1LUIT(1) General Commands Manual LUIT(1)
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6 luit - Locale and ISO 2022 support for Unicode terminals
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9 luit [ options ] [ -- ] [ program [ args ] ]
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12 Luit is a filter that can be run between an arbitrary application and a
13 UTF-8 terminal emulator. It will convert application output from the
14 locale's encoding into UTF-8, and convert terminal input from UTF-8
15 into the locale's encoding.
16 Luit reads its input from the child process, i.e., an application run‐
18 ning in the terminal. Luit writes its output to the terminal. The two
19 (input and output) can have different encodings.
20 An application may also request switching to a different output encod‐
22 ing using ISO 2022 and ISO 6429 escape sequences. Use of this feature
23 is discouraged: multilingual applications should be modified to di‐
24 rectly generate UTF-8 instead.
25 Luit is usually invoked transparently by the terminal emulator. For
27 information about running luit from the command line, see EXAMPLES be‐
28 low.
29
31 -V Print luit's version and quit.
32 -alias filename
34 the locale alias file
35 (default: unknown).
36 -argv0 name
38 Set the child's name (as passed in argv[0]).
39 -c Function as a simple converter from standard input to standard
41 output.
42 -encoding encoding
44 Set up luit to use encoding rather than the current locale's en‐
45 coding.
46 -g0 charset
48 Set the output charset initially selected in G0. The default
49 depends on the locale, but is usually ASCII.
50 -g1 charset
52 Set the output charset initially selected in G1. The default
53 depends on the locale.
54 -g2 charset
56 Set the output charset initially selected in G2. The default
57 depends on the locale.
58 -g3 charset
60 Set the output charset initially selected in G3. The default
61 depends on the locale.
62 -gl gn Set the initial assignment of GL in the output. The argument
64 should be one of g0, g1, g2 or g3. The default depends on the
65 locale, but is usually g0.
66 -gr gk Set the initial assignment of GR in the output. The default de‐
68 pends on the locale, and is usually g2 except for EUC locales,
69 where it is g1.
70 -h Display a usage and options message on the standard output and
72 quit.
73 -ilog filename
75 Log into filename all the bytes received from the child.
76 -k7 Generate seven-bit characters for keyboard input.
78 -kg0 charset
80 Set the input charset initially selected in G0. The default de‐
81 pends on the locale, but is usually ASCII.
82 -kg1 charset
84 Set the input charset initially selected in G1. The default de‐
85 pends on the locale.
86 -kg2 charset
88 Set the input charset initially selected in G2. The default de‐
89 pends on the locale.
90 -kg3 charset
92 Set the input charset initially selected in G3. The default de‐
93 pends on the locale.
94 -kgl gn
96 Set the initial assignment of GL in the input. The argument
97 should be one of g0, g1, g2 or g3. The default depends on the
98 locale, but is usually g0.
99 -kgr gk
101 Set the initial assignment of GR in the input. The default de‐
102 pends on the locale, and is usually g2 except for EUC locales,
103 where it is g1.
104 -kls Generate locking shifts (SO/SI) for keyboard input.
106 +kss Disable generation of single-shifts for keyboard input.
108 +kssgr Use GL codes after a single shift for keyboard input. By de‐
110 fault, GR codes are generated after a single shift when generat‐
111 ing eight-bit keyboard input.
112 -list List the supported charsets and encodings, then quit. Luit uses
114 its internal tables for this, which are based on the fontenc li‐
115 brary.
116 -list-builtin
118 List the built-in encodings used as a fallback when data from
119 iconv or fontenc is missing.
120 This option relies on luit being configured to use iconv, since
122 the fontenc library does not supply a list of built-in encod‐
123 ings.
124 -list-fontenc
126 List the encodings provided by “.enc” files originally distrib‐
127 uted with the fontenc library.
128 -list-iconv
130 List the encodings and locales supported by the iconv library.
131 Luit adapts its internal tables of fontenc names to iconv encod‐
132 ings.
133 To make scripting simpler, luit ignores spaces, underscores and
135 ASCII minus-signs (dash) embedded in the names. Luit also ig‐
136 nores case when matching charset and encoding names.
137 This option lists only the encodings which are associated with
139 the locales supported on the current operating system. The por‐
140 table iconv application provides a list of its supported encod‐
141 ings with the -l option. Other implementations may provide sim‐
142 ilar functionality. There is no portable library call by which
143 an application can obtain the same information.
144 -olog filename
146 Log into filename all the bytes sent to the terminal emulator.
147 +ols Disable interpretation of locking shifts in application output.
149 +osl Disable interpretation of character set selection sequences in
151 application output.
152 +oss Disable interpretation of single shifts in application output.
154 +ot Disable interpretation of all sequences and pass all sequences
156 in application output to the terminal unchanged. This may lead
157 to interesting results.
158 -p In startup, establish a handshake between parent and child pro‐
160 cesses. This is needed for some older systems, e.g., to suc‐
161 cessfully copy the terminal settings to the pseudo-terminal.
