locale.html

unix 下的C开发手册,还用详细的例程。

category defines character classification, case conversion and other
character attributes.
In addition, a series of characters can be represented by
three adjacent periods representing an ellipsis symbol (...).
The ellipsis specification is interpreted
as meaning that all values between the
values preceding and following it represent valid characters.
The ellipsis specification is valid only within
a single encoded character set;
that is, within a group of characters of the same size.
An ellipsis is
interpreted as including in the list all characters with an encoded
value higher than the encoded value of the character preceding the
ellipsis and lower than the encoded value of the character following
the ellipsis.
<p>
<b>Example</b>:
<code>
<pre>
\x30;...;\x39;
</code>
</pre>
includes in the character class all characters with encoded values
between the endpoints.
<p>
The following keywords are recognised.
In the descriptions, the term &quot;automatically included&quot;
means that it is not an error either to
include or omit any of the referenced characters;
the implementation will provide them if missing
(even if the entire keyword is missing)
and accept them silently if present.
When the implementation automatically includes
a missing character, it will have an encoded value
dependent on the charmap
file in effect (see the description of the
<i><a href="../xcu/localedef.html">localedef</a></i>
<b>-f</b>
option); otherwise, it will have a value
derived from an implementation-dependent character mapping.
<p>
The character classes
<b>digit</b>,
<b>xdigit</b>,
<b>lower</b>,
<b>upper</b>
and
<b>space</b>
have a set of automatically included characters.
These only need to
be specified if the character values (that is, encoding) differ
from the implementation default values.
It is not possible to define a locale without these
automatically included characters unless some
implementation extension is used to prevent their inclusion.
Such a definition would not be a proper superset of the
C or POSIX locale and thus, it might not be possible for
applications conforming to the XSI to work properly.
<dl compact>

<dt><b>upper</b><dd>Define characters to be classified as upper-case letters.

In the POSIX locale,
the 26 upper-case letters
are included:
<code>
<pre>
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
</code>
</pre>

In a locale definition file,
no character specified for the keywords
<b>cntrl</b>,
<b>digit</b>,
<b>punct</b>
or
<b>space</b>
can be specified.
The upper-case letters
A
to
Z,
as defined in
<xref href=charmap><a href="charset.html#tag_001_004">
Character Set Description File
</a></xref>
(the portable character set),
are automatically included in this class.


<dt><b>lower</b><dd>Define characters to be classified as lower-case letters.

In the POSIX locale,
the 26 lower-case letters
are included:
<code>
<pre>
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
</code>
</pre>

In a locale definition file,
no character specified for the keywords
<b>cntrl</b>,
<b>digit</b>,
<b>punct</b>
or
<b>space</b>
can be specified.
The lower-case letters
a
to
z
of the portable character set
are automatically included in this class.

<dt><b>alpha</b><dd>Define characters to be classified as letters.

In the POSIX locale,
all characters in the classes
<b>upper</b>
and
<b>lower</b>
are included.

In a locale definition file,
no character specified for the keywords
<b>cntrl</b>,
<b>digit</b>,
<b>punct</b>
or
<b>space</b>
can be specified.
Characters classified as either
<b>upper</b>
or
<b>lower</b>
are automatically included in this class.

<dt><b>digit</b><dd>Define the characters to be classified as numeric digits.

In the POSIX locale, only:
<code>
<pre>
0 1 2 3 4 5 6 7 8 9
</code>
</pre>
are included.

In a locale definition file,
only the digits
0,
1,
2,
3,
4,
5,
6,
7,
8
and
9
can be specified,
and in
contiguous ascending sequence by numerical value.
The digits
0
to
9
of the portable character set
are automatically included in this class.

The definition of character class
<b>digit</b>
requires that only ten
characters  the ones defining digits  can be specified;
alternative digits (for example, Hindi or Kanji) cannot be specified here.
However, the encoding may vary if an implementation supports
more than one encoding.

<dt><b>space</b><dd>Define characters to be classified as white-space characters.

In the POSIX locale, at a minimum, the characters
space, form-feed, newline, carriage-return, tab and vertical-tab
are included.

In a locale definition file,
no character specified for the keywords
<b>upper</b>,
<b>lower</b>,
<b>alpha</b>,
<b>digit</b>,
<b>graph</b>
or
<b>xdigit</b>
can be specified.
The characters space, form-feed, newline, carriage-return,
tab and vertical-tab of the portable character set,
and any characters included in the class
<b>blank</b>
are automatically included in this class.

