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LOCALE(7)                                                               Linux Programmer's Manual                                                              LOCALE(7)

NAME
       locale - description of multilanguage support

SYNOPSIS
       #include <locale.h>

DESCRIPTION
       A locale is a set of language and cultural rules.  These cover aspects such as language for messages, different character sets, lexicographic conventions, and so
       on.  A program needs to be able to determine its locale and act accordingly to be portable to different cultures.

       The header <locale.h> declares data types, functions, and macros which are useful in this task.

       The functions it declares are setlocale(3) to set the current locale, and localeconv(3) to get information about number formatting.

       There are different categories for locale information a program might need; they are declared as macros.  Using them as the first argument  to  the  setlocale(3)
       function, it is possible to set one of these to the desired locale:

       LC_ADDRESS (GNU extension, since glibc 2.2)
              Change  settings  that  describe the formats (e.g., postal addresses) used to describe locations and geography-related items.  Applications that need this
              information can use nl_langinfo(3) to retrieve nonstandard elements, such as _NL_ADDRESS_COUNTRY_NAME (country name, in the language of  the  locale)  and
              _NL_ADDRESS_LANG_NAME  (language  name,  in the language of the locale), which return strings such as "Deutschland" and "Deutsch" (for German-language lo‐
              cales).  (Other element names are listed in <langinfo.h>.)

       LC_COLLATE
              This category governs the collation rules used for sorting and regular expressions, including character equivalence classes and  multicharacter  collating
              elements.   This locale category changes the behavior of the functions strcoll(3) and strxfrm(3), which are used to compare strings in the local alphabet.
              For example, the German sharp s is sorted as "ss".

       LC_CTYPE
              This category determines the interpretation of byte sequences as characters (e.g., single versus multibyte characters), character  classifications  (e.g.,
              alphabetic  or  digit),  and  the  behavior of character classes.  On glibc systems, this category also determines the character transliteration rules for
              iconv(1) and iconv(3).  It changes the behavior of the character handling and classification functions, such as isupper(3) and toupper(3), and the  multi‐
              byte character functions such as mblen(3) or wctomb(3).

       LC_IDENTIFICATION (GNU extension, since glibc 2.2)
              Change  settings  that relate to the metadata for the locale.  Applications that need this information can use nl_langinfo(3) to retrieve nonstandard ele‐
              ments, such as _NL_IDENTIFICATION_TITLE (title of this locale document) and _NL_IDENTIFICATION_TERRITORY (geographical territory to which this locale doc‐
              ument applies), which might return strings such as "English locale for the USA" and "USA".  (Other element names are listed in <langinfo.h>.)

       LC_MONETARY
              This category determines the formatting used for monetary-related numeric values.  This changes the information returned by localeconv(3), which describes
              the way numbers are usually printed, with details such as decimal point versus decimal comma.  This information is internally used by the  function  strf‐
              mon(3).

       LC_MESSAGES
              This  category affects the language in which messages are displayed and what an affirmative or negative answer looks like.  The GNU C library contains the
              gettext(3), ngettext(3), and rpmatch(3) functions to ease the use of this information.  The GNU gettext family of  functions  also  obey  the  environment
              variable  LANGUAGE (containing a colon-separated list of locales) if the category is set to a valid locale other than "C".  This category also affects the
              behavior of catopen(3).

       LC_MEASUREMENT (GNU extension, since glibc 2.2)
              Change the settings relating to the measurement system in the locale (i.e., metric versus US customary units).  Applications can use nl_langinfo(3) to re‐
              trieve  the  nonstandard  _NL_MEASUREMENT_MEASUREMENT  element,  which  returns  a pointer to a character that has the value 1 (metric) or 2 (US customary
              units).

       LC_NAME (GNU extension, since glibc 2.2)
              Change settings that describe the formats used to address persons.  Applications that need this information can use nl_langinfo(3) to retrieve nonstandard
              elements, such as _NL_NAME_NAME_MR (general salutation for men) and _NL_NAME_NAME_MS (general salutation for women) elements, which return strings such as
              "Herr" and "Frau" (for German-language locales).  (Other element names are listed in <langinfo.h>.)

       LC_NUMERIC
              This category determines the formatting rules used for nonmonetary numeric values—for example, the thousands separator and the radix character  (a  period
              in  most  English-speaking countries, but a comma in many other regions).  It affects functions such as printf(3), scanf(3), and strtod(3).  This informa‐
              tion can also be read with the localeconv(3) function.

       LC_PAPER (GNU extension, since glibc 2.2)
              Change the settings relating to the dimensions of the standard paper size (e.g., US letter versus A4).  Applications that need the dimensions  can  obtain
              them  by using nl_langinfo(3) to retrieve the nonstandard _NL_PAPER_WIDTH and _NL_PAPER_HEIGHT elements, which return int values specifying the dimensions
              in millimeters.