162 -prefer list
164 Set the lookup-order preference for character set information.
165 The parameter is a comma-separated list of keywords. The de‐
166 fault order (listing all keywords) is
167 fontenc,builtin,iconv,posix
169 The default order uses fontenc first because this allows luit to
171 start more rapidly (about 0.1 seconds) than using iconv for com‐
172 plex encodings such as eucJP. However, you may find that the
173 iconv implementation is more accurate or complete. In that
174 case, you can use the -show-iconv option to obtain a text file
175 which can be used as an encoding with the fontenc configuration.
176 This option relies on luit being configured to use iconv, since
178 the fontenc library does not provide this choice.
179 -show-builtin encoding
181 Show a built-in encoding, e.g., from a “.enc” file using the
182 “.enc” format.
183 This option relies on luit being configured to use iconv, since
185 the fontenc library does not supply a list of built-in encod‐
186 ings.
187 -show-fontenc encoding
189 Show a given encoding, e.g., from a “.enc” file using the “.enc”
190 format. If luit is configured to use the fontenc library, it
191 obtains the information using that library. Otherwise luit
192 reads the file directly.
193 Some of fontenc's encodings are built into the library. The
195 fontenc library uses those in preference to an external file.
196 Use the -show-builtin option to provide similar information when
197 luit is configured to use iconv.
198 -show-iconv encoding
200 Show a given encoding, using the “.enc” format. If luit is con‐
201 figured to use iconv, it obtains the information using that in‐
202 terface. If iconv cannot supply the information, luit may use a
203 built-in table.
204 -t Initialize luit using the locale and command-line options, but
206 do not open a pty connection. This option is used for testing
207 luit's configuration. It will exit with success if no errors
208 were detected. Repeat the -t option to cause warning messages
209 to be treated as errors.
210 -v Be verbose. Repeating the option, e.g., “-v -v” makes it more
212 verbose. Luit does not use getopt, so “-vv” does not work.
213 -x Exit as soon as the child dies. This may cause luit to lose
215 data at the end of the child's output.
216 -- End of options.
218
220 Luit uses these environment variables:
221 FONT_ENCODINGS_DIRECTORY
223 overrides the location of the “encodings.dir” file, which lists
224 encodings in external “.enc” files.
225 LC_ALL
227 LC_CTYPE
229 LANG During initialization, luit calls setlocale to check if the
231 user's locale is supported by the operating system. If setlo‐
232 cale returns a failure, luit looks instead at these variables in
233 succession to obtain any clues from the user's environment for
234 locale preference.
235 NCURSES_NO_UTF8_ACS
237 Luit sets this to tell ncurses to not rely upon VT100 SI/SO con‐
238 trols for line-drawing.
239 SHELL This is normally set by shells other than the Bourne shell, as a
241 convention. Luit will use this value (rather than the user's
242 entry in /etc/passwd) to decide which shell to execute. If
243 SHELL is not set, luit executes /bin/sh.
244
246 The most typical use of luit is to adapt an instance of XTerm to the
247 locale's encoding. Current versions of XTerm invoke luit automatically
248 when it is needed. If you are using an older release of XTerm, or a
249 different terminal emulator, you may invoke luit manually:
250 $ xterm -u8 -e luit
252 If you are running in a UTF-8 locale but need to access a remote ma‐
254 chine that doesn't support UTF-8, luit can adapt the remote output to
255 your terminal:
256 $ LC_ALL=fr_FR luit ssh legacy-machine
258 Luit is also useful with applications that hard-wire an encoding that
260 is different from the one normally used on the system or want to use
261 legacy escape sequences for multilingual output. In particular, ver‐
262 sions of Emacs that do not speak UTF-8 well can use luit for multilin‐
263 gual output:
264 $ luit -encoding 'ISO 8859-1' emacs -nw
266 And then, in Emacs,
268 M-x set-terminal-coding-system RET iso-2022-8bit-ss2 RET
270
272 unknown
273 The file mapping locales to locale encodings.
274
276 On systems with SVR4 (“Unix-98”) ptys (Linux version 2.2 and later,
277 SVR4), luit should be run as the invoking user.
278 On systems without SVR4 (“Unix-98”) ptys (notably BSD variants), run‐
280 ning luit as an ordinary user will leave the tty world-writable; this
281 is a security hole, and luit will generate a warning (but still accept
282 to run). A possible solution is to make luit suid root; luit should
283 drop privileges sufficiently early to make this safe. However, the
284 startup code has not been exhaustively audited, and the author takes no
285 responsibility for any resulting security issues.
286 Luit will refuse to run if it is installed setuid and cannot safely
288 drop privileges.
289
291 None of this complexity should be necessary. Stateless UTF-8 through‐
292 out the system is the way to go.
293 Charsets with a non-trivial intermediary byte are not yet supported.
295 Selecting alternate sets of control characters is not supported and
297 will never be.
298
300 These are portable:
301 • xterm(1),
303 • ncurses(1).
305 These are Linux-specific:
307 • unicode(1),
309 • utf-8(1),
311 • charsets(1).
313 These are particularly useful:
315 • Character Code Structure and Extension Techniques (ISO 2022, ECMA-35)
317 • Control Functions for Coded Character Sets (ISO 6429, ECMA-48)
319 • http://czyborra.com/charsets/
321
323 Luit was written by Juliusz Chroboczek <jch@pps.jussieu.fr> for the
324 XFree86 project.
325 Thomas E. Dickey has maintained luit for use by xterm since 2006.
327 X Window System LUIT(1)