mirror of
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709fbd3ec3
The mergesort removal from qsort implementation (commit 03bf8357e8
)
had the side-effect of making sorting nonstable. Although neither
POSIX nor C standard specify that qsort should be stable, it seems
that it has become an instance of Hyrum's law where multiple programs
expect it.
Also, the resulting introsort implementation is not faster than
the previous mergesort (which makes the change even less appealing).
This patch restores the previous mergesort implementation, with the
exception of machinery that checks the resulting allocation against
the _SC_PHYS_PAGES (it only adds complexity and the heuristic not
always make sense depending on the system configuration and load).
The alloca usage was replaced with a fixed-size buffer.
For the fallback mechanism, the implementation uses heapsort. It is
simpler than quicksort, and it does not suffer from adversarial
inputs. With memory overcommit, it should be rarely triggered.
The drawback is mergesort requires O(n) extra space, and since it is
allocated with malloc the function is AS-signal-unsafe. It should be
feasible to change it to use mmap, although I am not sure how urgent
it is. The heapsort is also nonstable, so programs that require a
stable sort would still be subject to this latent issue.
The tst-qsort5 is removed since it will not create quicksort adversarial
inputs with the current qsort_r implementation.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
1483 lines
58 KiB
Plaintext
1483 lines
58 KiB
Plaintext
@node Locales, Message Translation, Character Set Handling, Top
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@c %MENU% The country and language can affect the behavior of library functions
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@chapter Locales and Internationalization
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Different countries and cultures have varying conventions for how to
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communicate. These conventions range from very simple ones, such as the
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format for representing dates and times, to very complex ones, such as
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the language spoken.
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@cindex internationalization
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@cindex locales
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@dfn{Internationalization} of software means programming it to be able
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to adapt to the user's favorite conventions. In @w{ISO C},
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internationalization works by means of @dfn{locales}. Each locale
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specifies a collection of conventions, one convention for each purpose.
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The user chooses a set of conventions by specifying a locale (via
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environment variables).
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All programs inherit the chosen locale as part of their environment.
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Provided the programs are written to obey the choice of locale, they
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will follow the conventions preferred by the user.
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@menu
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* Effects of Locale:: Actions affected by the choice of
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locale.
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* Choosing Locale:: How the user specifies a locale.
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* Locale Categories:: Different purposes for which you can
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select a locale.
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* Setting the Locale:: How a program specifies the locale
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with library functions.
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* Standard Locales:: Locale names available on all systems.
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* Locale Names:: Format of system-specific locale names.
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* Locale Information:: How to access the information for the locale.
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* Formatting Numbers:: A dedicated function to format numbers.
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* Yes-or-No Questions:: Check a Response against the locale.
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@end menu
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@node Effects of Locale, Choosing Locale, , Locales
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@section What Effects a Locale Has
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Each locale specifies conventions for several purposes, including the
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following:
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@itemize @bullet
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@item
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What multibyte character sequences are valid, and how they are
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interpreted (@pxref{Character Set Handling}).
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@item
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Classification of which characters in the local character set are
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considered alphabetic, and upper- and lower-case conversion conventions
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(@pxref{Character Handling}).
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@item
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The collating sequence for the local language and character set
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(@pxref{Collation Functions}).
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@item
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Formatting of numbers and currency amounts (@pxref{General Numeric}).
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@item
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Formatting of dates and times (@pxref{Formatting Calendar Time}).
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@item
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What language to use for output, including error messages
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(@pxref{Message Translation}).
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@item
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What language to use for user answers to yes-or-no questions
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(@pxref{Yes-or-No Questions}).
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@item
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What language to use for more complex user input.
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(The C library doesn't yet help you implement this.)
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@end itemize
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Some aspects of adapting to the specified locale are handled
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automatically by the library subroutines. For example, all your program
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needs to do in order to use the collating sequence of the chosen locale
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is to use @code{strcoll} or @code{strxfrm} to compare strings.
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Other aspects of locales are beyond the comprehension of the library.
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For example, the library can't automatically translate your program's
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output messages into other languages. The only way you can support
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output in the user's favorite language is to program this more or less
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by hand. The C library provides functions to handle translations for
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multiple languages easily.
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This chapter discusses the mechanism by which you can modify the current
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locale. The effects of the current locale on specific library functions
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are discussed in more detail in the descriptions of those functions.
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@node Choosing Locale, Locale Categories, Effects of Locale, Locales
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@section Choosing a Locale
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The simplest way for the user to choose a locale is to set the
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environment variable @code{LANG}. This specifies a single locale to use
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for all purposes. For example, a user could specify a hypothetical
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locale named @samp{espana-castellano} to use the standard conventions of
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most of Spain.
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The set of locales supported depends on the operating system you are
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using, and so do their names, except that the standard locale called
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@samp{C} or @samp{POSIX} always exist. @xref{Locale Names}.
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In order to force the system to always use the default locale, the
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user can set the @code{LC_ALL} environment variable to @samp{C}.
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@cindex combining locales
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A user also has the option of specifying different locales for
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different purposes---in effect, choosing a mixture of multiple
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locales. @xref{Locale Categories}.
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For example, the user might specify the locale @samp{espana-castellano}
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for most purposes, but specify the locale @samp{usa-english} for
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currency formatting. This might make sense if the user is a
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Spanish-speaking American, working in Spanish, but representing monetary
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amounts in US dollars.
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Note that both locales @samp{espana-castellano} and @samp{usa-english},
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like all locales, would include conventions for all of the purposes to
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which locales apply. However, the user can choose to use each locale
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for a particular subset of those purposes.
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@node Locale Categories, Setting the Locale, Choosing Locale, Locales
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@section Locale Categories
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@cindex categories for locales
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@cindex locale categories
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The purposes that locales serve are grouped into @dfn{categories}, so
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that a user or a program can choose the locale for each category
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independently. Here is a table of categories; each name is both an
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environment variable that a user can set, and a macro name that you can
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use as the first argument to @code{setlocale}.
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The contents of the environment variable (or the string in the second
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argument to @code{setlocale}) has to be a valid locale name.
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@xref{Locale Names}.
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@vtable @code
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@item LC_COLLATE
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@standards{ISO, locale.h}
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This category applies to collation of strings (functions @code{strcoll}
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and @code{strxfrm}); see @ref{Collation Functions}.
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@item LC_CTYPE
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@standards{ISO, locale.h}
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This category applies to classification and conversion of characters,
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and to multibyte and wide characters;
|
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see @ref{Character Handling}, and @ref{Character Set Handling}.
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@item LC_MONETARY
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@standards{ISO, locale.h}
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This category applies to formatting monetary values; see @ref{General Numeric}.
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@item LC_NUMERIC
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@standards{ISO, locale.h}
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This category applies to formatting numeric values that are not
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monetary; see @ref{General Numeric}.
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@item LC_TIME
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@standards{ISO, locale.h}
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This category applies to formatting date and time values; see
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@ref{Formatting Calendar Time}.
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@item LC_MESSAGES
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@standards{XOPEN, locale.h}
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This category applies to selecting the language used in the user
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|
interface for message translation (@pxref{The Uniforum approach};
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@pxref{Message catalogs a la X/Open}) and contains regular expressions
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for affirmative and negative responses.
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@item LC_ALL
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@standards{ISO, locale.h}
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This is not a category; it is only a macro that you can use
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with @code{setlocale} to set a single locale for all purposes. Setting
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this environment variable overwrites all selections by the other
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@code{LC_*} variables or @code{LANG}.
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@item LANG
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@standards{ISO, locale.h}
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If this environment variable is defined, its value specifies the locale
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to use for all purposes except as overridden by the variables above.
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@end vtable
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@vindex LANGUAGE
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When developing the message translation functions it was felt that the
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functionality provided by the variables above is not sufficient. For
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example, it should be possible to specify more than one locale name.
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Take a Swedish user who better speaks German than English, and a program
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whose messages are output in English by default. It should be possible
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to specify that the first choice of language is Swedish, the second
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German, and if this also fails to use English. This is
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possible with the variable @code{LANGUAGE}. For further description of
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this GNU extension see @ref{Using gettextized software}.
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@node Setting the Locale, Standard Locales, Locale Categories, Locales
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@section How Programs Set the Locale
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A C program inherits its locale environment variables when it starts up.
