locale [-a|-m] locale [-ck] name...
When locale is invoked without any arguments, it shall summarize the current locale environment for each locale category as determined by the settings of the environment variables defined in the Base Definitions volume of POSIX.1-2017, Chapter 7, Locale.
When invoked with operands, it shall write values that have been assigned to the keywords in the locale categories, as follows:
The following options shall be supported:
The application shall ensure that the LANG, LC_*, and NLSPATH environment variables specify the current locale environment to be written out; they shall be used if the -a option is not specified.
"LANG=%s\n", <value>
If LANG is not set or is an empty string, the value is the empty string.
If locale is invoked without any options or operands, the names and values of the LC_* environment variables described in this volume of POSIX.1-2017 shall be written to the standard output, one variable per line, and each line using the following format. Only those variables set in the environment and not overridden by LC_ALL shall be written using this format:
"%s=%s\n", <variable_name>, <value>
The names of those LC_* variables associated with locale categories defined in this volume of POSIX.1-2017 that are not set in the environment or are overridden by LC_ALL shall be written in the following format:
"%s=\"%s\"\n", <variable_name>, <implied value>
The <implied value> shall be the name of the locale that has been selected for that category by the implementation, based on the values in LANG and LC_ALL, as described in the Base Definitions volume of POSIX.1-2017, Chapter 8, Environment Variables.
The <value> and <implied value> shown above shall be properly quoted for possible later reentry to the shell. The <value> shall not be quoted using double-quotes (so that it can be distinguished by the user from the <implied value> case, which always requires double-quotes).
The LC_ALL variable shall be written last, using the first format shown above. If it is not set, it shall be written as:
"LC_ALL=\n"
If any arguments are specified:
"%s\n", <locale name>
"%s\n", <category name>
If keywords are also selected for writing (see following items), the category name output shall precede the keyword output for that category.
If the -c option is not specified, the names of the categories shall not be written; only the keywords, as selected by the <name> operand, shall be written.
"%s=\"%s\"\n", <keyword name>, <keyword value>
If a value is a non-numeric compound keyword value, it shall either be written in the format:
"%s=\"%s\"\n", <keyword name>, <keyword value>
where the <keyword value> is a single string of values separated by <semicolon> characters, or it shall be written in the format:
"%s=%s\n", <keyword name>, <keyword value>
where the <keyword value> is encoded as a set of strings, each enclosed in double-quotation-marks, separated by <semicolon> characters.
If the keyword was charmap, the name of the charmap (if any) that was specified via the localedef -f option when the locale was created shall be written, with the word charmap as <keyword name>.
If a value is numeric, it shall be written in one of the following formats:
"%s=%d\n", <keyword name>, <keyword value> "%s=%c%o\n", <keyword name>, <escape character>, <keyword value> "%s=%cx%x\n", <keyword name>, <escape character>, <keyword value>
where the <escape character> is that identified by the escape_char keyword in the current locale; see the Base Definitions volume of POSIX.1-2017, Section 7.3, Locale Definition.
Compound keyword values (list entries) shall be separated in the output by <semicolon> characters. When included in keyword values, the <semicolon>, <backslash>, double-quote, and any control character shall be preceded (escaped) with the escape character.
"%s\n", <keyword value>
If the keyword was charmap, the name of the charmap (if any) that was specified via the localedef -f option when the locale was created shall be written.
"%s\n", <charmap>
where <charmap> is in a format suitable for use as the option-argument to the localedef -f option.
The following sections are informative.
Implementations are not required to write out the actual values for keywords in the categories LC_CTYPE and LC_COLLATE; however, they must write out the categories (allowing an application to determine, for example, which character classes are available).
LANG=locale_x LC_COLLATE=locale_y
The command locale would result in the following output:
LANG=locale_x LC_CTYPE="locale_x" LC_COLLATE=locale_y LC_TIME="locale_x" LC_NUMERIC="locale_x" LC_MONETARY="locale_x" LC_MESSAGES="locale_x" LC_ALL=
The order of presentation of the categories is not specified by this volume of POSIX.1-2017.
The command:
LC_ALL=POSIX locale -ck decimal_point
would produce:
LC_NUMERIC decimal_point="."
The following command shows an application of locale to determine whether a user-supplied response is affirmative:
printf 'Prompt for response: '
read response
if printf "%s\n$response" | grep -- -Eq "$(locale yesexpr)"
then
affirmative processing goes here
else
non-affirmative processing goes here
fi
The -m option was included to allow applications to query for the existence of charmaps. The output is a list of the charmaps (implementation-supplied and user-supplied, if any) on the system.
The -c option was included for readability when more than one category is selected (for example, via more than one keyword name or via a category name). It is valid both with and without the -k option.
The charmap keyword, which returns the name of the charmap (if any) that was used when the current locale was created, was included to allow applications needing the information to retrieve it.
According to the Base Definitions volume of POSIX.1-2017, Section 6.1, Portable Character Set, the standard requires that all supported locales must have the same encoding for <period> and <slash>, because these two characters are used within the locale-independent pathname resolution sequence. Therefore, it would be an error if locale -a listed both ASCII and EBCDIC-based locales, since those two encodings do not share the same representation for either <period> or <slash>. Any system that supports both environments would be expected to provide two POSIX locales, one in either codeset, where only the locales appropriate to the current environment can be visible at a time. In an XSI-compliant implementation, the dd utility is the only portable means for performing conversions between the two character sets.
The Base Definitions volume of POSIX.1-2017, Section 6.1, Portable Character Set, Chapter 7, Locale, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines
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