Enhancement request: please add `locale` to list of allowed \write18 binaries
mseven at telus.net
Thu Jul 28 07:31:02 CEST 2022
(I'm *not* a TeX Live maintainer, just a regular user)
> The `locale` tool reads no files, writes no files, takes no input, and
> outputs an extremely limited set of information derived *entirely*
> from environment variables.
I can confirm that the official documentation agrees with this. From the
$ man 1p locale
locale -- get locale-specific information
locale [-ck] name...
The locale utility shall conform to the Base Definitions
volume of POSIX.1-2017, Section 12.2, Utility Syntax Guide-
The following options shall be supported:
-a Write information about all available public lo-
cales. The available locales shall include POSIX,
representing the POSIX locale. The manner in
which the implementation determines what other
locales are available is implementation-defined.
-c Write the names of selected locale categories;
see the STDOUT section. The -c option increases
readability when more than one category is se-
lected (for example, via more than one keyword
name or via a category name). It is valid both
with and without the -k option.
-k Write the names and values of selected keywords.
The implementation may omit values for some key-
words; see the OPERANDS section.
-m Write names of available charmaps; see the Base
Definitions volume of POSIX.1-2017, Section 6.1,
Portable Character Set.
The following operand shall be supported:
name The name of a locale category as defined in the
Base Definitions volume of POSIX.1-2017, Chapter
7, Locale, the name of a keyword in a locale cat-
egory, or the reserved name charmap. The named
category or keyword shall be selected for output.
If a single name represents both a locale cate-
gory name and a keyword name in the current lo-
cale, the results are unspecified. Otherwise,
both category and keyword names can be specified
as name operands, in any sequence. It is imple-
mentation-defined whether any keyword values are
written for the categories LC_CTYPE and LC_COL-
The following environment variables shall affect the execu-
tion of locale:
LANG Provide a default value for the internationaliza-
tion variables that are unset or null. (See the
Base Definitions volume of POSIX.1-2017, Section
8.2, Internationalization Variables for the
precedence of internationalization variables used
to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the
values of all the other internationalization
LC_CTYPE Determine the locale for the interpretation of
sequences of bytes of text data as characters
(for example, single-byte as opposed to multi-
byte characters in arguments and input files).
Determine the locale that should be used to af-
fect the format and contents of diagnostic mes-
sages written to standard error.
NLSPATH Determine the location of message catalogs for
the processing of LC_MESSAGES.
The application shall ensure that the LANG, LC_*, and
NLSPATH environment variables specify the current locale
environment to be written out; they shall be used if the -a
option is not specified.
The LANG variable shall be written first using the format:
The LC_ALL variable shall be written last, using the first
format shown above. If it is not set, it shall be written
The standard error shall be used only for diagnostic mes-
The following exit values shall be returned:
0 All the requested information was found and output
>0 An error occurred.
CONSEQUENCES OF ERRORS
The following sections are informative.
So I agree that this command looks sufficiently safe to be in the
restricted \write18 list.
> This would be useful to guess a default language with `babel` or
A few general comments here:
1: "locale" is a POSIX command, so it should work with macOS, BSD, and
Linux. It will not work with Windows though. There are other commands
that you can use on Windows to get the current language; however, none
of them would be safe enough for restricted \write18. It wouldn't be too
hard to make a "safe" wrapper script for Windows, but this is of course
2: I don't think that this is a good idea. One of the key features of
TeX (and LaTeX) is that identical input files should produce identical
output across all systems. Guessing a default language like this would
break this guarantee, which is probably ill-advised. I think that a
better approach would be to issue a warning if a default language isn't
set. This avoids any issues with system dependency or "hidden" state.
3: This is already (roughly) possible with LuaTeX right now:
$ luatex --no-shell-escape '\relax'
This is LuaTeX, Version 1.15.0 (TeX Live 2022)
warning (pdf backend): no pages of output.
Transcript written on texput.log.
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