$name = $enc->name; # canonize
unless ( $arg{Filter} ) {
DEBUG and warn "_exception($name) = ", _exception($name);
- _exception($name) or ${^ENCODING} = $enc;
+ if (! _exception($name)) {
+ if (!$^V || $^V lt v5.21.7) {
+ ${^ENCODING} = $enc;
+ }
+ else {
+ # Starting with 5.21.7, this pragma uses a shadow variable
+ # designed explicitly for it, ${^E_NCODING}, to enforce
+ # lexical scope; instead of ${^ENCODING}.
+ $^H{'encoding'} = 1;
+ ${^E_NCODING} = $enc;
+ }
+ }
$HAS_PERLIO or return 1;
}
else {
defined( ${^ENCODING} ) and undef ${^ENCODING};
+ undef ${^E_NCODING} if $^V && $^V ge v5.21.7;
# implicitly 'use utf8'
require utf8; # to fetch $utf8::hint_bits;
sub unimport {
no warnings;
undef ${^ENCODING};
+ undef ${^E_NCODING} if $^V && $^V ge v5.21.7;
if ($HAS_PERLIO) {
binmode( STDIN, ":raw" );
binmode( STDOUT, ":raw" );
=head1 NAME
-encoding - allows you to write your script in non-ascii or non-utf8
+encoding - allows you to write your script in non-ASCII and non-UTF-8
=head1 WARNING
-This module is deprecated under perl 5.18. It uses a mechanism provided by
-perl that is deprecated under 5.18 and higher, and may be removed in a
-future version.
-
-The easiest and the best alternative is to write your script in UTF-8
-and declear:
-
- use utf8; # not use encoding ':utf8';
-
-See L<perluniintro> and L<utf8> for details.
+This module has been deprecated since perl v5.18. See L</DESCRIPTION> and
+L</BUGS>.
=head1 SYNOPSIS
# A simple euc-cn => utf-8 converter
use encoding "euc-cn", STDOUT => "utf8"; while(<>){print};
- # "no encoding;" supported (but not scoped!)
+ # "no encoding;" supported
no encoding;
# an alternate way, Filter
use encoding "euc-jp", Filter=>1;
# now you can use kanji identifiers -- in euc-jp!
- # switch on locale -
- # note that this probably means that unless you have a complete control
- # over the environments the application is ever going to be run, you should
- # NOT use the feature of encoding pragma allowing you to write your script
- # in any recognized encoding because changing locale settings will wreck
- # the script; you can of course still use the other features of the pragma.
+ # encode based on the current locale - specialized purposes only;
+ # fraught with danger!!
use encoding ':locale';
-=head1 ABSTRACT
+=head1 DESCRIPTION
-Let's start with a bit of history: Perl 5.6.0 introduced Unicode
-support. You could apply C<substr()> and regexes even to complex CJK
-characters -- so long as the script was written in UTF-8. But back
-then, text editors that supported UTF-8 were still rare and many users
-instead chose to write scripts in legacy encodings, giving up a whole
-new feature of Perl 5.6.
+This pragma is used to enable a Perl script to be written in encodings that
+aren't strictly ASCII nor UTF-8. It translates all or portions of the Perl
+program script from a given encoding into UTF-8, and changes the PerlIO layers
+of C<STDIN> and C<STDOUT> to the encoding specified.
-Rewind to the future: starting from perl 5.8.0 with the B<encoding>
-pragma, you can write your script in any encoding you like (so long
-as the C<Encode> module supports it) and still enjoy Unicode support.
-This pragma achieves that by doing the following:
+This pragma dates from the days when UTF-8-enabled editors were uncommon. But
+that was long ago, and the need for it is greatly diminished. That, coupled
+with the fact that it doesn't work with threads, along with other problems,
+(see L</BUGS>) have led to its being deprecated. It is planned to remove this
+pragma in a future Perl version. New code should be written in UTF-8, and the
+C<use utf8> pragma used instead (see L<perluniintro> and L<utf8> for details).
