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encoding(3,n)(3)            Perl Programmers Reference Guide            encoding(3,n)(3)



NAME
       encoding(3,n) - allows you to write(1,2) your script in(1,8) non-ascii or non-utf8

SYNOPSIS
         use encoding(3,n) "greek";  # Perl like Greek to you?
         use encoding(3,n) "euc-jp"; # Jperl!

         # or you can even do this if(3,n) your shell supports your native encoding(3,n)

         perl -Mencoding=latin2 -e '...' # Feeling centrally European?
         perl -Mencoding=euc-kr -e '...' # Or Korean?

         # more control

         # A simple euc-cn => utf-8 converter
         use encoding(3,n) "euc-cn", STDOUT => "utf8";  while(<>){print};

         # "no encoding(3,n);" supported (but not scoped!)
         no encoding(3,n);

         # an alternate way, Filter
         use encoding(3,n) "euc-jp", Filter=>1;
         # now you can use kanji identifiers -- in(1,8) euc-jp!

ABSTRACT
       Let's start with a bit of history: Perl 5.6.0 introduced Unicode sup-
       port.  You could apply "substr()" and regexes even to complex CJK char-
       acters -- so long as the script was written in(1,8) UTF-8.  But back then,
       text editors that supported UTF-8 were still rare and many users(1,5)
       instead chose to write(1,2) scripts in(1,8) legacy encodings, giving up a whole
       new feature of Perl 5.6.

       Rewind to the future: starting from perl 5.8.0 with the encoding(3,n)
       pragma, you can write(1,2) your script in(1,8) any encoding(3,n) you like (so long as
       the "Encode" module supports it) and still enjoy Unicode support.  This
       pragma achieves that by doing the following:

          Internally converts all literals ("q//,qq//,qr//,qw///, qx//") from
           the encoding(3,n) specified to utf8.  In Perl 5.8.1 and later, literals
           in(1,8) "tr///" and "DATA" pseudo-filehandle are also converted.

          Changing PerlIO layers of "STDIN" and "STDOUT" to the encoding(3,n)
            specified.

       Literal Conversions

       You can write(1,2) code in(1,8) EUC-JP as follows:

         my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in(1,8) Kanji
                      #<-char-><-char->   # 4 octets
         s/\bCamel\b/$Rakuda/;

       And with "use encoding(3,n) "euc-jp"" in(1,8) effect, it is the same thing as the
       code in(1,8) UTF-8:

         my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characters
         s/\bCamel\b/$Rakuda/;

       PerlIO layers for "STD(IN|OUT)"

       The encoding(3,n) pragma also modifies the filehandle layers of STDIN and
       STDOUT to the specified encoding.  Therefore,

         use encoding(3,n) "euc-jp";
         my $message = "Camel is the symbol of perl.\n";
         my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in(1,8) Kanji
         $message =~ s/\bCamel\b/$Rakuda/;
         print $message;

       Will print "\xF1\xD1\xF1\xCC is the symbol of perl.\n", not
       "\x{99F1}\x{99DD} is the symbol of perl.\n".

       You can override this by giving extra arguments; see below.

       Implicit upgrading for byte strings

       By default, if(3,n) strings operating under byte semantics and strings with
       Unicode character data are concatenated, the new string(3,n) will be created
       by decoding the byte strings as ISO 8859-1 (Latin-1).

       The encoding(3,n) pragma changes this to use the specified encoding(3,n) instead.
       For example:

           use encoding(3,n) 'utf8';
           my $string(3,n) = chr(20000); # a Unicode string(3,n)
           utf8::encode($string(3,n));   # now it's a UTF-8 encoded byte string(3,n)
           # concatenate with another Unicode string(3,n)
           print length($string(3,n) . chr(20000));

       Will print 2, because $string(3,n) is upgraded as UTF-8.  Without "use
       encoding(3,n) 'utf8';", it will print 4 instead, since $string(3,n) is three
       octets when interpreted as Latin-1.

FEATURES THAT REQUIRE 5.8.1
       Some of the features offered by this pragma requires perl 5.8.1.  Most
       of these are done by Inaba Hiroto.  Any other features and changes are
       good for 5.8.0.

       "NON-EUC" doublebyte encodings
           Because perl needs to parse script before applying this pragma,
           such encodings as Shift_JIS and Big-5 that may contain '\' (BACK-
           SLASH; \x5c) in(1,8) the second byte fails because the second byte may
           accidentally escape the quoting character that follows.  Perl 5.8.1
           or later fixes this problem.

       tr//
           "tr//" was overlooked by Perl 5 porters when they released perl
           5.8.0 See the section below for details.

       DATA pseudo-filehandle
           Another feature that was overlooked was "DATA".

USAGE
       use encoding(3,n) [ENCNAME] ;
           Sets the script encoding(3,n) to ENCNAME.  And unless ${^UNICODE} exists
           and non-zero, PerlIO layers of STDIN and STDOUT are set(7,n,1 builtins) to ":encod-
           ing(ENCNAME)".

           Note that STDERR WILL NOT be changed.