       LC_TELEPHONE (GNU extension, since glibc 2.2)
              Change settings that describe the formats to be used with telephone services.  Applications that need this information can use nl_langinfo(3) to  retrieve
              nonstandard  elements,  such  as  _NL_TELEPHONE_INT_PREFIX (international prefix used to call numbers in this locale), which returns a string such as "49"
              (for Germany).  (Other element names are listed in <langinfo.h>.)

       LC_TIME
              This category governs the formatting used for date and time values.  For example, most of Europe uses a 24-hour clock versus the 12-hour clock used in the
              United States.  The setting of this category affects the behavior of functions such as strftime(3) and strptime(3).

       LC_ALL All of the above.

       If the second argument to setlocale(3) is an empty string, "", for the default locale, it is determined using the following steps:

       1. If there is a non-null environment variable LC_ALL, the value of LC_ALL is used.

       2. If an environment variable with the same name as one of the categories above exists and is non-null, its value is used for that category.

       3. If there is a non-null environment variable LANG, the value of LANG is used.

       Values about local numeric formatting is made available in a struct lconv returned by the localeconv(3) function, which has the following declaration:

           struct lconv {

               /* Numeric (nonmonetary) information */

               char *decimal_point;     /* Radix character */
               char *thousands_sep;     /* Separator for digit groups to left
                                           of radix character */
               char *grouping;     /* Each element is the number of digits in
                                      a group; elements with higher indices
                                      are further left.  An element with value
                                      CHAR_MAX means that no further grouping
                                      is done.  An element with value 0 means
                                      that the previous element is used for
                                      all groups further left. */

               /* Remaining fields are for monetary information */

               char *int_curr_symbol;   /* First three chars are a currency
                                           symbol from ISO 4217.  Fourth char
                                           is the separator.  Fifth char
                                           is '\0'. */
               char *currency_symbol;   /* Local currency symbol */
               char *mon_decimal_point; /* Radix character */
               char *mon_thousands_sep; /* Like thousands_sep above */
               char *mon_grouping;      /* Like grouping above */
               char *positive_sign;     /* Sign for positive values */
               char *negative_sign;     /* Sign for negative values */
               char  int_frac_digits;   /* International fractional digits */
               char  frac_digits;       /* Local fractional digits */
               char  p_cs_precedes;     /* 1 if currency_symbol precedes a
                                           positive value, 0 if succeeds */
               char  p_sep_by_space;    /* 1 if a space separates
                                           currency_symbol from a positive
                                           value */
               char  n_cs_precedes;     /* 1 if currency_symbol precedes a
                                           negative value, 0 if succeeds */
               char  n_sep_by_space;    /* 1 if a space separates
                                           currency_symbol from a negative
                                           value */
               /* Positive and negative sign positions:
                  0 Parentheses surround the quantity and currency_symbol.
                  1 The sign string precedes the quantity and currency_symbol.
                  2 The sign string succeeds the quantity and currency_symbol.
                  3 The sign string immediately precedes the currency_symbol.
                  4 The sign string immediately succeeds the currency_symbol. */
               char  p_sign_posn;
               char  n_sign_posn;
           };

   POSIX.1-2008 extensions to the locale API
       POSIX.1-2008  standardized a number of extensions to the locale API, based on implementations that first appeared in version 2.3 of the GNU C library.  These ex‐
       tensions are designed to address the problem that the traditional locale APIs do not mix well with multithreaded applications and  with  applications  that  must
       deal with multiple locales.

       The extensions take the form of new functions for creating and manipulating locale objects (newlocale(3), freelocale(3), duplocale(3), and uselocale(3)) and var‐
       ious new library functions with the suffix "_l" (e.g., toupper_l(3)) that extend the traditional locale-dependent APIs (e.g., toupper(3)) to allow the specifica‐
       tion of a locale object that should apply when executing the function.

ENVIRONMENT
       The following environment variable is used by newlocale(3) and setlocale(3), and thus affects all unprivileged localized programs:

       LOCPATH
              A  list  of  pathnames,  separated by colons (':'), that should be used to find locale data.  If this variable is set, only the individual compiled locale
              data files from LOCPATH and the system default locale data path are used; any available locale archives are not used (see localedef(1)).   The  individual
              compiled  locale  data files are searched for under subdirectories which depend on the currently used locale.  For example, when en_GB.UTF-8 is used for a
              category, the following subdirectories are searched for, in this order: en_GB.UTF-8, en_GB.utf8, en_GB, en.UTF-8, en.utf8, and en.

FILES
       /usr/lib/locale/locale-archive
              Usual default locale archive location.

       /usr/lib/locale
              Usual default path for compiled individual locale files.

CONFORMING TO
       POSIX.1-2001.

SEE ALSO
       iconv(1), locale(1), localedef(1), catopen(3), gettext(3), iconv(3), localeconv(3), mbstowcs(3), newlocale(3), ngettext(3),  nl_langinfo(3),  rpmatch(3),  setlo‐
       cale(3), strcoll(3), strfmon(3), strftime(3), strxfrm(3), uselocale(3), wcstombs(3), locale(5), charsets(7), unicode(7), utf-8(7)

Linux                                                                          2021-03-22                                                                      LOCALE(7)