettwwoorrkk, ddiiaalluupp, or uunnkknnoowwnn. When ttsseett is used in a startup script it is
often desirable to provide information about the type of terminal used on
such ports.
The --mm options maps from some set of conditions to a terminal type, that
is, to tell ttsseett “If I'm on this port at a particular speed, guess that
I'm on that kind of terminal”.
The argument to the --mm 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 --mm
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: ddiiaalluupp>>99660000::vvtt110000. 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 ddiiaalluupp, and the baud rate is greater than
9600 baud, a terminal type of vvtt110000 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, --mm ddiiaalluupp::vvtt110000 --mm ::??xxtteerrmm 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 --mm option argument. Also,
to avoid problems with meta-characters, it is suggested that the entire
--mm option argument be placed within single quote characters, and that ccsshh
users insert a backslash character (“\”) before any exclamation marks
(“!”).
HHIISSTTOORRYY #
A rreesseett command appeared in 1BSD (March 1978), written by Kurt Shoens.
This program set the _e_r_a_s_e and _k_i_l_l characters to ^^HH (backspace) and @@
respectively. Mark Horton improved that in 3BSD (October 1979), adding
_i_n_t_r, _q_u_i_t, _s_t_a_r_t/_s_t_o_p and _e_o_f characters as well as changing the program
to avoid modifying any user settings. That version of rreesseett did not use
the termcap database.
A separate ttsseett 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, continuing development over the next few
years.
According to comments in the source code, the ttsseett program was modified
in September 1980, to use logic copied from the 3BSD “reset” when it was
invoked as rreesseett. This version appeared in 4.1cBSD, late in 1982.
Other developers (e.g., Keith Bostic and Jim Bloom) continued to modify
ttsseett until 4.4BSD was released in 1993.
The nnccuurrsseess implementation was lightly adapted from the 4.4BSD sources
for a terminfo environment by Eric S. Raymond <esr@snark.thyrsus.com>.
CCOOMMPPAATTIIBBIILLIITTYY #
Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
(POSIX.1-2008) nor X/Open Curses Issue 7 documents ttsseett or ??.
The AT&T ttppuutt utility (AIX, HPUX, Solaris) incorporated the terminal-mode
manipulation as well as termcap-based features such as resetting tabstops
from ttsseett in BSD (4.1c), presumably with the intention of making ttsseett
obsolete. However, each of those systems still provides ttsseett. In fact,
the commonly-used rreesseett utility is always an alias for ttsseett.
The ttsseett utility provides for backward-compatibility with BSD
environments (under most modern UNIXes, //eettcc//iinniittttaabb and ggeettttyy(1) can set
TTEERRMM appropriately for each dial-up line; this obviates what was ttsseett's
most important use). This implementation behaves like 4.4BSD ttsseett, with
a few exceptions specified here.
A few options are different because the TTEERRMMCCAAPP variable is no longer
supported under terminfo-based nnccuurrsseess:
• The --SS option of BSD ttsseett no longer works; it prints an error message
to the standard error and dies.
• The --ss option only sets TTEERRMM, not TTEERRMMCCAAPP.
There was an undocumented 4.4BSD feature that invoking ttsseett 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 --AA, --EE, --hh, --uu and --vv options were deleted from the ttsseett utility in
4.4BSD. None of them were documented in 4.3BSD and all are of limited
utility at best. The --aa, --dd, and --pp 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 --mm option instead. The --aa, --dd, and --pp 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 ttsseett provided a --nn 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 --ee, --ii, and --kk options without
arguments, although it is strongly recommended that such usage be fixed
to explicitly specify the character.
As of 4.4BSD, executing ttsseett as ?? no longer implies the --QQ option. Also,
the interaction between the - option and the _t_e_r_m_i_n_a_l argument in some
historic implementations of ttsseett has been removed.
The --cc and --ww options are not found in earlier implementations. However,
a different window size-change feature was provided in 4.4BSD.
• In 4.4BSD, ttsseett uses the window size from the termcap description to
set the window size if ttsseett is not able to obtain the window size
from the operating system.
• In ncurses, ttsseett obtains the window size using sseettuupptteerrmm, which may
be from the operating system, the LLIINNEESS and CCOOLLUUMMNNSS 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 sseettuupptteerrmm would still fail). For that reason, the LLIINNEESS and
CCOOLLUUMMNNSS 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 rreessiizzee(1) program.
EENNVVIIRROONNMMEENNTT #
The ttsseett command uses these environment variables:
SHELL #
tells ttsseett whether to initialize TTEERRMM using sshh(1) or ccsshh(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 “/”, ttsseett removes the
variable from the environment before looking for the terminal
description.
FFIILLEESS #
/etc/ttys
system port name to terminal type mapping database (BSD versions
only).
/usr/share/terminfo
terminal capability database
SSEEEE AALLSSOO #
ccsshh(1), sshh(1), ssttttyy(1), tteerrmmiinnffoo(3), ttttyy(4), tteerrmmiinnffoo(5), ttttyyss(5),
eennvviirroonn(7)
This describes nnccuurrsseess version 6.4 (patch 20230826).
ncurses 6.4 2023-07-01 tset(1)