https://invisible-island.net/luit/
luit - Locale and ISO 2022 support for Unicode terminals
luit [ options ] [ -- ] [ program [ args ] ]
Luit is a filter that can be run between an arbitrary application and a
UTF-8 terminal emulator. It will convert application output from the
locale's encoding into UTF-8, and convert terminal input from UTF-8
into the locale's encoding.
Luit reads its input from the child process, i.e., an application
running in the terminal. Luit writes its output to the terminal. The
two (input and output) can have different encodings.
An application may also request switching to a different output
encoding using ISO 2022 and ISO 6429 escape sequences. Use of this
feature is discouraged: multilingual applications should be modified to
directly generate UTF-8 instead.
Luit is usually invoked transparently by the terminal emulator. For
information about running luit from the command line, see EXAMPLES
below.
-V Print luit's version and quit.
-alias filename
the locale alias file
(default: ).
-argv0 name
Set the child's name (as passed in argv[0]).
-c Function as a simple converter from standard input to standard
output.
-encoding encoding
Set up luit to use encoding rather than the current locale's
encoding.
-g0 charset
Set the output charset initially selected in G0. The default
depends on the locale, but is usually ASCII.
-g1 charset
Set the output charset initially selected in G1. The default
depends on the locale.
-g2 charset
Set the output charset initially selected in G2. The default
depends on the locale.
-g3 charset
Set the output charset initially selected in G3. The default
depends on the locale.
-gl gn Set the initial assignment of GL in the output. The argument
should be one of g0, g1, g2 or g3. The default depends on the
locale, but is usually g0.
-gr gk Set the initial assignment of GR in the output. The default
depends on the locale, and is usually g2 except for EUC locales,
where it is g1.
-h Display a usage and options message on the standard output and
quit.
-ilog filename
Log into filename all the bytes received from the child.
-k7 Generate seven-bit characters for keyboard input.
-kg0 charset
Set the input charset initially selected in G0. The default
depends on the locale, but is usually ASCII.
-kg1 charset
Set the input charset initially selected in G1. The default
depends on the locale.
-kg2 charset
Set the input charset initially selected in G2. The default
depends on the locale.
-kg3 charset
Set the input charset initially selected in G3. The default
depends on the locale.
-kgl gn
Set the initial assignment of GL in the input. The argument
should be one of g0, g1, g2 or g3. The default depends on the
locale, but is usually g0.
-kgr gk
Set the initial assignment of GR in the input. The default
depends on the locale, and is usually g2 except for EUC locales,
where it is g1.
-kls Generate locking shifts (SO/SI) for keyboard input.
+kss Disable generation of single-shifts for keyboard input.
+kssgr Use GL codes after a single shift for keyboard input. By
default, GR codes are generated after a single shift when
generating eight-bit keyboard input.
-list List the supported charsets and encodings, then quit. Luit uses
its internal tables for this, which are based on the fontenc
library.
-list-builtin
List the built-in encodings used as a fallback when data from
iconv or fontenc is missing.
This option relies on luit being configured to use iconv, since
the fontenc library does not supply a list of built-in
encodings.
-list-fontenc
List the encodings provided by ".enc" files originally
distributed with the fontenc library.
-list-iconv
List the encodings and locales supported by the iconv library.
Luit adapts its internal tables of fontenc names to iconv
encodings.
To make scripting simpler, luit ignores spaces, underscores and
ASCII minus-signs (dash) embedded in the names. Luit also
ignores case when matching charset and encoding names.
This option lists only the encodings which are associated with
the locales supported on the current operating system. The
portable iconv application provides a list of its supported
encodings with the -l option. Other implementations may provide
similar functionality. There is no portable library call by
which an application can obtain the same information.
-olog filename
Log into filename all the bytes sent to the terminal emulator.
+ols Disable interpretation of locking shifts in application output.
+osl Disable interpretation of character set selection sequences in
application output.
+oss Disable interpretation of single shifts in application output.
+ot Disable interpretation of all sequences and pass all sequences
in application output to the terminal unchanged. This may lead
to interesting results.
-p In startup, establish a handshake between parent and child
processes. This is needed for some older systems, e.g., to
successfully copy the terminal settings to the pseudo-terminal.
-prefer list
Set the lookup-order preference for character set information.
The parameter is a comma-separated list of keywords. The
default order (listing all keywords) is
fontenc,builtin,iconv,posix
The default order uses fontenc first because this allows luit to
start more rapidly (about 0.1 seconds) than using iconv for
complex encodings such as eucJP. However, you may find that the
iconv implementation is more accurate or complete. In that
case, you can use the -show-iconv option to obtain a text file
which can be used as an encoding with the fontenc configuration.
