инициализация терминала (terminal initialization)
Имя (Name)
@TSET@, @RESET@ - terminal initialization
Синопсис (Synopsis)
@TSET@ [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping]
[terminal]
@RESET@ [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping]
[terminal]
Описание (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.
Параметры (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 ('!').
История (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>.
Совместимость (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.
Окружение (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.
Файлы (Files)
/etc/ttys
system port name to terminal type mapping database (BSD
versions only).
@TERMINFO@
terminal capability database
Смотри также (See also)
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@).