+Old code should be converted to UTF-8, via something like the recipe in the
+L</SYNOPSIS> (though this simple approach may require manual adjustments
+afterwards).
-=over
+The only legitimate use of this pragma is almost certainly just one per file,
+near the top, with file scope, as the file is likely going to only be written
+in one encoding. Further restrictions apply in Perls before v5.22 (see
+L</Prior to Perl v5.22>).
-=item *
+There are two basic modes of operation (plus turning if off):
-Internally converts all literals (C<q//,qq//,qr//,qw///, qx//>) from
-the encoding specified to utf8. In Perl 5.8.1 and later, literals in
-C<tr///> and C<DATA> pseudo-filehandle are also converted.
+=over 4
-=item *
+=item C<use encoding ['I<ENCNAME>'] ;>
-Changing PerlIO layers of C<STDIN> and C<STDOUT> to the encoding
- specified.
+This is the normal operation. It translates various literals encountered in
+the Perl source file from the encoding I<ENCNAME> into UTF-8, and similarly
+converts character code points. This is used when the script is a combination
+of ASCII (for the variable names and punctuation, I<etc>), but the literal
+data is in the specified encoding.
-=back
+I<ENCNAME> is optional. If omitted, the encoding specified in the environment
+variable L<C<PERL_ENCODING>|perlrun/PERL_ENCODING> is used. If this isn't
+set, or the resolved-to encoding is not known to C<L<Encode>>, the error
+C<Unknown encoding 'I<ENCNAME>'> will be thrown.
-=head2 Literal Conversions
+Starting in Perl v5.8.6 (C<Encode> version 2.0.1), I<ENCNAME> may be the
+name C<:locale>. This is for very specialized applications, and is documented
+in L</The C<:locale> sub-pragma> below.
-You can write code in EUC-JP as follows:
+The literals that are converted are C<q//, qq//, qr//, qw///, qx//>, and
+starting in v5.8.1, C<tr///>. Operations that do conversions include C<chr>,
+C<ord>, C<utf8::upgrade> (but not C<utf8::downgrade>), and C<chomp>.
+
+Also starting in v5.8.1, the C<DATA> pseudo-filehandle is translated from the
+encoding into UTF-8.
+
+For example, you can write code in EUC-JP as follows:
my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji
#<-char-><-char-> # 4 octets
s/\bCamel\b/$Rakuda/;
And with C<use encoding "euc-jp"> in effect, it is the same thing as
-the code in UTF-8:
+that code in UTF-8:
my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characters
s/\bCamel\b/$Rakuda/;
-=head2 PerlIO layers for C<STD(IN|OUT)>
+See L</EXAMPLE> below for a more complete example.
-The B<encoding> pragma also modifies the filehandle layers of
-STDIN and STDOUT to the specified encoding. Therefore,
+Unless C<${^UNICODE}> (available starting in v5.8.2) exists and is non-zero, the
+PerlIO layers of C<STDIN> and C<STDOUT> are set to "C<:encoding(I<ENCNAME>)>".
+Therefore,
use encoding "euc-jp";
my $message = "Camel is the symbol of perl.\n";
$message =~ s/\bCamel\b/$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.
-
-=head2 Implicit upgrading for byte strings
-
-By default, if strings operating under byte semantics and strings
-with Unicode character data are concatenated, the new string will
-be created by decoding the byte strings as I<ISO 8859-1 (Latin-1)>.
-
-The B<encoding> pragma changes this to use the specified encoding
-instead. For example:
+will print
- use encoding 'utf8';
- my $string = chr(20000); # a Unicode string
- utf8::encode($string); # now it's a UTF-8 encoded byte string
- # concatenate with another Unicode string
- print length($string . chr(20000));
+ "\xF1\xD1\xF1\xCC is the symbol of perl.\n"
-Will print C<2>, because C<$string> is upgraded as UTF-8. Without
-C<use encoding 'utf8';>, it will print C<4> instead, since C<$string>
-is three octets when interpreted as Latin-1.
