LUIT(1) General Commands Manual LUIT(1)
NAME
luit - Locale and ISO 2022 support for Unicode terminals
SYNOPSIS
luit [ options ] [ -- ] [ program [ args ] ]
DESCRIPTION
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 run-
ning 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 in-
formation about running luit from the command line, see EXAMPLES below.
OPTIONS
-V Print luit's version and quit.
-alias filename
the locale alias file
(default: unknown).
-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 en-
coding.
-g0 charset
Set the output charset initially selected in G0. The default de-
pends on the locale, but is usually ASCII.
-g1 charset
Set the output charset initially selected in G1. The default de-
pends on the locale.
-g2 charset
Set the output charset initially selected in G2. The default de-
pends on the locale.
-g3 charset
Set the output charset initially selected in G3. The default de-
pends 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 de-
pends 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 de-
pends on the locale, but is usually ASCII.
-kg1 charset
Set the input charset initially selected in G1. The default de-
pends on the locale.
-kg2 charset
Set the input charset initially selected in G2. The default de-
pends on the locale.
-kg3 charset
Set the input charset initially selected in G3. The default de-
pends 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 de-
pends 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 de-
fault, GR codes are generated after a single shift when generat-
ing 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 li-
brary.
-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 distrib-
uted 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 encod-
ings.
To make scripting simpler, luit ignores spaces, underscores and
ASCII minus-signs (dash) embedded in the names. Luit also ig-
nores 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 en-
codings 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 suc-
cessfully 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 com-
plex 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 ob-
tains 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 con-
figured to use iconv, it obtains the information using that in-
terface. 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.
ENVIRONMENT
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 suc-
cession to obtain any clues from the user's environment for lo-
cale preference.
NCURSES_NO_UTF8_ACS
Luit sets this to tell ncurses to not rely upon VT100 SI/SO con-
trols 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 en-
try in /etc/passwd) to decide which shell to execute. If SHELL
is not set, luit executes /bin/sh.
FILES
unknown
The file mapping locales to locale encodings.
BUGS
Limitations
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.
Security
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 respon-
sibility for any resulting security issues.
Luit will refuse to run if it is installed setuid and cannot safely drop
privileges.
EXAMPLES
The most typical use of luit is to adapt an instance of XTerm to the lo-
cale'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
AUTHORS
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.
SEE ALSO
These are portable:
• xterm(1),
• ncurses(3X).
These are Linux-specific:
• unicode(1),
• utf-8(1),
• charsets(1).
These are particularly useful:
• Character Code Structure and Extension Techniques (ISO 2022, ECMA-35)
• Control Functions for Coded Character Sets (ISO 6429, ECMA-48)
• http://czyborra.com/charsets/
X Window System LUIT(1)
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