<dt><b>cntrl</b><dd>Define characters to be classified as control characters.

In the POSIX locale,
no characters in classes
<b>alpha</b>
or
<b>print</b>
are included.

In a locale definition file,
no character specified for the keywords
<b>upper</b>,
<b>lower</b>,
<b>alpha</b>,
<b>digit</b>,
<b>punct</b>,
<b>graph</b>,
<b>print</b>
or
<b>xdigit</b>
can be specified.

<dt><b>punct</b><dd>Define characters to be classified as punctuation characters.

In the POSIX locale, neither the space
character nor any characters in classes
<b>alpha</b>,
<b>digit</b>
or
<b>cntrl</b>
are included.

In a locale definition file,
no character specified for the keywords
<b>upper</b>,
<b>lower</b>,
<b>alpha</b>,
<b>digit</b>,
<b>cntrl</b>,
<b>xdigit</b>
or as the space character can be specified.


<dt><b>graph</b><dd>Define characters to be classified as printable characters, not including the
space
character.

In the POSIX locale,
all characters in classes
<b>alpha</b>,
<b>digit</b>
and
<b>punct</b>
are included;
no characters in class
<b>cntrl</b>
are included.

In a locale definition file,
characters specified for the keywords
<b>upper</b>,
<b>lower</b>,
<b>alpha</b>,
<b>digit</b>,
<b>xdigit</b>
and
<b>punct</b>
are automatically included in this class.
No character specified for the keyword
<b>cntrl</b>
can be specified.

<dt><b>print</b><dd>Define characters to be classified as printable characters, including the
space
character.

In the POSIX locale,
all characters in class
<b>graph</b>
are included;
no characters in class
<b>cntrl</b>
are included.

In a locale definition file,
characters specified for the keywords
<b>upper</b>,
<b>lower</b>,
<b>alpha</b>,
<b>digit</b>,
<b>xdigit</b>,
<b>punct</b>
and the space character are automatically included in this class.
No character specified for the keyword
<b>cntrl</b>
can be specified.

<dt><b>xdigit</b><dd>Define the characters to be classified as hexadecimal digits.

In the POSIX locale, only:
<code>
<pre>
0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f
</code>
</pre>
are included.

In a locale definition file,
only the characters defined for the class
<b>digit</b>
can 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,
with each set in ascending order (for example
A,
B,
C,
D,
E,
F,
a,
b,
c,
d,
e,
f).
The digits
0
to
9,
the upper-case letters
A
to
F
and the lower-case letters
a
to
f
of the portable character set
are automatically included in this class.

The definition of character class
<b>xdigit</b>
requires that the characters included in character class
<b>digit</b>
be included here also.

<dt><b>blank</b><dd>Define characters to be classified as blank characters.

In the POSIX locale, only the space and tab characters are included.

In a locale definition file, the characters space and tab
are automatically included in this class.

<dt><b>charclass</b><dd>Define one or more locale-specific character class names
as strings separated by semicolons.
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 of a character class name
cannot be a digit.
The name cannot match any of the LC_CTYPE
keywords defined in this specification.

<dt><i>charclass-name</i><dd>Define characters to be classified as belonging
to the named locale-specific character class.
In the POSIX locale, the locale-specific
named character classes need not exist.

If a class name is defined by a
<b>charclass</b>
keyword, but no characters are subsequently
assigned to it, this is not an error;
it represents a class without any characters belonging to it.

The
<i>charclass-name</i>
can be used as the
<i>property</i>
argument to the
<i><a href="../xsh/wctype.html">wctype()</a></i>
function, in regular expression and shell pattern-matching
bracket expressions, and by the
<i><a href="../xcu/tr.html">tr</a></i>
command.

<dt><b>toupper</b><dd>Define the mapping of lower-case letters to upper-case letters.

In the POSIX locale,
at a minimum, the 26 lower-case characters:
<code>
<pre>
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
</code>
</pre>
are mapped to the corresponding 26 upper-case characters:
<code>
<pre>
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
</code>
</pre>

In a locale definition file,
the operand consists of character pairs, separated by semicolons.
The characters in each character pair are separated by a comma and
the pair enclosed by parentheses.
The first character in each pair is the lower-case letter, the
second the corresponding upper-case letter.
Only characters specified for the keywords
<b>lower</b>
and
<b>upper</b>
can be specified.