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This happens automatically. However, these variables do not
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automatically control the locale used by the library functions, because
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@w{ISO C} says that all programs start by default in the standard @samp{C}
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locale. To use the locales specified by the environment, you must call
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@code{setlocale}. Call it as follows:
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@smallexample
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setlocale (LC_ALL, "");
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@end smallexample
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@noindent
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to select a locale based on the user choice of the appropriate
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environment variables.
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@cindex changing the locale
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@cindex locale, changing
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You can also use @code{setlocale} to specify a particular locale, for
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general use or for a specific category.
|
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@pindex locale.h
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The symbols in this section are defined in the header file @file{locale.h}.
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@deftypefun {char *} setlocale (int @var{category}, const char *@var{locale})
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@standards{ISO, locale.h}
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@safety{@prelim{}@mtunsafe{@mtasuconst{:@mtslocale{}} @mtsenv{}}@asunsafe{@asuinit{} @asulock{} @ascuheap{} @asucorrupt{}}@acunsafe{@acuinit{} @acucorrupt{} @aculock{} @acsmem{} @acsfd{}}}
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@c Uses of the global locale object are unguarded in functions that
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@c ought to be MT-Safe, so we're ruling out the use of this function
|
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@c once threads are started. It takes a write lock itself, but it may
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|
@c return a pointer loaded from the global locale object after releasing
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@c the lock, or before taking it.
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@c setlocale @mtasuconst:@mtslocale @mtsenv @asuinit @ascuheap @asulock @asucorrupt @acucorrupt @acsmem @acsfd @aculock
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@c libc_rwlock_wrlock @asulock @aculock
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@c libc_rwlock_unlock @aculock
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@c getenv LOCPATH @mtsenv
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@c malloc @ascuheap @acsmem
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@c free @ascuheap @acsmem
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@c new_composite_name ok
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|
@c setdata ok
|
|
@c setname ok
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|
@c _nl_find_locale @mtsenv @asuinit @ascuheap @asulock @asucorrupt @acucorrupt @acsmem @acsfd @aculock
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@c getenv LC_ALL and LANG @mtsenv
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@c _nl_load_locale_from_archive @ascuheap @acucorrupt @acsmem @acsfd
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@c sysconf _SC_PAGE_SIZE ok
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|
@c _nl_normalize_codeset @ascuheap @acsmem
|
|
@c isalnum_l ok (C locale)
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|
@c isdigit_l ok (C locale)
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|
@c malloc @ascuheap @acsmem
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@c tolower_l ok (C locale)
|
|
@c open_not_cancel_2 @acsfd
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|
@c fxstat64 ok
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|
@c close_not_cancel_no_status ok
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@c __mmap64 @acsmem
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@c calculate_head_size ok
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|
@c __munmap ok
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@c compute_hashval ok
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@c qsort dup @acucorrupt
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@c rangecmp ok
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@c malloc @ascuheap @acsmem
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@c strdup @ascuheap @acsmem
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|
@c _nl_intern_locale_data @ascuheap @acsmem
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@c malloc @ascuheap @acsmem
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@c free @ascuheap @acsmem
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@c _nl_expand_alias @ascuheap @asulock @acsmem @acsfd @aculock
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@c libc_lock_lock @asulock @aculock
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@c bsearch ok
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|
@c alias_compare ok
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@c strcasecmp ok
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|
@c read_alias_file @ascuheap @asulock @acsmem @acsfd @aculock
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|
@c fopen @ascuheap @asulock @acsmem @acsfd @aculock
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@c fsetlocking ok
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|
@c feof_unlocked ok
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|
@c fgets_unlocked ok
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|
@c isspace ok (locale mutex is locked)
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|
@c extend_alias_table @ascuheap @acsmem
|
|
@c realloc @ascuheap @acsmem
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|
@c realloc @ascuheap @acsmem
|
|
@c fclose @ascuheap @asulock @acsmem @acsfd @aculock
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@c alias_compare dup
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@c libc_lock_unlock @aculock
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|
@c _nl_explode_name @ascuheap @acsmem
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|
@c _nl_find_language ok
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|
@c _nl_normalize_codeset dup @ascuheap @acsmem
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|
@c _nl_make_l10nflist @ascuheap @acsmem
|
|
@c malloc @ascuheap @acsmem
|
|
@c free @ascuheap @acsmem
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|
@c __argz_stringify ok
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|
@c __argz_count ok
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|
@c __argz_next ok
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|
@c _nl_load_locale @ascuheap @acsmem @acsfd
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@c open_not_cancel_2 @acsfd
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@c __fxstat64 ok
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@c close_not_cancel_no_status ok
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@c mmap @acsmem
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@c malloc @ascuheap @acsmem
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@c read_not_cancel ok
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@c free @ascuheap @acsmem
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@c _nl_intern_locale_data dup @ascuheap @acsmem
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@c munmap ok
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@c __gconv_compare_alias @asuinit @ascuheap @asucorrupt @asulock @acsmem@acucorrupt @acsfd @aculock
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@c __gconv_read_conf @asuinit @ascuheap @asucorrupt @asulock @acsmem@acucorrupt @acsfd @aculock
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@c (libc_once-initializes gconv_cache and gconv_path_envvar; they're
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@c never modified afterwards)
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|
@c __gconv_load_cache @ascuheap @acsmem @acsfd
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@c getenv GCONV_PATH @mtsenv
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@c open_not_cancel @acsfd
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@c __fxstat64 ok
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|
@c close_not_cancel_no_status ok
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|
@c mmap @acsmem
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|
@c malloc @ascuheap @acsmem
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|
@c __read ok
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|
@c free @ascuheap @acsmem
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|
@c munmap ok
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|
@c __gconv_get_path @asulock @ascuheap @aculock @acsmem @acsfd
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|
@c getcwd @ascuheap @acsmem @acsfd
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|
@c libc_lock_lock @asulock @aculock
|
|
@c malloc @ascuheap @acsmem
|
|
@c strtok_r ok
|
|
@c libc_lock_unlock @aculock
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|
@c read_conf_file @ascuheap @asucorrupt @asulock @acsmem @acucorrupt @acsfd @aculock
|
|
@c fopen @ascuheap @asulock @acsmem @acsfd @aculock
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|
@c fsetlocking ok
|
|
@c feof_unlocked ok
|
|
@c getdelim @ascuheap @asucorrupt @acsmem @acucorrupt
|
|
@c isspace_l ok (C locale)
|
|
@c add_alias
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|
@c isspace_l ok (C locale)
|
|
@c toupper_l ok (C locale)
|
|
@c add_alias2 dup @ascuheap @acucorrupt @acsmem
|
|
@c add_module @ascuheap @acsmem
|
|
@c isspace_l ok (C locale)
|
|
@c toupper_l ok (C locale)
|
|
@c strtol ok (@mtslocale but we hold the locale lock)
|
|
@c tfind __gconv_alias_db ok
|
|
@c __gconv_alias_compare dup ok
|
|
@c calloc @ascuheap @acsmem
|
|
@c insert_module dup @ascuheap
|
|
@c __tfind ok (because the tree is read only by then)
|
|
@c __gconv_alias_compare dup ok
|
|
@c insert_module @ascuheap
|
|
@c free @ascuheap
|
|
@c add_alias2 @ascuheap @acucorrupt @acsmem
|
|
@c detect_conflict ok, reads __gconv_modules_db
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|
@c malloc @ascuheap @acsmem
|
|
@c tsearch __gconv_alias_db @ascuheap @acucorrupt @acsmem [exclusive tree, no @mtsrace]
|
|
@c __gconv_alias_compare ok
|
|
@c free @ascuheap
|
|
@c __gconv_compare_alias_cache ok
|
|
@c find_module_idx ok
|
|
@c do_lookup_alias ok
|
|
@c __tfind ok (because the tree is read only by then)
|
|
@c __gconv_alias_compare ok
|
|
@c strndup @ascuheap @acsmem
|
|
@c strcasecmp_l ok (C locale)
|
|
The function @code{setlocale} sets the current locale for category
|
|
@var{category} to @var{locale}.
|
|
|
|
If @var{category} is @code{LC_ALL}, this specifies the locale for all
|
|
purposes. The other possible values of @var{category} specify a
|
|
single purpose (@pxref{Locale Categories}).