This option relies on luit being configured to use iconv, since
the fontenc library does not provide this choice.
-show-builtin encoding
Show a built-in encoding, e.g., from a ".enc" file using the
".enc" format.
This option relies on luit being configured to use iconv, since
the fontenc library does not supply a list of built-in
encodings.
-show-fontenc encoding
Show a given encoding, e.g., from a ".enc" file using the ".enc"
format. If luit is configured to use the fontenc library, it
obtains the information using that library. Otherwise luit
reads the file directly.
Some of fontenc's encodings are built into the library. The
fontenc library uses those in preference to an external file.
Use the -show-builtin option to provide similar information when
luit is configured to use iconv.
-show-iconv encoding
Show a given encoding, using the ".enc" format. If luit is
configured to use iconv, it obtains the information using that
interface. If iconv cannot supply the information, luit may use
a built-in table.
-t Initialize luit using the locale and command-line options, but
do not open a pty connection. This option is used for testing
luit's configuration. It will exit with success if no errors
were detected. Repeat the -t option to cause warning messages
to be treated as errors.
-v Be verbose. Repeating the option, e.g., "-v -v" makes it more
verbose. Luit does not use getopt, so "-vv" does not work.
-x Exit as soon as the child dies. This may cause luit to lose
data at the end of the child's output.
-- End of options.
Luit uses these environment variables:
FONT_ENCODINGS_DIRECTORY
overrides the location of the "encodings.dir" file, which lists
encodings in external ".enc" files.
LC_ALL
LC_CTYPE
LANG During initialization, luit calls setlocale to check if the
user's locale is supported by the operating system. If
setlocale returns a failure, luit looks instead at these
variables in succession to obtain any clues from the user's
environment for locale preference.
NCURSES_NO_UTF8_ACS
Luit sets this to tell ncurses to not rely upon VT100 SI/SO
controls for line-drawing.
SHELL This is normally set by shells other than the Bourne shell, as a
convention. Luit will use this value (rather than the user's
entry in /etc/passwd) to decide which shell to execute. If
SHELL is not set, luit executes /bin/sh.
The file mapping locales to locale encodings.
None of this complexity should be necessary. Stateless UTF-8
throughout the system is the way to go.
Charsets with a non-trivial intermediary byte are not yet supported.
Selecting alternate sets of control characters is not supported and
will never be.
On systems with SVR4 ("Unix-98") ptys (Linux version 2.2 and later,
SVR4), luit should be run as the invoking user.
On systems without SVR4 ("Unix-98") ptys (notably BSD variants),
running luit as an ordinary user will leave the tty world-writable;
this is a security hole, and luit will generate a warning (but still
accept to run). A possible solution is to make luit suid root; luit
should drop privileges sufficiently early to make this safe. However,
the startup code has not been exhaustively audited, and the author
takes no responsibility for any resulting security issues.
Luit will refuse to run if it is installed setuid and cannot safely
drop privileges.
The most typical use of luit is to adapt an instance of XTerm to the
locale's encoding. Current versions of XTerm invoke luit automatically
when it is needed. If you are using an older release of XTerm, or a
different terminal emulator, you may invoke luit manually:
$ xterm -u8 -e luit
If you are running in a UTF-8 locale but need to access a remote
machine that doesn't support UTF-8, luit can adapt the remote output to
your terminal:
$ LC_ALL=fr_FR luit ssh legacy-machine
Luit is also useful with applications that hard-wire an encoding that
is different from the one normally used on the system or want to use
legacy escape sequences for multilingual output. In particular,
versions of Emacs that do not speak UTF-8 well can use luit for
multilingual output:
$ luit -encoding 'ISO 8859-1' emacs -nw
And then, in Emacs,
M-x set-terminal-coding-system RET iso-2022-8bit-ss2 RET
Luit was written by Juliusz Chroboczek <jch@pps.jussieu.fr> for the
XFree86 project.
Thomas E. Dickey has maintained luit for use by xterm since 2006.
These are portable:
o xterm(1),
o ncurses(3X).
These are Linux-specific:
o unicode(7),
o utf-8(7),
o charsets(7).
These are particularly useful:
o Character Code Structure and Extension Techniques (ISO 2022, ECMA-35)
o Control Functions for Coded Character Sets (ISO 6429, ECMA-48)
o https://czyborra.com/charsets/
X Window System LUIT(1)