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charnames(3pm)                        Perl Programmers Reference Guide                        charnames(3pm)



NAME
       charnames - access to Unicode character names and named character sequences; also define character
       names

SYNOPSIS
        use charnames ':full';
        print "\N{GREEK SMALL LETTER SIGMA} is called sigma.\n";
        print "\N{LATIN CAPITAL LETTER E WITH VERTICAL LINE BELOW}",
              " is an officially named sequence of two Unicode characters\n";

        use charnames ':loose';
        print "\N{Greek small-letter  sigma}",
               "can be used to ignore case, underscores, most blanks,"
               "and when you aren't sure if the official name has hyphens\n";

        use charnames ':short';
        print "\N{greek:Sigma} is an upper-case sigma.\n";

        use charnames qw(cyrillic greek);
        print "\N{sigma} is Greek sigma, and \N{be} is Cyrillic b.\n";

        use charnames ":full", ":alias" => {
          e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
          mychar => 0xE8000,  # Private use area
        };
        print "\N{e_ACUTE} is a small letter e with an acute.\n";
        print "\N{mychar} allows me to name private use characters.\n";

        use charnames ();
        print charnames::viacode(0x1234); # prints "ETHIOPIC SYLLABLE SEE"
        printf "%04X", charnames::vianame("GOTHIC LETTER AHSA"); # prints
                                                                 # "10330"
        print charnames::vianame("LATIN CAPITAL LETTER A"); # prints 65 on
                                                            # ASCII platforms;
                                                            # 193 on EBCDIC
        print charnames::string_vianame("LATIN CAPITAL LETTER A"); # prints "A"

DESCRIPTION
       Pragma "use charnames" is used to gain access to the names of the Unicode characters and named
       character sequences, and to allow you to define your own character and character sequence names.

       All forms of the pragma enable use of the following 3 functions:

       •   "charnames::string_vianame(name)" for run-time lookup of a either a character name or a named
           character sequence, returning its string representation

       •   "charnames::vianame(name)" for run-time lookup of a character name (but not a named character
           sequence) to get its ordinal value (code point)

       •   "charnames::viacode(code)" for run-time lookup of a code point to get its Unicode name.

       Starting in Perl v5.16, any occurrence of "\N{CHARNAME}" sequences in a double-quotish string
       automatically loads this module with arguments ":full" and ":short" (described below) if it hasn't
       already been loaded with different arguments, in order to compile the named Unicode character into
       position in the string.  Prior to v5.16, an explicit "use charnames" was required to enable this
       usage.  (However, prior to v5.16, the form "use charnames ();" did not enable "\N{CHARNAME}".)

       Note that "\N{U+...}", where the ... is a hexadecimal number, also inserts a character into a string.
       The character it inserts is the one whose code point (ordinal value) is equal to the number.  For
       example, "\N{U+263a}" is the Unicode (white background, black foreground) smiley face equivalent to
       "\N{WHITE SMILING FACE}".  Also note, "\N{...}" can mean a regex quantifier instead of a character
       name, when the ... is a number (or comma separated pair of numbers (see "QUANTIFIERS" in perlreref),
       and is not related to this pragma.

       The "charnames" pragma supports arguments ":full", ":loose", ":short", script names and customized
       aliases.

       If ":full" is present, for expansion of "\N{CHARNAME}", the string CHARNAME is first looked up in the
       list of standard Unicode character names.

       ":loose" is a variant of ":full" which allows CHARNAME to be less precisely specified.  Details are
       in "LOOSE MATCHES".

       If ":short" is present, and CHARNAME has the form "SCRIPT:CNAME", then CNAME is looked up as a letter
       in script SCRIPT, as described in the next paragraph.  Or, if "use charnames" is used with script
       name arguments, then for "\N{CHARNAME}" the name CHARNAME is looked up as a letter in the given
       scripts (in the specified order). Customized aliases can override these, and are explained in "CUSTOM
       ALIASES".