|
|
|
|
You can also use this function to find out the current locale by passing
|
|
a null pointer as the @var{locale} argument. In this case,
|
|
@code{setlocale} returns a string that is the name of the locale
|
|
currently selected for category @var{category}.
|
|
|
|
The string returned by @code{setlocale} can be overwritten by subsequent
|
|
calls, so you should make a copy of the string (@pxref{Copying Strings
|
|
and Arrays}) if you want to save it past any further calls to
|
|
@code{setlocale}. (The standard library is guaranteed never to call
|
|
@code{setlocale} itself.)
|
|
|
|
You should not modify the string returned by @code{setlocale}. It might
|
|
be the same string that was passed as an argument in a previous call to
|
|
@code{setlocale}. One requirement is that the @var{category} must be
|
|
the same in the call the string was returned and the one when the string
|
|
is passed in as @var{locale} parameter.
|
|
|
|
When you read the current locale for category @code{LC_ALL}, the value
|
|
encodes the entire combination of selected locales for all categories.
|
|
If you specify the same ``locale name'' with @code{LC_ALL} in a
|
|
subsequent call to @code{setlocale}, it restores the same combination
|
|
of locale selections.
|
|
|
|
To be sure you can use the returned string encoding the currently selected
|
|
locale at a later time, you must make a copy of the string. It is not
|
|
guaranteed that the returned pointer remains valid over time.
|
|
|
|
When the @var{locale} argument is not a null pointer, the string returned
|
|
by @code{setlocale} reflects the newly-modified locale.
|
|
|
|
If you specify an empty string for @var{locale}, this means to read the
|
|
appropriate environment variable and use its value to select the locale
|
|
for @var{category}.
|
|
|
|
If a nonempty string is given for @var{locale}, then the locale of that
|
|
name is used if possible.
|
|
|
|
The effective locale name (either the second argument to
|
|
@code{setlocale}, or if the argument is an empty string, the name
|
|
obtained from the process environment) must be a valid locale name.
|
|
@xref{Locale Names}.
|
|
|
|
If you specify an invalid locale name, @code{setlocale} returns a null
|
|
pointer and leaves the current locale unchanged.
|
|
@end deftypefun
|
|
|
|
Here is an example showing how you might use @code{setlocale} to
|
|
temporarily switch to a new locale.
|
|
|
|
@smallexample
|
|
#include <stddef.h>
|
|
#include <locale.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
|
|
void
|
|
with_other_locale (char *new_locale,
|
|
void (*subroutine) (int),
|
|
int argument)
|
|
@{
|
|
char *old_locale, *saved_locale;
|
|
|
|
/* @r{Get the name of the current locale.} */
|
|
old_locale = setlocale (LC_ALL, NULL);
|
|
|
|
/* @r{Copy the name so it won't be clobbered by @code{setlocale}.} */
|
|
saved_locale = strdup (old_locale);
|
|
if (saved_locale == NULL)
|
|
fatal ("Out of memory");
|
|
|
|
/* @r{Now change the locale and do some stuff with it.} */
|
|
setlocale (LC_ALL, new_locale);
|
|
(*subroutine) (argument);
|
|
|
|
/* @r{Restore the original locale.} */
|
|
setlocale (LC_ALL, saved_locale);
|
|
free (saved_locale);
|
|
@}
|
|
@end smallexample
|
|
|
|
@strong{Portability Note:} Some @w{ISO C} systems may define additional
|
|
locale categories, and future versions of the library will do so. For
|
|
portability, assume that any symbol beginning with @samp{LC_} might be
|
|
defined in @file{locale.h}.
|
|
|
|
@node Standard Locales, Locale Names, Setting the Locale, Locales
|
|
@section Standard Locales
|
|
|
|
The only locale names you can count on finding on all operating systems
|
|
are these three standard ones:
|
|
|
|
@table @code
|
|
@item "C"
|
|
This is the standard C locale. The attributes and behavior it provides
|
|
are specified in the @w{ISO C} standard. When your program starts up, it
|
|
initially uses this locale by default.
|
|
|
|
@item "POSIX"
|
|
This is the standard POSIX locale. Currently, it is an alias for the
|
|
standard C locale.
|
|
|
|
@item ""
|
|
The empty name says to select a locale based on environment variables.
|
|
@xref{Locale Categories}.
|
|
@end table
|
|
|
|
Defining and installing named locales is normally a responsibility of
|
|
the system administrator at your site (or the person who installed
|
|
@theglibc{}). It is also possible for the user to create private
|
|
locales. All this will be discussed later when describing the tool to
|
|
do so.
|
|
@comment (@pxref{Building Locale Files}).
|
|
|
|
If your program needs to use something other than the @samp{C} locale,
|
|
it will be more portable if you use whatever locale the user specifies
|
|
with the environment, rather than trying to specify some non-standard
|
|
locale explicitly by name. Remember, different machines might have
|
|
different sets of locales installed.
|
|
|
|
@node Locale Names, Locale Information, Standard Locales, Locales
|
|
@section Locale Names
|
|
|
|
The following command prints a list of locales supported by the
|
|
system:
|
|
|
|
@pindex locale
|
|
@smallexample
|
|
locale -a
|
|
@end smallexample
|
|
|
|
@strong{Portability Note:} With the notable exception of the standard
|
|
locale names @samp{C} and @samp{POSIX}, locale names are
|
|
system-specific.
|
|
|
|
Most locale names follow XPG syntax and consist of up to four parts:
|
|
|
|
@smallexample
|
|
@var{language}[_@var{territory}[.@var{codeset}]][@@@var{modifier}]
|
|
@end smallexample
|
|
|
|
Beside the first part, all of them are allowed to be missing. If the
|
|
full specified locale is not found, less specific ones are looked for.
|
|
The various parts will be stripped off, in the following order:
|
|
|
|
@enumerate
|
|
@item
|
|
codeset
|
|
@item
|
|
normalized codeset
|
|
@item
|
|
territory
|
|
@item
|
|
modifier
|
|
@end enumerate
|
|
|
|
For example, the locale name @samp{de_AT.iso885915@@euro} denotes a
|
|
German-language locale for use in Austria, using the ISO-8859-15
|
|
(Latin-9) character set, and with the Euro as the currency symbol.
|
|
|
|
In addition to locale names which follow XPG syntax, systems may
|
|
provide aliases such as @samp{german}. Both categories of names must
|
|
not contain the slash character @samp{/}.
|
|
|
|
If the locale name starts with a slash @samp{/}, it is treated as a
|
|
path relative to the configured locale directories; see @code{LOCPATH}
|
|
below. The specified path must not contain a component @samp{..}, or
|
|
the name is invalid, and @code{setlocale} will fail.
|
|
|
|
@strong{Portability Note:} POSIX suggests that if a locale name starts
|
|
with a slash @samp{/}, it is resolved as an absolute path. However,
|
|
@theglibc{} treats it as a relative path under the directories listed
|
|
in @code{LOCPATH} (or the default locale directory if @code{LOCPATH}
|
|
is unset).
|
|
|
|
Locale names which are longer than an implementation-defined limit are
|
|
invalid and cause @code{setlocale} to fail.
|
|
|
|
As a special case, locale names used with @code{LC_ALL} can combine
|
|
several locales, reflecting different locale settings for different
|
|
categories. For example, you might want to use a U.S. locale with ISO
|
|
A4 paper format, so you set @code{LANG} to @samp{en_US.UTF-8}, and
|
|
@code{LC_PAPER} to @samp{de_DE.UTF-8}. In this case, the
|
|
@code{LC_ALL}-style combined locale name is
|
|
|
|
@smallexample
|
|
LC_CTYPE=en_US.UTF-8;LC_TIME=en_US.UTF-8;LC_PAPER=de_DE.UTF-8;@dots{}
|
|
@end smallexample
|
|
|
|
followed by other category settings not shown here.
|
|
|
|
@vindex LOCPATH
|
|
The path used for finding locale data can be set using the
|
|
@code{LOCPATH} environment variable. This variable lists the
|
|
directories in which to search for locale definitions, separated by a
|
|
colon @samp{:}.