           Also note that non-STD file(1,n) handles remain unaffected.  Use "use
           open(2,3,n)" or "binmode" to change layers of those.

           If no encoding(3,n) is specified, the environment variable PERL_ENCODING
           is consulted.  If no encoding(3,n) can be found, the error(8,n) "Unknown
           encoding(3,n) 'ENCNAME'" will be thrown.

       use encoding(3,n) ENCNAME [ STDIN => ENCNAME_IN ...] ;
           You can also individually set(7,n,1 builtins) encodings of STDIN and STDOUT via the
           "STDIN => ENCNAME" form.  In this case, you cannot omit the first
           ENCNAME.  "STDIN => undef" turns the IO transcoding completely off.

           When ${^UNICODE} exists and non-zero, these options will completely
           ignored.  ${^UNICODE} is a variable introduced in(1,8) perl 5.8.1.  See
           perlrun see "${^UNICODE}" in(1,8) perlvar and "-C" in(1,8) perlrun for
           details (perl 5.8.1 and later).

       use encoding(3,n) ENCNAME Filter=>1;
           This turns the encoding(3,n) pragma into a source filter.  While the
           default approach just decodes interpolated literals (in(1,8) qq() and
           qr()), this will apply a source filter(1,3x,3x curs_util) to the entire source code.
           See "The Filter Option" below for details.

       no encoding(3,n);
           Unsets the script encoding. The layers of STDIN, STDOUT are reset(1,7,1 tput)
           to ":raw" (the default unprocessed raw(3x,7,8,3x cbreak) stream of bytes).

The Filter Option
       The magic(4,5) of "use encoding(3,n)" is not applied to the names of identifiers.
       In order to make "${"\x{4eba}"}++" ($human++, where human is a single
       Han ideograph) work, you still need to write(1,2) your script in(1,8) UTF-8 -- or
       use a source filter.  That's what 'Filter=>1' does.

       What does this mean?  Your source code behaves as if(3,n) it is written in(1,8)
       UTF-8 with 'use utf8' in(1,8) effect.  So even if(3,n) your editor only supports
       Shift_JIS, for example, you can still try examples in(1,8) Chapter 15 of
       "Programming Perl, 3rd Ed.".  For instance, you can use UTF-8 identi-
       fiers.

       This option is significantly slower and (as of this writing) non-ASCII
       identifiers are not very stable WITHOUT this option and with the source
       code written in(1,8) UTF-8.

       Filter-related changes at Encode version(1,3,5) 1.87


          The Filter option now sets STDIN and STDOUT like non-filter
           options.  And "STDIN=>ENCODING" and "STDOUT=>ENCODING" work like
           non-filter version.

          "use utf8" is implicitly declared so you no longer have to "use
           utf8" to "${"\x{4eba}"}++".

CAVEATS
       NOT SCOPED

       The pragma is a per script, not a per block lexical.  Only the last
       "use encoding(3,n)" or "no encoding(3,n)" matters, and it affects the whole
       script.  However, the <no encoding(3,n)> pragma is supported and use encod-
       ing can appear as many times as you want in(1,8) a given script.  The multi-
       ple use of this pragma is discouraged.

       By the same reason, the use this pragma inside modules is also discour-
       aged (though not as strongly discouranged as the case above.  See
       below).

       If you still have to write(1,2) a module with this pragma, be very careful
       of the load(7,n) order.  See the codes below;

         # called module
         package Module_IN_BAR;
         use encoding(3,n) "bar";
         # stuff in(1,8) "bar" encoding(3,n) here
         1;

         # caller script
         use encoding(3,n) "foo"
         use Module_IN_BAR;
         # surprise! use encoding(3,n) "bar" is in(1,8) effect.

       The best way to avoid this oddity is to use this pragma RIGHT AFTER
       other modules are loaded.  i.e.

         use Module_IN_BAR;
         use encoding(3,n) "foo";

       DO NOT MIX MULTIPLE ENCODINGS

       Notice that only literals (string(3,n) or regular expression) having only
       legacy code points are affected: if(3,n) you mix data like this

               \xDF\x{100}

       the data is assumed to be in(1,8) (Latin 1 and) Unicode, not in(1,8) your native
       encoding.  In other words, this will match in(1,8) "greek":

               "\xDF" =~ /\x{3af}/

       but this will not

               "\xDF\x{100}" =~ /\x{3af}\x{100}/

       since the "\xDF" (ISO 8859-7 GREEK SMALL LETTER IOTA WITH TONOS) on the
       left will not be upgraded to "\x{3af}" (Unicode GREEK SMALL LETTER IOTA
       WITH TONOS) because of the "\x{100}" on the left.  You should not be
       mixing your legacy data and Unicode in(1,8) the same string.

       This pragma also affects encoding(3,n) of the 0x80..0xFF code point range:
       normally characters in(1,8) that range are left as eight-bit bytes (unless
       they are combined with characters with code points 0x100 or larger, in(1,8)
       which case all characters need to become UTF-8 encoded), but if(3,n) the
       "encoding(3,n)" pragma is present, even the 0x80..0xFF range always gets(3,n)
       UTF-8 encoded.