       For lookup of CHARNAME inside a given script SCRIPTNAME, this pragma looks in the table of standard
       Unicode names for the names

         SCRIPTNAME CAPITAL LETTER CHARNAME
         SCRIPTNAME SMALL LETTER CHARNAME
         SCRIPTNAME LETTER CHARNAME

       If CHARNAME is all lowercase, then the "CAPITAL" variant is ignored, otherwise the "SMALL" variant is
       ignored, and both CHARNAME and SCRIPTNAME are converted to all uppercase for look-up.  Other than
       that, both of them follow loose rules if ":loose" is also specified; strict otherwise.

       Note that "\N{...}" is compile-time; it's a special form of string constant used inside double-quotish doublequotish
       quotish strings; this means that you cannot use variables inside the "\N{...}".  If you want similar
       run-time functionality, use charnames::string_vianame().

       Since Unicode 6.0, it is deprecated to use "BELL".  Instead use "ALERT" (but "BEL" will continue to
       work).

       If the input name is unknown, "\N{NAME}" raises a warning and substitutes the Unicode REPLACEMENT
       CHARACTER (U+FFFD).

       For "\N{NAME}", it is a fatal error if "use bytes" is in effect and the input name is that of a
       character that won't fit into a byte (i.e., whose ordinal is above 255).

       Otherwise, any string that includes a "\N{charname}" or "\N{U+code point}" will automatically have
       Unicode semantics (see "Byte and Character Semantics" in perlunicode).

LOOSE MATCHES
       By specifying ":loose", Unicode's loose character name matching
       <http://www.unicode.org/reports/tr44#Matching_Rules> rules are selected instead of the strict exact
       match used otherwise.  That means that CHARNAME doesn't have to be so precisely specified.
       Upper/lower case doesn't matter (except with scripts as mentioned above), nor do any underscores, and
       the only hyphens that matter are those at the beginning or end of a word in the name (with one
       exception:  the hyphen in U+1180 "HANGUL JUNGSEONG O-E" does matter).  Also, blanks not adjacent to
       hyphens don't matter.  The official Unicode names are quite variable as to where they use hyphens
       versus spaces to separate word-like units, and this option allows you to not have to care as much.
       The reason non-medial hyphens matter is because of cases like U+0F60 "TIBETAN LETTER -A" versus
       U+0F68 "TIBETAN LETTER A".  The hyphen here is significant, as is the space before it, and so both
       must be included.

       ":loose" slows down look-ups by a factor of 2 to 3 versus ":full", but the trade-off may be worth it
       to you.  Each individual look-up takes very little time, and the results are cached, so the speed
       difference would become a factor only in programs that do look-ups of many different spellings, and
       probably only when those look-ups are through vianame() and string_vianame(), since "\N{...}" look-ups lookups
       ups are done at compile time.

ALIASES
       Starting in Unicode 6.1 and Perl v5.16, Unicode defines many abbreviations and names that were
       formerly Perl extensions, and some additional ones that Perl did not previously accept.  The list is
       getting too long to reproduce here, but you can get the complete list from the Unicode web site:
       <http://www.unicode.org/Public/UNIDATA/NameAliases.txt>.

       Earlier versions of Perl accepted almost all the 6.1 names.  These were most extensively documented
       in the v5.14 version of this pod: <http://perldoc.perl.org/5.14.0/charnames.html#ALIASES>.

CUSTOM ALIASES
       You can add customized aliases to standard (":full") Unicode naming conventions.  The aliases
       override any standard definitions, so, if you're twisted enough, you can change "\N{LATIN CAPITAL
       LETTER A}" to mean "B", etc.

       Note that an alias should not be something that is a legal curly brace-enclosed quantifier (see
       "QUANTIFIERS" in perlreref).  For example "\N{123}" means to match 123 non-newline characters, and is
       not treated as a charnames alias.  Aliases are discouraged from beginning with anything other than an
       alphabetic character and from containing anything other than alphanumerics, spaces, dashes,
       parentheses, and underscores.  Currently they must be ASCII.