|
|
|
|
The default path for finding locale data is system specific. A typical
|
|
value for the @code{LOCPATH} default is:
|
|
|
|
@smallexample
|
|
/usr/share/locale
|
|
@end smallexample
|
|
|
|
The value of @code{LOCPATH} is ignored by privileged programs for
|
|
security reasons, and only the default directory is used.
|
|
|
|
@node Locale Information, Formatting Numbers, Locale Names, Locales
|
|
@section Accessing Locale Information
|
|
|
|
There are several ways to access locale information. The simplest
|
|
way is to let the C library itself do the work. Several of the
|
|
functions in this library implicitly access the locale data, and use
|
|
what information is provided by the currently selected locale. This is
|
|
how the locale model is meant to work normally.
|
|
|
|
As an example take the @code{strftime} function, which is meant to nicely
|
|
format date and time information (@pxref{Formatting Calendar Time}).
|
|
Part of the standard information contained in the @code{LC_TIME}
|
|
category is the names of the months. Instead of requiring the
|
|
programmer to take care of providing the translations the
|
|
@code{strftime} function does this all by itself. @code{%A}
|
|
in the format string is replaced by the appropriate weekday
|
|
name of the locale currently selected by @code{LC_TIME}. This is an
|
|
easy example, and wherever possible functions do things automatically
|
|
in this way.
|
|
|
|
But there are quite often situations when there is simply no function
|
|
to perform the task, or it is simply not possible to do the work
|
|
automatically. For these cases it is necessary to access the
|
|
information in the locale directly. To do this the C library provides
|
|
two functions: @code{localeconv} and @code{nl_langinfo}. The former is
|
|
part of @w{ISO C} and therefore portable, but has a brain-damaged
|
|
interface. The second is part of the Unix interface and is portable in
|
|
as far as the system follows the Unix standards.
|
|
|
|
@menu
|
|
* The Lame Way to Locale Data:: ISO C's @code{localeconv}.
|
|
* The Elegant and Fast Way:: X/Open's @code{nl_langinfo}.
|
|
@end menu
|
|
|
|
@node The Lame Way to Locale Data, The Elegant and Fast Way, ,Locale Information
|
|
@subsection @code{localeconv}: It is portable but @dots{}
|
|
|
|
Together with the @code{setlocale} function the @w{ISO C} people
|
|
invented the @code{localeconv} function. It is a masterpiece of poor
|
|
design. It is expensive to use, not extensible, and not generally
|
|
usable as it provides access to only @code{LC_MONETARY} and
|
|
@code{LC_NUMERIC} related information. Nevertheless, if it is
|
|
applicable to a given situation it should be used since it is very
|
|
portable. The function @code{strfmon} formats monetary amounts
|
|
according to the selected locale using this information.
|
|
@pindex locale.h
|
|
@cindex monetary value formatting
|
|
@cindex numeric value formatting
|
|
|
|
@deftypefun {struct lconv *} localeconv (void)
|
|
@standards{ISO, locale.h}
|
|
@safety{@prelim{}@mtunsafe{@mtasurace{:localeconv} @mtslocale{}}@asunsafe{}@acsafe{}}
|
|
@c This function reads from multiple components of the locale object,
|
|
@c without synchronization, while writing to the static buffer it uses
|
|
@c as the return value.
|
|
The @code{localeconv} function returns a pointer to a structure whose
|
|
components contain information about how numeric and monetary values
|
|
should be formatted in the current locale.
|
|
|
|
You should not modify the structure or its contents. The structure might
|
|
be overwritten by subsequent calls to @code{localeconv}, or by calls to
|
|
@code{setlocale}, but no other function in the library overwrites this
|
|
value.
|
|
@end deftypefun
|
|
|
|
@deftp {Data Type} {struct lconv}
|
|
@standards{ISO, locale.h}
|
|
@code{localeconv}'s return value is of this data type. Its elements are
|
|
described in the following subsections.
|
|
@end deftp
|
|
|
|
If a member of the structure @code{struct lconv} has type @code{char},
|
|
and the value is @code{CHAR_MAX}, it means that the current locale has
|
|
no value for that parameter.
|
|
|
|
@menu
|
|
* General Numeric:: Parameters for formatting numbers and
|
|
currency amounts.
|
|
* Currency Symbol:: How to print the symbol that identifies an
|
|
amount of money (e.g. @samp{$}).
|
|
* Sign of Money Amount:: How to print the (positive or negative) sign
|
|
for a monetary amount, if one exists.
|
|
@end menu
|
|
|
|
@node General Numeric, Currency Symbol, , The Lame Way to Locale Data
|
|
@subsubsection Generic Numeric Formatting Parameters
|
|
|
|
These are the standard members of @code{struct lconv}; there may be
|
|
others.
|
|
|
|
@table @code
|
|
@item char *decimal_point
|
|
@itemx char *mon_decimal_point
|
|
These are the decimal-point separators used in formatting non-monetary
|
|
and monetary quantities, respectively. In the @samp{C} locale, the
|
|
value of @code{decimal_point} is @code{"."}, and the value of
|
|
@code{mon_decimal_point} is @code{""}.
|
|
@cindex decimal-point separator
|
|
|
|
@item char *thousands_sep
|
|
@itemx char *mon_thousands_sep
|
|
These are the separators used to delimit groups of digits to the left of
|
|
the decimal point in formatting non-monetary and monetary quantities,
|
|
respectively. In the @samp{C} locale, both members have a value of
|
|
@code{""} (the empty string).
|
|
|
|
@item char *grouping
|
|
@itemx char *mon_grouping
|
|
These are strings that specify how to group the digits to the left of
|
|
the decimal point. @code{grouping} applies to non-monetary quantities
|
|
and @code{mon_grouping} applies to monetary quantities. Use either
|
|
@code{thousands_sep} or @code{mon_thousands_sep} to separate the digit
|
|
groups.
|
|
@cindex grouping of digits
|
|
|
|
Each member of these strings is to be interpreted as an integer value of
|
|
type @code{char}. Successive numbers (from left to right) give the
|
|
sizes of successive groups (from right to left, starting at the decimal
|
|
point.) The last member is either @code{0}, in which case the previous
|
|
member is used over and over again for all the remaining groups, or
|
|
@code{CHAR_MAX}, in which case there is no more grouping---or, put
|
|
another way, any remaining digits form one large group without
|
|
separators.
|
|
|
|
For example, if @code{grouping} is @code{"\04\03\02"}, the correct
|
|
grouping for the number @code{123456787654321} is @samp{12}, @samp{34},
|
|
@samp{56}, @samp{78}, @samp{765}, @samp{4321}. This uses a group of 4
|
|
digits at the end, preceded by a group of 3 digits, preceded by groups
|
|
of 2 digits (as many as needed). With a separator of @samp{,}, the
|
|
number would be printed as @samp{12,34,56,78,765,4321}.
|
|
|
|
A value of @code{"\03"} indicates repeated groups of three digits, as
|
|
normally used in the U.S.
|
|
|
|
In the standard @samp{C} locale, both @code{grouping} and
|
|
@code{mon_grouping} have a value of @code{""}. This value specifies no
|
|
grouping at all.
|
|
|
|
@item char int_frac_digits
|
|
@itemx char frac_digits
|
|
These are small integers indicating how many fractional digits (to the
|
|
right of the decimal point) should be displayed in a monetary value in
|
|
international and local formats, respectively. (Most often, both
|
|
members have the same value.)
|
|
|
|
In the standard @samp{C} locale, both of these members have the value
|
|
@code{CHAR_MAX}, meaning ``unspecified''. The ISO standard doesn't say
|
|
what to do when you find this value; we recommend printing no
|
|
fractional digits. (This locale also specifies the empty string for
|
|
@code{mon_decimal_point}, so printing any fractional digits would be
|
|
confusing!)
|
|
@end table
|
|
|
|
@node Currency Symbol, Sign of Money Amount, General Numeric, The Lame Way to Locale Data
|
|
@subsubsection Printing the Currency Symbol
|
|
@cindex currency symbols
|
|
|
|
These members of the @code{struct lconv} structure specify how to print
|
|
the symbol to identify a monetary value---the international analog of
|
|
@samp{$} for US dollars.
