nl_langinfo, nl_langinfo_l - query language and locale information

#include <langinfo.h>
char *nl_langinfo(nl_item item);
char *nl_langinfo_l(nl_item item, locale_t locale);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

    Since glibc 2.24:
        _POSIX_C_SOURCE >= 200809L
    glibc 2.23 and earlier:
        _POSIX_C_SOURCE >= 200112L

The nl_langinfo() and nl_langinfo_l() functions provide access to locale information in a more flexible way than localeconv(3). nl_langinfo() returns a string which is the value corresponding to item in the program's current global locale. nl_langinfo_l() returns a string which is the value corresponding to item for the locale identified by the locale object locale, which was previously created by newlocale(3). Individual and additional elements of the locale categories can be queried. setlocale(3) needs to be executed with proper arguments before.

Examples for the locale elements that can be specified in item using the constants defined in <langinfo.h> are:

CODESET (LC_CTYPE)

Return a string with the name of the character encoding used in the selected locale, such as "UTF-8", "ISO-8859-1", or "ANSI_X3.4-1968" (better known as US-ASCII). This is the same string that you get with "locale charmap". For a list of character encoding names, try "locale -m" (see locale(1)).

D_T_FMT (LC_TIME)

Return a string that can be used as a format string for strftime(3) to represent time and date in a locale-specific way (%c conversion specification).

D_FMT (LC_TIME)

Return a string that can be used as a format string for strftime(3) to represent a date in a locale-specific way (%x conversion specification).

T_FMT (LC_TIME)

Return a string that can be used as a format string for strftime(3) to represent a time in a locale-specific way (%X conversion specification).

AM_STR (LC_TIME)

Return a string that represents affix for ante meridiem (before noon, "AM") time. (Used in %p strftime(3) conversion specification.)

PM_STR (LC_TIME)

Return a string that represents affix for post meridiem (before midnight, "PM") time. (Used in %p strftime(3) conversion specification.)

T_FMT_AMPM (LC_TIME)

Return a string that can be used as a format string for strftime(3) to represent a time in a.m. or p.m. notation in a locale-specific way (%r conversion specification).

ERA (LC_TIME)

Return era description, which contains information about how years are counted and displayed for each era in a locale. Each era description segment shall have the format:

direction:offset:start_date:end_date:era_name:era_format

according to the definitions below:

direction

Either a "+" or a "-" character. The "+" means that years increase from the start_date towards the end_date, "-" means the opposite.

offset

The epoch year of the start_date.

start_date

A date in the form yyyy/mm/dd, where yyyy, mm, and dd are the year, month, and day numbers respectively of the start of the era.

end_date

The ending date of the era, in the same format as the start_date, or one of the two special values "-*" (minus infinity) or "+*" (plus infinity).

era_name

The name of the era, corresponding to the %EC strftime(3) conversion specification.

era_format

The format of the year in the era, corresponding to the %EY strftime(3) conversion specification.

Era description segments are separated by semicolons. Most locales do not define this value. Examples of locales that do define this value are the Japanese and Thai locales.

ERA_D_T_FMT (LC_TIME)

Return a string that can be used as a format string for strftime(3) for alternative representation of time and date in a locale-specific way (%Ec conversion specification).

ERA_D_FMT (LC_TIME)

Return a string that can be used as a format string for strftime(3) for alternative representation of a date in a locale-specific way (%Ex conversion specification).

ERA_T_FMT (LC_TIME)

Return a string that can be used as a format string for strftime(3) for alternative representation of a time in a locale-specific way (%EX conversion specification).

DAY_{1–7} (LC_TIME)

Return name of the n-th day of the week. [Warning: this follows the US convention DAY_1 = Sunday, not the international convention (ISO 8601) that Monday is the first day of the week.] (Used in %A strftime(3) conversion specification.)

ABDAY_{1–7} (LC_TIME)

Return abbreviated name of the n-th day of the week. (Used in %a strftime(3) conversion specification.)

MON_{1–12} (LC_TIME)

Return name of the n-th month. (Used in %B strftime(3) conversion specification.)

ABMON_{1–12} (LC_TIME)

Return abbreviated name of the n-th month. (Used in %b strftime(3) conversion specification.)

RADIXCHAR (LC_NUMERIC)

Return radix character (decimal dot, decimal comma, etc.).

THOUSEP (LC_NUMERIC)

Return separator character for thousands (groups of three digits).

YESEXPR (LC_MESSAGES)

Return a regular expression that can be used with the regex(3) function to recognize a positive response to a yes/no question.

NOEXPR (LC_MESSAGES)

Return a regular expression that can be used with the regex(3) function to recognize a negative response to a yes/no question.

CRNCYSTR (LC_MONETARY)

Return the currency symbol, preceded by "-" if the symbol should appear before the value, "+" if the symbol should appear after the value, or "." if the symbol should replace the radix character.

The above list covers just some examples of items that can be requested. For a more detailed list, consult The GNU C Library Reference Manual.

On success, these functions return a pointer to a string which is the value corresponding to item in the specified locale.

If no locale has been selected by setlocale(3) for the appropriate category, nl_langinfo() return a pointer to the corresponding string in the "C" locale. The same is true of nl_langinfo_l() if locale specifies a locale where langinfo data is not defined.

If item is not valid, a pointer to an empty string is returned.

The pointer returned by these functions may point to static data that may be overwritten, or the pointer itself may be invalidated, by a subsequent call to nl_langinfo(), nl_langinfo_l(), or setlocale(3). The same statements apply to nl_langinfo_l() if the locale object referred to by locale is freed or modified by freelocale(3) or newlocale(3).

POSIX specifies that the application may not modify the string returned by these functions.

The following program sets the character type and the numeric locale according to the environment and queries the terminal character set and the radix character.

#include <langinfo.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
int
main(void)
{
    setlocale(LC_CTYPE, "");
    setlocale(LC_NUMERIC, "");
    printf("%s\n", nl_langinfo(CODESET));
    printf("%s\n", nl_langinfo(RADIXCHAR));
    exit(EXIT_SUCCESS);
}

locale(1), localeconv(3), setlocale(3), charsets(7), locale(7)

The GNU C Library Reference Manual