       An alias can map to either an official Unicode character name (not a loose matched name) or to a
       numeric code point (ordinal).  The latter is useful for assigning names to code points in Unicode
       private use areas such as U+E800 through U+F8FF.  A numeric code point must be a non-negative integer
       or a string beginning with "U+" or "0x" with the remainder considered to be a hexadecimal integer.  A
       literal numeric constant must be unsigned; it will be interpreted as hex if it has a leading zero or
       contains non-decimal hex digits; otherwise it will be interpreted as decimal.

       Aliases are added either by the use of anonymous hashes:

           use charnames ":alias" => {
               e_ACUTE => "LATIN SMALL LETTER E WITH ACUTE",
               mychar1 => 0xE8000,
               };
           my $str = "\N{e_ACUTE}";

       or by using a file containing aliases:

           use charnames ":alias" => "pro";

       This will try to read "unicore/pro_alias.pl" from the @INC path. This file should return a list in
       plain perl:

           (
           A_GRAVE         => "LATIN CAPITAL LETTER A WITH GRAVE",
           A_CIRCUM        => "LATIN CAPITAL LETTER A WITH CIRCUMFLEX",
           A_DIAERES       => "LATIN CAPITAL LETTER A WITH DIAERESIS",
           A_TILDE         => "LATIN CAPITAL LETTER A WITH TILDE",
           A_BREVE         => "LATIN CAPITAL LETTER A WITH BREVE",
           A_RING          => "LATIN CAPITAL LETTER A WITH RING ABOVE",
           A_MACRON        => "LATIN CAPITAL LETTER A WITH MACRON",
           mychar2         => "U+E8001",
           );

       Both these methods insert ":full" automatically as the first argument (if no other argument is
       given), and you can give the ":full" explicitly as well, like

           use charnames ":full", ":alias" => "pro";

       ":loose" has no effect with these.  Input names must match exactly, using ":full" rules.

       Also, both these methods currently allow only single characters to be named.  To name a sequence of
       characters, use a custom translator (described below).

charnames::string_vianame(name)
       This is a runtime equivalent to "\N{...}".  name can be any expression that evaluates to a name
       accepted by "\N{...}" under the ":full" option to "charnames".  In addition, any other options for
       the controlling "use charnames" in the same scope apply, like ":loose" or any script list, ":short"
       option, or custom aliases you may have defined.

       The only difference is that if the input name is unknown, "string_vianame" returns "undef" instead of
       the REPLACEMENT CHARACTER and does not raise a warning message.

charnames::vianame(name)
       This is similar to "string_vianame".  The main difference is that under most circumstances, vianame
       returns an ordinal code point, whereas "string_vianame" returns a string.  For example,

          printf "U+%04X", charnames::vianame("FOUR TEARDROP-SPOKED ASTERISK");

       prints "U+2722".

       This leads to the other two differences.  Since a single code point is returned, the function can't
       handle named character sequences, as these are composed of multiple characters (it returns "undef"
       for these.  And, the code point can be that of any character, even ones that aren't legal under the
       "use bytes" pragma,

       See "BUGS" for the circumstances in which the behavior differs from  that described above.

charnames::viacode(code)
       Returns the full name of the character indicated by the numeric code.  For example,

           print charnames::viacode(0x2722);

       prints "FOUR TEARDROP-SPOKED ASTERISK".

       The name returned is the "best" (defined below) official name or alias for the code point, if
       available; otherwise your custom alias for it, if defined; otherwise "undef".  This means that your
       alias will only be returned for code points that don't have an official Unicode name (nor alias) such
       as private use code points.

       If you define more than one name for the code point, it is indeterminate which one will be returned.

       As mentioned, the function returns "undef" if no name is known for the code point.  In Unicode the
       proper name of these is the empty string, which "undef" stringifies to.  (If you ask for a code point
       past the legal Unicode maximum of U+10FFFF that you haven't assigned an alias to, you get "undef"
       plus a warning.)