|
|
|
|
Each country has two standard currency symbols. The @dfn{local currency
|
|
symbol} is used commonly within the country, while the
|
|
@dfn{international currency symbol} is used internationally to refer to
|
|
that country's currency when it is necessary to indicate the country
|
|
unambiguously.
|
|
|
|
For example, many countries use the dollar as their monetary unit, and
|
|
when dealing with international currencies it's important to specify
|
|
that one is dealing with (say) Canadian dollars instead of U.S. dollars
|
|
or Australian dollars. But when the context is known to be Canada,
|
|
there is no need to make this explicit---dollar amounts are implicitly
|
|
assumed to be in Canadian dollars.
|
|
|
|
@table @code
|
|
@item char *currency_symbol
|
|
The local currency symbol for the selected locale.
|
|
|
|
In the standard @samp{C} locale, this member has a value of @code{""}
|
|
(the empty string), meaning ``unspecified''. The ISO standard doesn't
|
|
say what to do when you find this value; we recommend you simply print
|
|
the empty string as you would print any other string pointed to by this
|
|
variable.
|
|
|
|
@item char *int_curr_symbol
|
|
The international currency symbol for the selected locale.
|
|
|
|
The value of @code{int_curr_symbol} should normally consist of a
|
|
three-letter abbreviation determined by the international standard
|
|
@cite{ISO 4217 Codes for the Representation of Currency and Funds},
|
|
followed by a one-character separator (often a space).
|
|
|
|
In the standard @samp{C} locale, this member has a value of @code{""}
|
|
(the empty string), meaning ``unspecified''. We recommend you simply print
|
|
the empty string as you would print any other string pointed to by this
|
|
variable.
|
|
|
|
@item char p_cs_precedes
|
|
@itemx char n_cs_precedes
|
|
@itemx char int_p_cs_precedes
|
|
@itemx char int_n_cs_precedes
|
|
These members are @code{1} if the @code{currency_symbol} or
|
|
@code{int_curr_symbol} strings should precede the value of a monetary
|
|
amount, or @code{0} if the strings should follow the value. The
|
|
@code{p_cs_precedes} and @code{int_p_cs_precedes} members apply to
|
|
positive amounts (or zero), and the @code{n_cs_precedes} and
|
|
@code{int_n_cs_precedes} members apply to negative amounts.
|
|
|
|
In the standard @samp{C} locale, all of these members have a value of
|
|
@code{CHAR_MAX}, meaning ``unspecified''. The ISO standard doesn't say
|
|
what to do when you find this value. We recommend printing the
|
|
currency symbol before the amount, which is right for most countries.
|
|
In other words, treat all nonzero values alike in these members.
|
|
|
|
The members with the @code{int_} prefix apply to the
|
|
@code{int_curr_symbol} while the other two apply to
|
|
@code{currency_symbol}.
|
|
|
|
@item char p_sep_by_space
|
|
@itemx char n_sep_by_space
|
|
@itemx char int_p_sep_by_space
|
|
@itemx char int_n_sep_by_space
|
|
These members are @code{1} if a space should appear between the
|
|
@code{currency_symbol} or @code{int_curr_symbol} strings and the
|
|
amount, or @code{0} if no space should appear. The
|
|
@code{p_sep_by_space} and @code{int_p_sep_by_space} members apply to
|
|
positive amounts (or zero), and the @code{n_sep_by_space} and
|
|
@code{int_n_sep_by_space} members apply to negative amounts.
|
|
|
|
In the standard @samp{C} locale, all of these members have a value of
|
|
@code{CHAR_MAX}, meaning ``unspecified''. The ISO standard doesn't say
|
|
what you should do when you find this value; we suggest you treat it as
|
|
1 (print a space). In other words, treat all nonzero values alike in
|
|
these members.
|
|
|
|
The members with the @code{int_} prefix apply to the
|
|
@code{int_curr_symbol} while the other two apply to
|
|
@code{currency_symbol}. There is one specialty with the
|
|
@code{int_curr_symbol}, though. Since all legal values contain a space
|
|
at the end of the string one either prints this space (if the currency
|
|
symbol must appear in front and must be separated) or one has to avoid
|
|
printing this character at all (especially when at the end of the
|
|
string).
|
|
@end table
|
|
|
|
@node Sign of Money Amount, , Currency Symbol, The Lame Way to Locale Data
|
|
@subsubsection Printing the Sign of a Monetary Amount
|
|
|
|
These members of the @code{struct lconv} structure specify how to print
|
|
the sign (if any) of a monetary value.
|
|
|
|
@table @code
|
|
@item char *positive_sign
|
|
@itemx char *negative_sign
|
|
These are strings used to indicate positive (or zero) and negative
|
|
monetary quantities, respectively.
|
|
|
|
In the standard @samp{C} locale, both of these members have a value of
|
|
@code{""} (the empty string), meaning ``unspecified''.
|
|
|
|
The ISO standard doesn't say what to do when you find this value; we
|
|
recommend printing @code{positive_sign} as you find it, even if it is
|
|
empty. For a negative value, print @code{negative_sign} as you find it
|
|
unless both it and @code{positive_sign} are empty, in which case print
|
|
@samp{-} instead. (Failing to indicate the sign at all seems rather
|
|
unreasonable.)
|
|
|
|
@item char p_sign_posn
|
|
@itemx char n_sign_posn
|
|
@itemx char int_p_sign_posn
|
|
@itemx char int_n_sign_posn
|
|
These members are small integers that indicate how to
|
|
position the sign for nonnegative and negative monetary quantities,
|
|
respectively. (The string used for the sign is what was specified with
|
|
@code{positive_sign} or @code{negative_sign}.) The possible values are
|
|
as follows:
|
|
|
|
@table @code
|
|
@item 0
|
|
The currency symbol and quantity should be surrounded by parentheses.
|
|
|
|
@item 1
|
|
Print the sign string before the quantity and currency symbol.
|
|
|
|
@item 2
|
|
Print the sign string after the quantity and currency symbol.
|
|
|
|
@item 3
|
|
Print the sign string right before the currency symbol.
|
|
|
|
@item 4
|
|
Print the sign string right after the currency symbol.
|
|
|
|
@item CHAR_MAX
|
|
``Unspecified''. Both members have this value in the standard
|
|
@samp{C} locale.
|
|
@end table
|
|
|
|
The ISO standard doesn't say what you should do when the value is
|
|
@code{CHAR_MAX}. We recommend you print the sign after the currency
|
|
symbol.
|
|
|
|
The members with the @code{int_} prefix apply to the
|
|
@code{int_curr_symbol} while the other two apply to
|
|
@code{currency_symbol}.
|
|
@end table
|
|
|
|
@node The Elegant and Fast Way, , The Lame Way to Locale Data, Locale Information
|
|
@subsection Pinpoint Access to Locale Data
|
|
|
|
When writing the X/Open Portability Guide the authors realized that the
|
|
@code{localeconv} function is not enough to provide reasonable access to
|
|
locale information. The information which was meant to be available
|
|
in the locale (as later specified in the POSIX.1 standard) requires more
|
|
ways to access it. Therefore the @code{nl_langinfo} function
|
|
was introduced.
|
|
|
|
@deftypefun {char *} nl_langinfo (nl_item @var{item})
|
|
@standards{XOPEN, langinfo.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@assafe{}@acsafe{}}
|
|
@c It calls _nl_langinfo_l with the current locale, which returns a
|
|
@c pointer into constant strings defined in locale data structures.
|
|
The @code{nl_langinfo} function can be used to access individual
|
|
elements of the locale categories. Unlike the @code{localeconv}
|
|
function, which returns all the information, @code{nl_langinfo}
|
|
lets the caller select what information it requires. This is very
|
|
fast and it is not a problem to call this function multiple times.
|
|
|
|
A second advantage is that in addition to the numeric and monetary
|
|
formatting information, information from the
|
|
@code{LC_TIME} and @code{LC_MESSAGES} categories is available.
|
|
|
|
@pindex langinfo.h
|
|
The type @code{nl_item} is defined in @file{nl_types.h}. The argument
|
|
@var{item} is a numeric value defined in the header @file{langinfo.h}.
|
|
The X/Open standard defines the following values:
|
|
|
|
@vtable @code
|
|
@item CODESET
|
|
@code{nl_langinfo} returns a string with the name of the coded character
|
|
set used in the selected locale.
