from: /pubs.opengroup.org/onlinepubs/9699919799/

copy
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.

In the locale definition file

upper
uppercase letters. POSIX: 26 uppercase letters : A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
no character specified for the keywords cntrl, digit, punct, or space shall be specified. The uppercase letters <A> to <Z>, as defined in Character Set Description File (the portable character set), are in this class.
lower
lowercase letters. POSIX: 26 lowercase letters : a b c d e f g h i j k l m n o p q r s t u v w x y z
no character specified for the keywords cntrl, digit, punct, or space shall be specified. The lowercase letters <a> to <z> of the portable character set are in this class.
alpha
letters. POSIX: upper and lower .
no character specified for the keywords cntrl, digit, punct, or space shall be specified. Characters classified as either upper or lower are in this class.
digit
Define the numeric digits. POSIX: 0 1 2 3 4 5 6 7 8 9 only the digits <zero>, <one>, <two>, <three>, <four>, <five>, <six>, <seven>, <eight>, and <nine> shall be specified, and in contiguous ascending sequence by numerical value. The digits <zero> to <nine> of the portable character set are in this class.
alnum
letters and numeric digits. Only alpha and digit shall be specified as they are in this class.
space
white-space characters. POSIX: exactly <space>, <form-feed>, <newline>, <carriage-return>, <tab>, and <vertical-tab> upper, lower, alpha, digit, graph, or xdigit shall not be specified. The <space>, <form-feed>, <newline>, <carriage-return>, <tab>, and <vertical-tab> of the portable character set, and any characters in the class blank are in this class.
cntrl
control characters. POSIX: alpha or print code>upper, lower, alpha, digit, punct, graph, print, or xdigit shall not be specified.
punct
punctuation characters. POSIX: neither the <space> nor alpha, digit, upper, lower, alpha, digit, cntrl, xdigit, or as the <space> shall not be specified.
graph
printable characters, not including the <space>. POSIX: alpha, digit, and punct upper, lower, alpha, digit, xdigit, and punct are in this class. No cntrl shall be specified.
print
printable characters, including the <space>. POSIX: characters graph upper, lower, alpha, digit, xdigit, punct, graph, and the <space> are in this class. No cntrl shall be specified.
xdigit Define the hexadecimal digits. POSIX: 0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f Only digits shall be specified, in contiguous ascending sequence by numerical value, followed by one or more sets of six characters representing the hexadecimal digits 10 to 15 inclusive. Each set in ascending order (for example, <A>, <B>, <C>, <D>, <E>, <F>, <a>, <b>, <c>, <d>, <e>, <f>). The digits <zero> to <nine>, the uppercase letters <A> to <F>, and the lowercase letters <a> to <f> of the portable character set are in this class.
blank <blank> characters. POSIX: <space> and <tab> the <space> and <tab> are in this class.

charclass
Define one or more locale-specific character class names as strings separated by <semicolon> .
Each named character class can then be defined subsequently in the LC_CTYPE definition.
A character class name consists of at least one and at most {CHARCLASS_NAME_MAX} bytes of alphanumeric characters from the portable filename character set.
The first character not be a digit.
The name not match any of the LC_CTYPE keywords
charclass-name
belonging to the named locale-specific character class. POSIX: locale-specific named character classes need not exist. If a class name is defined by charclass , but no characters are subsequently assigned to it, this is not an error; it represents a class without any characters belonging to it. The charclass-name can be used as the property argument to wctype() , in regular expression and shell pattern-matching bracket expressions, and by the tr command.
toupper
Define the mapping of lowercase letters to uppercase letters.
POSIX: at a minimum, the 26 lowercase characters:
```
a b c d e f g h i j k l m n o p q r s t u v w x y z
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
```
the operand shall consist of character pairs, separated by <semicolon> . The characters in each character pair shall be separated by a <comma> and the pair enclosed by parentheses. The first character in each pair is the lowercase letter, the second the corresponding uppercase letter. Only characters specified for the keywords lower and upper shall be specified. The lowercase letters <a> to <z>, and their corresponding uppercase letters <A> to <Z>, of the portable character set are in this mapping, but only when toupper is omitted from the locale definition.
tolower
Define the mapping of uppercase letters to lowercase letters.
POSIX: at a minimum, the 26 uppercase characters:
```
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
a b c d e f g h i j k l m n o p q r s t u v w x y z
```
the operand shall consist of character pairs, separated by <semicolon> characters. The characters in each character pair shall be separated by a <comma> and the pair enclosed by parentheses. The first character in each pair is the uppercase letter, the second the corresponding lowercase letter. Only characters specified for the keywords lower and upper shall be specified. If tolower is omitted from the locale definition, the mapping is the reverse mapping of the one specified for toupper.