       The input number must be a non-negative integer, or a string beginning with "U+" or "0x" with the
       remainder considered to be a hexadecimal integer.  A literal numeric constant must be unsigned; it
       will be interpreted as hex if it has a leading zero or contains non-decimal hex digits; otherwise it
       will be interpreted as decimal.

       As mentioned above under "ALIASES", Unicode 6.1 defines extra names (synonyms or aliases) for some
       code points, most of which were already available as Perl extensions.  All these are accepted by
       "\N{...}" and the other functions in this module, but "viacode" has to choose which one name to
       return for a given input code point, so it returns the "best" name.  To understand how this works, it
       is helpful to know more about the Unicode name properties.  All code points actually have only a
       single name, which (starting in Unicode 2.0) can never change once a character has been assigned to
       the code point.  But mistakes have been made in assigning names, for example sometimes a clerical
       error was made during the publishing of the Standard which caused words to be misspelled, and there
       was no way to correct those.  The Name_Alias property was eventually created to handle these
       situations.  If a name was wrong, a corrected synonym would be published for it, using Name_Alias.
       "viacode" will return that corrected synonym as the "best" name for a code point.  (It is even
       possible, though it hasn't happened yet, that the correction itself will need to be corrected, and so
       another Name_Alias can be created for that code point; "viacode" will return the most recent
       correction.)

       The Unicode name for each of the control characters (such as LINE FEED) is the empty string.  However
       almost all had names assigned by other standards, such as the ASCII Standard, or were in common use.
       "viacode" returns these names as the "best" ones available.  Unicode 6.1 has created Name_Aliases for
       each of them, including alternate names, like NEW LINE.  "viacode" uses the original name, "LINE
       FEED" in preference to the alternate.  Similarly the name returned for U+FEFF is "ZERO WIDTH NO-BREAK
       SPACE", not "BYTE ORDER MARK".

       Until Unicode 6.1, the 4 control characters U+0080, U+0081, U+0084, and U+0099 did not have names nor
       aliases.  To preserve backwards compatibility, any alias you define for these code points will be
       returned by this function, in preference to the official name.

       Some code points also have abbreviated names, such as "LF" or "NL".  "viacode" never returns these.

       Because a name correction may be added in future Unicode releases, the name that "viacode" returns
       may change as a result.  This is a rare event, but it does happen.

CUSTOM TRANSLATORS
       The mechanism of translation of "\N{...}" escapes is general and not hardwired into charnames.pm.  A
       module can install custom translations (inside the scope which "use"s the module) with the following
       magic incantation:

           sub import {
               shift;
               $^H{charnames} = \&translator;
           }

       Here translator() is a subroutine which takes CHARNAME as an argument, and returns text to insert
       into the string instead of the "\N{CHARNAME}" escape.

       This is the only way you can create a custom named sequence of code points.

       Since the text to insert should be different in "bytes" mode and out of it, the function should check
       the current state of "bytes"-flag as in:

           use bytes ();                      # for $bytes::hint_bits
           sub translator {
               if ($^H & $bytes::hint_bits) {
                   return bytes_translator(@_);
               }
               else {
                   return utf8_translator(@_);
               }
           }

       See "CUSTOM ALIASES" above for restrictions on CHARNAME.

       Of course, "vianame", "viacode", and "string_vianame" would need to be overridden as well.

BUGS
       vianame() normally returns an ordinal code point, but when the input name is of the form "U+...", it
       returns a chr instead.  In this case, if "use bytes" is in effect and the character won't fit into a
       byte, it returns "undef" and raises a warning.

       Names must be ASCII characters only, which means that you are out of luck if you want to create
       aliases in a language where some or all the characters of the desired aliases are non-ASCII.

       Since evaluation of the translation function (see "CUSTOM TRANSLATORS") happens in the middle of
       compilation (of a string literal), the translation function should not do any "eval"s or "require"s.
       This restriction should be lifted (but is low priority) in a future version of Perl.



perl v5.16.2                                     2012-10-25                                   charnames(3pm)