|
|
|
|
@item ABDAY_1
|
|
@itemx ABDAY_2
|
|
@itemx ABDAY_3
|
|
@itemx ABDAY_4
|
|
@itemx ABDAY_5
|
|
@itemx ABDAY_6
|
|
@itemx ABDAY_7
|
|
@code{nl_langinfo} returns the abbreviated weekday name. @code{ABDAY_1}
|
|
corresponds to Sunday.
|
|
@item DAY_1
|
|
@itemx DAY_2
|
|
@itemx DAY_3
|
|
@itemx DAY_4
|
|
@itemx DAY_5
|
|
@itemx DAY_6
|
|
@itemx DAY_7
|
|
Similar to @code{ABDAY_1}, etc.,@: but here the return value is the
|
|
unabbreviated weekday name.
|
|
@item ABMON_1
|
|
@itemx ABMON_2
|
|
@itemx ABMON_3
|
|
@itemx ABMON_4
|
|
@itemx ABMON_5
|
|
@itemx ABMON_6
|
|
@itemx ABMON_7
|
|
@itemx ABMON_8
|
|
@itemx ABMON_9
|
|
@itemx ABMON_10
|
|
@itemx ABMON_11
|
|
@itemx ABMON_12
|
|
The return value is the abbreviated name of the month, in the
|
|
grammatical form used when the month forms part of a complete date.
|
|
@code{ABMON_1} corresponds to January.
|
|
@item MON_1
|
|
@itemx MON_2
|
|
@itemx MON_3
|
|
@itemx MON_4
|
|
@itemx MON_5
|
|
@itemx MON_6
|
|
@itemx MON_7
|
|
@itemx MON_8
|
|
@itemx MON_9
|
|
@itemx MON_10
|
|
@itemx MON_11
|
|
@itemx MON_12
|
|
Similar to @code{ABMON_1}, etc.,@: but here the month names are not
|
|
abbreviated. Here the first value @code{MON_1} also corresponds to
|
|
January.
|
|
@item ALTMON_1
|
|
@itemx ALTMON_2
|
|
@itemx ALTMON_3
|
|
@itemx ALTMON_4
|
|
@itemx ALTMON_5
|
|
@itemx ALTMON_6
|
|
@itemx ALTMON_7
|
|
@itemx ALTMON_8
|
|
@itemx ALTMON_9
|
|
@itemx ALTMON_10
|
|
@itemx ALTMON_11
|
|
@itemx ALTMON_12
|
|
Similar to @code{MON_1}, etc.,@: but here the month names are in the
|
|
grammatical form used when the month is named by itself. The
|
|
@code{strftime} functions use these month names for the conversion
|
|
specifier @code{%OB} (@pxref{Formatting Calendar Time}).
|
|
|
|
Note that not all languages need two different forms of the month names,
|
|
so the strings returned for @code{MON_@dots{}} and @code{ALTMON_@dots{}}
|
|
may or may not be the same, depending on the locale.
|
|
|
|
@strong{NB:} @code{ABALTMON_@dots{}} constants corresponding to the
|
|
@code{%Ob} conversion specifier are not currently provided, but are
|
|
expected to be in a future release. In the meantime, it is possible
|
|
to use @code{_NL_ABALTMON_@dots{}}.
|
|
@item AM_STR
|
|
@itemx PM_STR
|
|
The return values are strings which can be used in the representation of time
|
|
as an hour from 1 to 12 plus an am/pm specifier.
|
|
|
|
Note that in locales which do not use this time representation
|
|
these strings might be empty, in which case the am/pm format
|
|
cannot be used at all.
|
|
@item D_T_FMT
|
|
The return value can be used as a format string for @code{strftime} to
|
|
represent time and date in a locale-specific way.
|
|
@item D_FMT
|
|
The return value can be used as a format string for @code{strftime} to
|
|
represent a date in a locale-specific way.
|
|
@item T_FMT
|
|
The return value can be used as a format string for @code{strftime} to
|
|
represent time in a locale-specific way.
|
|
@item T_FMT_AMPM
|
|
The return value can be used as a format string for @code{strftime} to
|
|
represent time in the am/pm format.
|
|
|
|
Note that if the am/pm format does not make any sense for the
|
|
selected locale, the return value might be the same as the one for
|
|
@code{T_FMT}.
|
|
@item ERA
|
|
The return value represents the era used in the current locale.
|
|
|
|
Most locales do not define this value. An example of a locale which
|
|
does define this value is the Japanese one. In Japan, the traditional
|
|
representation of dates includes the name of the era corresponding to
|
|
the then-emperor's reign.
|
|
|
|
Normally it should not be necessary to use this value directly.
|
|
Specifying the @code{E} modifier in their format strings causes the
|
|
@code{strftime} functions to use this information. The format of the
|
|
returned string is not specified, and therefore you should not assume
|
|
knowledge of it on different systems.
|
|
@item ERA_YEAR
|
|
The return value gives the year in the relevant era of the locale.
|
|
As for @code{ERA} it should not be necessary to use this value directly.
|
|
@item ERA_D_T_FMT
|
|
This return value can be used as a format string for @code{strftime} to
|
|
represent dates and times in a locale-specific era-based way.
|
|
@item ERA_D_FMT
|
|
This return value can be used as a format string for @code{strftime} to
|
|
represent a date in a locale-specific era-based way.
|
|
@item ERA_T_FMT
|
|
This return value can be used as a format string for @code{strftime} to
|
|
represent time in a locale-specific era-based way.
|
|
@item ALT_DIGITS
|
|
The return value is a representation of up to @math{100} values used to
|
|
represent the values @math{0} to @math{99}. As for @code{ERA} this
|
|
value is not intended to be used directly, but instead indirectly
|
|
through the @code{strftime} function. When the modifier @code{O} is
|
|
used in a format which would otherwise use numerals to represent hours,
|
|
minutes, seconds, weekdays, months, or weeks, the appropriate value for
|
|
the locale is used instead.
|
|
@item INT_CURR_SYMBOL
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_curr_symbol} element of the @code{struct lconv}.
|
|
@item CURRENCY_SYMBOL
|
|
@itemx CRNCYSTR
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{currency_symbol} element of the @code{struct lconv}.
|
|
|
|
@code{CRNCYSTR} is a deprecated alias still required by Unix98.
|
|
@item MON_DECIMAL_POINT
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{mon_decimal_point} element of the @code{struct lconv}.
|
|
@item MON_THOUSANDS_SEP
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{mon_thousands_sep} element of the @code{struct lconv}.
|
|
@item MON_GROUPING
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{mon_grouping} element of the @code{struct lconv}.
|
|
@item POSITIVE_SIGN
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{positive_sign} element of the @code{struct lconv}.
|
|
@item NEGATIVE_SIGN
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{negative_sign} element of the @code{struct lconv}.
|
|
@item INT_FRAC_DIGITS
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_frac_digits} element of the @code{struct lconv}.
|
|
@item FRAC_DIGITS
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{frac_digits} element of the @code{struct lconv}.
|
|
@item P_CS_PRECEDES
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{p_cs_precedes} element of the @code{struct lconv}.
|
|
@item P_SEP_BY_SPACE
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{p_sep_by_space} element of the @code{struct lconv}.
|
|
@item N_CS_PRECEDES
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{n_cs_precedes} element of the @code{struct lconv}.
|
|
@item N_SEP_BY_SPACE
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{n_sep_by_space} element of the @code{struct lconv}.
|
|
@item P_SIGN_POSN
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{p_sign_posn} element of the @code{struct lconv}.
|
|
@item N_SIGN_POSN
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{n_sign_posn} element of the @code{struct lconv}.
|
|
|
|
@item INT_P_CS_PRECEDES
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_p_cs_precedes} element of the @code{struct lconv}.
|
|
@item INT_P_SEP_BY_SPACE
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_p_sep_by_space} element of the @code{struct lconv}.
|
|
@item INT_N_CS_PRECEDES
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_n_cs_precedes} element of the @code{struct lconv}.
|
|
@item INT_N_SEP_BY_SPACE
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_n_sep_by_space} element of the @code{struct lconv}.
|
|
@item INT_P_SIGN_POSN
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_p_sign_posn} element of the @code{struct lconv}.
|
|
@item INT_N_SIGN_POSN
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{int_n_sign_posn} element of the @code{struct lconv}.
