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"%OB" is considered a conversion specifier ("B" is the format
specifier), and the list of format specifiers for months in the
description of the optional "O" modifier was incomplete. A
cross-reference from the ALTMON_* constants to the strftime section
is also provided. Lastly, some grammatical fixes (commas) are made
and paragraphs refactored (rewrapped).
* manual/locale.texi (ALTMON_1, ALTMON_2, ALTMON_3, ALTMON_4,
ALTMON_5, ALTMON_6, ALTMON_7, ALTMON_8, ALTMON_9, ALTMON_10,
ALTMON_11, ALTMON_12): Improve documentation.
* manual/time.texi (strftime): Likewise.
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
|
|
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
|
|
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
|
|
@c ought to be MT-Safe, so we're ruling out the use of this function
|
|
@c once threads are started. It takes a write lock itself, but it may
|
|
@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
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|
@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)
|
|
@c isdigit_l ok (C locale)
|
|
@c malloc @ascuheap @acsmem
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|
@c tolower_l ok (C locale)
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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 __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
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|
@c realloc @ascuheap @acsmem
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@c realloc @ascuheap @acsmem
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@c fclose @ascuheap @asulock @acsmem @acsfd @aculock
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@c qsort @ascuheap @acsmem
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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
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@c malloc @ascuheap @acsmem
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@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
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|
@c malloc @ascuheap @acsmem
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|
@c strtok_r ok
|
|
@c libc_lock_unlock @aculock
|
|
@c read_conf_file @ascuheap @asucorrupt @asulock @acsmem @acucorrupt @acsfd @aculock
|
|
@c fopen @ascuheap @asulock @acsmem @acsfd @aculock
|
|
@c fsetlocking ok
|
|
@c feof_unlocked ok
|
|
@c getdelim @ascuheap @asucorrupt @acsmem @acucorrupt
|
|
@c isspace_l ok (C locale)
|
|
@c add_alias
|
|
@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
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|
@c add_alias2 @ascuheap @acucorrupt @acsmem
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|
@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, which, besides accessing the
|
|
@c locale object passed to it, accesses the active locale through
|
|
@c isdigit (but to_digit assumes ASCII digits only). It may call
|
|
@c __printf_fp (@mtslocale @ascuheap @acsmem) and 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.
|