Defines the rules and symbols used to format non-monetary numeric information, is available through localeconv() . Some of the information is available in an alternative form via nl_langinfo().

These item names are the keywords recognized by the localedef utility when defining a locale. They are similar to the member names of the lconv structure defined in locale.h; localeconv() returns {CHAR_MAX} for unspecified integer items and the empty string ( "" ) for unspecified or size zero string items.

In a locale definition file, the operands are strings, formatted as indicated by the grammar in Locale Definition Grammar. For some keywords, the strings can only contain integers. Keywords that are not provided, string values set to the empty string ( "" ), or integer keywords set to -1, shall be used to indicate that the value is not available in the locale.

copy existing-locale name of an existing locale which shall be used as the definition of this category. If this keyword is specified, no other keyword shall be specified. This is a localedef utility keyword, unavailable through localeconv().
decimal_point symbol Usually a period or a comma. symbol used as the decimal delimiter (radix character) in numeric, non-monetary formatted quantities. Required.
thousands_sep symbol symbol used as a separator for groups of digits to the left of the decimal delimiter in numeric, non-monetary formatted monetary quantities.
grouping n1 [; … Size of each group of digits in formatted non-monetary quantities frequently 3. The operand is a sequence of integers separated by semicolon, specifing the number of digits in each group, with the initial integer defining the size of the group immediately preceding the decimal delimiter, and the following integers defining the preceding groups.
If the last integer is -1, then no further grouping shall be performed.
If the last integer is not -1, then the size of the previous group is repeatedly used for the remainder of the digits.
LC_NUMERIC Category in the POSIX Locale

The non-monetary numeric formatting definitions for the POSIX locale follow; the code listing depicting the localedef input, the table representing the same information with the addition of localeconv() values, and nl_langinfo() constants.

# This is the POSIX locale definition for the LC_NUMERIC category.
decimal_point    ""
thousands_sep    ""
grouping         -1