|
|
|
|
@item DECIMAL_POINT
|
|
@itemx RADIXCHAR
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{decimal_point} element of the @code{struct lconv}.
|
|
|
|
The name @code{RADIXCHAR} is a deprecated alias still used in Unix98.
|
|
@item THOUSANDS_SEP
|
|
@itemx THOUSEP
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{thousands_sep} element of the @code{struct lconv}.
|
|
|
|
The name @code{THOUSEP} is a deprecated alias still used in Unix98.
|
|
@item GROUPING
|
|
The same as the value returned by @code{localeconv} in the
|
|
@code{grouping} element of the @code{struct lconv}.
|
|
@item YESEXPR
|
|
The return value is a regular expression which can be used with the
|
|
@code{regex} function to recognize a positive response to a yes/no
|
|
question. @Theglibc{} provides the @code{rpmatch} function for
|
|
easier handling in applications.
|
|
@item NOEXPR
|
|
The return value is a regular expression which can be used with the
|
|
@code{regex} function to recognize a negative response to a yes/no
|
|
question.
|
|
@item YESSTR
|
|
The return value is a locale-specific translation of the positive response
|
|
to a yes/no question.
|
|
|
|
Using this value is deprecated since it is a very special case of
|
|
message translation, and is better handled by the message
|
|
translation functions (@pxref{Message Translation}).
|
|
|
|
The use of this symbol is deprecated. Instead message translation
|
|
should be used.
|
|
@item NOSTR
|
|
The return value is a locale-specific translation of the negative response
|
|
to a yes/no question. What is said for @code{YESSTR} is also true here.
|
|
|
|
The use of this symbol is deprecated. Instead message translation
|
|
should be used.
|
|
@end vtable
|
|
|
|
The file @file{langinfo.h} defines a lot more symbols but none of them
|
|
are official. Using them is not portable, and the format of the
|
|
return values might change. Therefore we recommended you not use
|
|
them.
|
|
|
|
Note that the return value for any valid argument can be used
|
|
in all situations (with the possible exception of the am/pm time formatting
|
|
codes). If the user has not selected any locale for the
|
|
appropriate category, @code{nl_langinfo} returns the information from the
|
|
@code{"C"} locale. It is therefore possible to use this function as
|
|
shown in the example below.
|
|
|
|
If the argument @var{item} is not valid, a pointer to an empty string is
|
|
returned.
|
|
@end deftypefun
|
|
|
|
An example of @code{nl_langinfo} usage is a function which has to
|
|
print a given date and time in a locale-specific way. At first one
|
|
might think that, since @code{strftime} internally uses the locale
|
|
information, writing something like the following is enough:
|
|
|
|
@smallexample
|
|
size_t
|
|
i18n_time_n_data (char *s, size_t len, const struct tm *tp)
|
|
@{
|
|
return strftime (s, len, "%X %D", tp);
|
|
@}
|
|
@end smallexample
|
|
|
|
The format contains no weekday or month names and therefore is
|
|
internationally usable. Wrong! The output produced is something like
|
|
@code{"hh:mm:ss MM/DD/YY"}. This format is only recognizable in the
|
|
USA. Other countries use different formats. Therefore the function
|
|
should be rewritten like this:
|
|
|
|
@smallexample
|
|
size_t
|
|
i18n_time_n_data (char *s, size_t len, const struct tm *tp)
|
|
@{
|
|
return strftime (s, len, nl_langinfo (D_T_FMT), tp);
|
|
@}
|
|
@end smallexample
|
|
|
|
Now it uses the date and time format of the locale
|
|
selected when the program runs. If the user selects the locale
|
|
correctly there should never be a misunderstanding over the time and
|
|
date format.
|
|
|
|
@node Formatting Numbers, Yes-or-No Questions, Locale Information, Locales
|
|
@section A dedicated function to format numbers
|
|
|
|
We have seen that the structure returned by @code{localeconv} as well as
|
|
the values given to @code{nl_langinfo} allow you to retrieve the various
|
|
pieces of locale-specific information to format numbers and monetary
|
|
amounts. We have also seen that the underlying rules are quite complex.
|
|
|
|
Therefore the X/Open standards introduce a function which uses such
|
|
locale information, making it easier for the user to format
|
|
numbers according to these rules.
|
|
|
|
@deftypefun ssize_t strfmon (char *@var{s}, size_t @var{maxsize}, const char *@var{format}, @dots{})
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@ascuheap{}}@acunsafe{@acsmem{}}}
|
|
@c It (and strfmon_l) both call __vstrfmon_l_internal, which, besides
|
|
@c accessing the locale object passed to it, accesses the active
|
|
@c locale through isdigit (but to_digit assumes ASCII digits only).
|
|
@c It may call __printf_fp (@mtslocale @ascuheap @acsmem) and
|
|
@c guess_grouping (safe).
|
|
The @code{strfmon} function is similar to the @code{strftime} function
|
|
in that it takes a buffer, its size, a format string,
|
|
and values to write into the buffer as text in a form specified
|
|
by the format string. Like @code{strftime}, the function
|
|
also returns the number of bytes written into the buffer.
|
|
|
|
There are two differences: @code{strfmon} can take more than one
|
|
argument, and, of course, the format specification is different. Like
|
|
@code{strftime}, the format string consists of normal text, which is
|
|
output as is, and format specifiers, which are indicated by a @samp{%}.
|
|
Immediately after the @samp{%}, you can optionally specify various flags
|
|
and formatting information before the main formatting character, in a
|
|
similar way to @code{printf}:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Immediately following the @samp{%} there can be one or more of the
|
|
following flags:
|
|
@table @asis
|
|
@item @samp{=@var{f}}
|
|
The single byte character @var{f} is used for this field as the numeric
|
|
fill character. By default this character is a space character.
|
|
Filling with this character is only performed if a left precision
|
|
is specified. It is not just to fill to the given field width.
|
|
@item @samp{^}
|
|
The number is printed without grouping the digits according to the rules
|
|
of the current locale. By default grouping is enabled.
|
|
@item @samp{+}, @samp{(}
|
|
At most one of these flags can be used. They select which format to
|
|
represent the sign of a currency amount. By default, and if
|
|
@samp{+} is given, the locale equivalent of @math{+}/@math{-} is used. If
|
|
@samp{(} is given, negative amounts are enclosed in parentheses. The
|
|
exact format is determined by the values of the @code{LC_MONETARY}
|
|
category of the locale selected at program runtime.
|
|
@item @samp{!}
|
|
The output will not contain the currency symbol.
|
|
@item @samp{-}
|
|
The output will be formatted left-justified instead of right-justified if
|
|
it does not fill the entire field width.
|
|
@end table
|
|
@end itemize
|
|
|
|
The next part of the specification is an optional field width. If no
|
|
width is specified @math{0} is taken. During output, the function first
|
|
determines how much space is required. If it requires at least as many
|
|
characters as given by the field width, it is output using as much space
|
|
as necessary. Otherwise, it is extended to use the full width by
|
|
filling with the space character. The presence or absence of the
|
|
@samp{-} flag determines the side at which such padding occurs. If
|
|
present, the spaces are added at the right making the output
|
|
left-justified, and vice versa.
|
|
|
|
So far the format looks familiar, being similar to the @code{printf} and
|
|
@code{strftime} formats. However, the next two optional fields
|
|
introduce something new. The first one is a @samp{#} character followed
|
|
by a decimal digit string. The value of the digit string specifies the
|
|
number of @emph{digit} positions to the left of the decimal point (or
|
|
equivalent). This does @emph{not} include the grouping character when
|
|
the @samp{^} flag is not given. If the space needed to print the number
|
|
does not fill the whole width, the field is padded at the left side with
|
|
the fill character, which can be selected using the @samp{=} flag and by
|
|
default is a space. For example, if the field width is selected as 6
|
|
and the number is @math{123}, the fill character is @samp{*} the result
|
|
will be @samp{***123}.
|
|
|
|
The second optional field starts with a @samp{.} (period) and consists
|
|
of another decimal digit string. Its value describes the number of
|
|
characters printed after the decimal point. The default is selected
|
|
from the current locale (@code{frac_digits}, @code{int_frac_digits}, see
|
|
@pxref{General Numeric}). If the exact representation needs more digits
|
|
than given by the field width, the displayed value is rounded. If the
|
|
number of fractional digits is selected to be zero, no decimal point is
|
|
printed.