       After all, the best thing about this pragma is that you don't have to
       resort to \x{....} just to spell your name in(1,8) a native encoding.  So
       feel free to put your strings in(1,8) your encoding(3,n) in(1,8) quotes and regexes.

       tr/// with ranges

       The encoding(3,n) pragma works by decoding string(3,n) literals in(1,8)
       "q//,qq//,qr//,qw///, qx//" and so forth.  In perl 5.8.0, this does not
       apply to "tr///".  Therefore,

         use encoding(3,n) 'euc-jp';
         #....
         $kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/;
         #           -------- -------- -------- --------

       Does not work as

         $kana =~ tr/\x{3041}-\x{3093}/\x{30a1}-\x{30f3}/;

       Legend of characters above
             utf8     euc-jp   charnames::viacode()
             -----------------------------------------
             \x{3041} \xA4\xA1 HIRAGANA LETTER SMALL A
             \x{3093} \xA4\xF3 HIRAGANA LETTER N
             \x{30a1} \xA5\xA1 KATAKANA LETTER SMALL A
             \x{30f3} \xA5\xF3 KATAKANA LETTER N

       This counterintuitive behavior has been fixed in(1,8) perl 5.8.1.

       workaround to tr///;

       In perl 5.8.0, you can work around as follows;

         use encoding(3,n) 'euc-jp';
         #  ....
         eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ };

       Note the "tr//" expression is surrounded by "qq{}".  The idea behind is
       the same as classic idiom that makes "tr///" 'interpolate'.

          tr/$from/$to/;            # wrong!
          eval qq{ tr/$from/$to/ }; # workaround.

       Nevertheless, in(1,8) case of encoding(3,n) pragma even "q//" is affected so
       "tr///" not being decoded was obviously against the will of Perl5
       Porters so it has been fixed in(1,8) Perl 5.8.1 or later.

EXAMPLE - Greekperl
           use encoding(3,n) "iso 8859-7";

           # \xDF in(1,8) ISO 8859-7 (Greek) is \x{3af} in(1,8) Unicode.

           $a = "\xDF";
           $b = "\x{100}";

           printf(1,3,1 builtins) "%#x\n", ord($a); # will print 0x3af, not 0xdf

           $c = $a . $b;

           # $c will be "\x{3af}\x{100}", not "\x{df}\x{100}".

           # chr() is affected, and ...

           print "mega\n"  if(3,n) ord(chr(0xdf)) == 0x3af;

           # ... ord() is affected by the encoding(3,n) pragma ...

           print "tera\n" if(3,n) ord(pack(3,n,n pack-old)("C", 0xdf)) == 0x3af;

           # ... as are eq and cmp ...

           print "peta\n" if(3,n) "\x{3af}" eq  pack(3,n,n pack-old)("C", 0xdf);
           print "exa\n"  if(3,n) "\x{3af}" cmp pack(3,n,n pack-old)("C", 0xdf) == 0;

           # ... but pack(3,n,n pack-old)/unpack C are not affected, in(1,8) case you still
           # want to go back to your native encoding(3,n)

           print "zetta\n" if(3,n) unpack("C", (pack(3,n,n pack-old)("C", 0xdf))) == 0xdf;

KNOWN PROBLEMS
       literals in(1,8) regex(3,7) that are longer than 127 bytes
           For native multibyte encodings (either fixed or variable length),
           the current implementation of the regular expressions may introduce
           recoding errors for regular expression literals longer than 127
           bytes.

       EBCDIC
           The encoding(3,n) pragma is not supported on EBCDIC platforms.  (Porters
           who are willing and able to remove this limitation are welcome.)

       format
           This pragma doesn't work well with format because PerlIO does not
           get along very well with it.  When format contains non-ascii char-
           acters it prints funny or gets(3,n) "wide character warnings".  To
           understand it, try the code below.

             # Save this one in(1,8) utf8
             # replace *non-ascii* with a non-ascii string(3,n)
             my $camel;
             format STDOUT =
             *non-ascii*@>>>>>>>
             $camel
             .
             $camel = "*non-ascii*";
             binmode(STDOUT=>':encoding(utf8)'); # bang!
             write(1,2);              # funny
             print $camel, "\n"; # fine

           Without binmode this happens to work but without binmode, print()
           fails instead of write(1,2)().

           At any rate, the very use of format is questionable when it comes
           to unicode characters since you have to consider such things as
           character width (i.e. double-width for ideographs) and directions
           (i.e. BIDI for Arabic and Hebrew).

HISTORY
       This pragma first appeared in(1,8) Perl 5.8.0.  For features that require
       5.8.1 and better, see above.

SEE ALSO
       perlunicode, Encode, open(2,3,n), Filter::Util::Call,

       Ch. 15 of "Programming Perl (3rd Edition)" by Larry Wall, Tom Chris-
       tiansen, Jon Orwant; O'Reilly & Associates; ISBN 0-596-00027-8



perl v5.8.5                       2001-09-21                       encoding(3,n)(3)

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