+not
-=head2 Side effects
+ "\x{99F1}\x{99DD} is the symbol of perl.\n"
-If the C<encoding> pragma is in scope then the lengths returned are
-calculated from the length of C<$/> in Unicode characters, which is not
-always the same as the length of C<$/> in the native encoding.
+You can override this by giving extra arguments; see below.
-This pragma affects utf8::upgrade, but not utf8::downgrade.
+Note that C<STDERR> WILL NOT be changed, regardless.
-=head1 FEATURES THAT REQUIRE 5.8.1
+Also note that non-STD file handles remain unaffected. Use C<use
+open> or C<binmode> to change the layers of those.
-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.
+=item C<use encoding I<ENCNAME> Filter=E<gt>1;>
-=over
+This operates as above, but the C<Filter> argument with a non-zero
+value causes the entire script, and not just literals, to be translated from
+the encoding into UTF-8. This allows identifiers in the source to be in that
+encoding as well. (Problems may occur if the encoding is not a superset of
+ASCII; imagine all your semi-colons being translated into something
+different.) One can use this form to make
-=item "NON-EUC" doublebyte encodings
+ ${"\x{4eba}"}++
-Because perl needs to parse script before applying this pragma, such
-encodings as Shift_JIS and Big-5 that may contain '\' (BACKSLASH;
-\x5c) in the second byte fails because the second byte may
-accidentally escape the quoting character that follows. Perl 5.8.1
-or later fixes this problem.
+work. (This is equivalent to C<$I<human>++>, where I<human> is a single Han
+ideograph).
-=item tr//
+This effectively means that your source code behaves as if it were written in
+UTF-8 with C<'use utf8>' in effect. So even if your editor only supports
+Shift_JIS, for example, you can still try examples in Chapter 15 of
+C<Programming Perl, 3rd Ed.>.
-C<tr//> was overlooked by Perl 5 porters when they released perl 5.8.0
-See the section below for details.
+This option is significantly slower than the other one.
-=item DATA pseudo-filehandle
+=item C<no encoding;>
-Another feature that was overlooked was C<DATA>.
+Unsets the script encoding. The layers of C<STDIN>, C<STDOUT> are
+reset to "C<:raw>" (the default unprocessed raw stream of bytes).
=back
-=head1 USAGE
+=head1 OPTIONS
-=over 4
+=head2 Setting C<STDIN> and/or C<STDOUT> individually
-=item use encoding [I<ENCNAME>] ;
+The encodings of C<STDIN> and C<STDOUT> are individually settable by parameters to
+the pragma:
-Sets the script encoding to I<ENCNAME>. And unless ${^UNICODE}
-exists and non-zero, PerlIO layers of STDIN and STDOUT are set to
-":encoding(I<ENCNAME>)".
+ use encoding 'euc-tw', STDIN => 'greek' ...;
-Note that STDERR WILL NOT be changed.
+In this case, you cannot omit the first I<ENCNAME>. C<< STDIN => undef >>
+turns the I/O transcoding completely off for that filehandle.
-Also note that non-STD file handles remain unaffected. Use C<use
-open> or C<binmode> to change layers of those.
+When C<${^UNICODE}> (available starting in v5.8.2) exists and is non-zero,
+these options will be completely ignored. See L<perlvar/C<${^UNICODE}>> and
+L<"C<-C>" in perlrun|perlrun/-C [numberE<sol>list]> for details.
-If no encoding is specified, the environment variable L<PERL_ENCODING>
-is consulted. If no encoding can be found, the error C<Unknown encoding
-'I<ENCNAME>'> will be thrown.
+=head2 The C<:locale> sub-pragma
-=item use encoding I<ENCNAME> [ STDIN =E<gt> I<ENCNAME_IN> ...] ;
+Starting in v5.8.6, the encoding name may be C<:locale>. This means that the
+encoding is taken from the current locale, and not hard-coded by the pragma.