|
|
|
|
As a GNU extension, the @code{strfmon} implementation in @theglibc{}
|
|
allows an optional @samp{L} next as a format modifier. If this modifier
|
|
is given, the argument is expected to be a @code{long double} instead of
|
|
a @code{double} value.
|
|
|
|
Finally, the last component is a format specifier. There are three
|
|
specifiers defined:
|
|
|
|
@table @asis
|
|
@item @samp{i}
|
|
Use the locale's rules for formatting an international currency value.
|
|
@item @samp{n}
|
|
Use the locale's rules for formatting a national currency value.
|
|
@item @samp{%}
|
|
Place a @samp{%} in the output. There must be no flag, width
|
|
specifier or modifier given, only @samp{%%} is allowed.
|
|
@end table
|
|
|
|
As for @code{printf}, the function reads the format string
|
|
from left to right and uses the values passed to the function following
|
|
the format string. The values are expected to be either of type
|
|
@code{double} or @code{long double}, depending on the presence of the
|
|
modifier @samp{L}. The result is stored in the buffer pointed to by
|
|
@var{s}. At most @var{maxsize} characters are stored.
|
|
|
|
The return value of the function is the number of characters stored in
|
|
@var{s}, including the terminating @code{NULL} byte. If the number of
|
|
characters stored would exceed @var{maxsize}, the function returns
|
|
@math{-1} and the content of the buffer @var{s} is unspecified. In this
|
|
case @code{errno} is set to @code{E2BIG}.
|
|
@end deftypefun
|
|
|
|
A few examples should make clear how the function works. It is
|
|
assumed that all the following pieces of code are executed in a program
|
|
which uses the USA locale (@code{en_US}). The simplest
|
|
form of the format is this:
|
|
|
|
@smallexample
|
|
strfmon (buf, 100, "@@%n@@%n@@%n@@", 123.45, -567.89, 12345.678);
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The output produced is
|
|
@smallexample
|
|
"@@$123.45@@-$567.89@@$12,345.68@@"
|
|
@end smallexample
|
|
|
|
We can notice several things here. First, the widths of the output
|
|
numbers are different. We have not specified a width in the format
|
|
string, and so this is no wonder. Second, the third number is printed
|
|
using thousands separators. The thousands separator for the
|
|
@code{en_US} locale is a comma. The number is also rounded.
|
|
@math{.678} is rounded to @math{.68} since the format does not specify a
|
|
precision and the default value in the locale is @math{2}. Finally,
|
|
note that the national currency symbol is printed since @samp{%n} was
|
|
used, not @samp{i}. The next example shows how we can align the output.
|
|
|
|
@smallexample
|
|
strfmon (buf, 100, "@@%=*11n@@%=*11n@@%=*11n@@", 123.45, -567.89, 12345.678);
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The output this time is:
|
|
|
|
@smallexample
|
|
"@@ $123.45@@ -$567.89@@ $12,345.68@@"
|
|
@end smallexample
|
|
|
|
Two things stand out. Firstly, all fields have the same width (eleven
|
|
characters) since this is the width given in the format and since no
|
|
number required more characters to be printed. The second important
|
|
point is that the fill character is not used. This is correct since the
|
|
white space was not used to achieve a precision given by a @samp{#}
|
|
modifier, but instead to fill to the given width. The difference
|
|
becomes obvious if we now add a width specification.
|
|
|
|
@smallexample
|
|
strfmon (buf, 100, "@@%=*11#5n@@%=*11#5n@@%=*11#5n@@",
|
|
123.45, -567.89, 12345.678);
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The output is
|
|
|
|
@smallexample
|
|
"@@ $***123.45@@-$***567.89@@ $12,456.68@@"
|
|
@end smallexample
|
|
|
|
Here we can see that all the currency symbols are now aligned, and that
|
|
the space between the currency sign and the number is filled with the
|
|
selected fill character. Note that although the width is selected to be
|
|
@math{5} and @math{123.45} has three digits left of the decimal point,
|
|
the space is filled with three asterisks. This is correct since, as
|
|
explained above, the width does not include the positions used to store
|
|
thousands separators. One last example should explain the remaining
|
|
functionality.
|
|
|
|
@smallexample
|
|
strfmon (buf, 100, "@@%=0(16#5.3i@@%=0(16#5.3i@@%=0(16#5.3i@@",
|
|
123.45, -567.89, 12345.678);
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This rather complex format string produces the following output:
|
|
|
|
@smallexample
|
|
"@@ USD 000123,450 @@(USD 000567.890)@@ USD 12,345.678 @@"
|
|
@end smallexample
|
|
|
|
The most noticeable change is the alternative way of representing
|
|
negative numbers. In financial circles this is often done using
|
|
parentheses, and this is what the @samp{(} flag selected. The fill
|
|
character is now @samp{0}. Note that this @samp{0} character is not
|
|
regarded as a numeric zero, and therefore the first and second numbers
|
|
are not printed using a thousands separator. Since we used the format
|
|
specifier @samp{i} instead of @samp{n}, the international form of the
|
|
currency symbol is used. This is a four letter string, in this case
|
|
@code{"USD "}. The last point is that since the precision right of the
|
|
decimal point is selected to be three, the first and second numbers are
|
|
printed with an extra zero at the end and the third number is printed
|
|
without rounding.
|
|
|
|
@node Yes-or-No Questions, , Formatting Numbers , Locales
|
|
@section Yes-or-No Questions
|
|
|
|
Some non GUI programs ask a yes-or-no question. If the messages
|
|
(especially the questions) are translated into foreign languages, be
|
|
sure that you localize the answers too. It would be very bad habit to
|
|
ask a question in one language and request the answer in another, often
|
|
English.
|
|
|
|
@Theglibc{} contains @code{rpmatch} to give applications easy
|
|
access to the corresponding locale definitions.
|
|
|
|
@deftypefun int rpmatch (const char *@var{response})
|
|
@standards{GNU, stdlib.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @asulock{} @ascudlopen{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{} @acsfd{}}}
|
|
@c Calls nl_langinfo with YESEXPR and NOEXPR, triggering @mtslocale but
|
|
@c it's regcomp and regexec that bring in all of the safety issues.
|
|
@c regfree is also called, but it doesn't introduce any further issues.
|
|
The function @code{rpmatch} checks the string in @var{response} for whether
|
|
or not it is a correct yes-or-no answer and if yes, which one. The
|
|
check uses the @code{YESEXPR} and @code{NOEXPR} data in the
|
|
@code{LC_MESSAGES} category of the currently selected locale. The
|
|
return value is as follows:
|
|
|
|
@table @code
|
|
@item 1
|
|
The user entered an affirmative answer.
|
|
|
|
@item 0
|
|
The user entered a negative answer.
|
|
|
|
@item -1
|
|
The answer matched neither the @code{YESEXPR} nor the @code{NOEXPR}
|
|
regular expression.
|
|
@end table
|
|
|
|
This function is not standardized but available beside in @theglibc{} at
|
|
least also in the IBM AIX library.
|
|
@end deftypefun
|
|
|
|
@noindent
|
|
This function would normally be used like this:
|
|
|
|
@smallexample
|
|
@dots{}
|
|
/* @r{Use a safe default.} */
|
|
_Bool doit = false;
|
|
|
|
fputs (gettext ("Do you really want to do this? "), stdout);
|
|
fflush (stdout);
|
|
/* @r{Prepare the @code{getline} call.} */
|
|
line = NULL;
|
|
len = 0;
|
|
while (getline (&line, &len, stdin) >= 0)
|
|
@{
|
|
/* @r{Check the response.} */
|
|
int res = rpmatch (line);
|
|
if (res >= 0)
|
|
@{
|
|
/* @r{We got a definitive answer.} */
|
|
if (res > 0)
|
|
doit = true;
|
|
break;
|
|
@}
|
|
@}
|
|
/* @r{Free what @code{getline} allocated.} */
|
|
free (line);
|
|
@end smallexample
|
|
|
|
Note that the loop continues until a read error is detected or until a
|
|
definitive (positive or negative) answer is read.
|