+Since a script really can only be encoded in exactly one encoding, this option
+is dangerous. It makes sense only if the script itself is written in ASCII,
+and all the possible locales that will be in use when the script is executed
+are supersets of ASCII. That means that the script itself doesn't get
+changed, but the I/O handles have the specified encoding added, and the
+operations like C<chr> and C<ord> use that encoding.
-You can also individually set encodings of STDIN and STDOUT via the
-C<< STDIN => I<ENCNAME> >> form. In this case, you cannot omit the
-first I<ENCNAME>. C<< STDIN => undef >> turns the IO transcoding
-completely off.
+The logic of finding which locale C<:locale> uses is as follows:
-When ${^UNICODE} exists and non-zero, these options will completely
-ignored. ${^UNICODE} is a variable introduced in perl 5.8.1. See
-L<perlrun> see L<perlvar/"${^UNICODE}"> and L<perlrun/"-C"> for
-details (perl 5.8.1 and later).
+=over 4
-=item use encoding I<ENCNAME> Filter=E<gt>1;
+=item 1.
-This turns the encoding pragma into a source filter. While the
-default approach just decodes interpolated literals (in qq() and
-qr()), this will apply a source filter to the entire source code. See
-L</"The Filter Option"> below for details.
+If the platform supports the C<langinfo(CODESET)> interface, the codeset
+returned is used as the default encoding for the open pragma.
-=item no encoding;
+=item 2.
-Unsets the script encoding. The layers of STDIN, STDOUT are
-reset to ":raw" (the default unprocessed raw stream of bytes).
+If 1. didn't work but we are under the locale pragma, the environment
+variables C<LC_ALL> and C<LANG> (in that order) are matched for encodings
+(the part after "C<.>", if any), and if any found, that is used
+as the default encoding for the open pragma.
-=back
+=item 3.
-=head1 The Filter Option
+If 1. and 2. didn't work, the environment variables C<LC_ALL> and C<LANG>
+(in that order) are matched for anything looking like UTF-8, and if
+any found, C<:utf8> is used as the default encoding for the open
+pragma.
-The magic of C<use encoding> is not applied to the names of
-identifiers. In order to make C<${"\x{4eba}"}++> ($human++, where human
-is a single Han ideograph) work, you still need to write your script
-in UTF-8 -- or use a source filter. That's what 'Filter=>1' does.
+=back
-What does this mean? Your source code behaves as if it is written in
-UTF-8 with 'use utf8' in effect. So even if your editor only supports
-Shift_JIS, for example, you can still try examples in Chapter 15 of
-C<Programming Perl, 3rd Ed.>. For instance, you can use UTF-8
-identifiers.
+If your locale environment variables (C<LC_ALL>, C<LC_CTYPE>, C<LANG>)
+contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching),
+the default encoding of your C<STDIN>, C<STDOUT>, and C<STDERR>, and of
+B<any subsequent file open>, is UTF-8.
-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 UTF-8.
+=head1 CAVEATS
-=head2 Filter-related changes at Encode version 1.87
+=head2 SIDE EFFECTS
=over
=item *
-The Filter option now sets STDIN and STDOUT like non-filter options.
-And C<< STDIN=>I<ENCODING> >> and C<< STDOUT=>I<ENCODING> >> work like
-non-filter version.
+If the C<encoding> pragma is in scope then the lengths returned are
+calculated from the length of C<$/> in Unicode characters, which is not
+always the same as the length of C<$/> in the native encoding.
=item *
-C<use utf8> is implicitly declared so you no longer have to C<use
-utf8> to C<${"\x{4eba}"}++>.
-
-=back
-
-=head1 CAVEATS
-
-=head2 NOT SCOPED
-
-The pragma is a per script, not a per block lexical. Only the last
-C<use encoding> or C<no encoding> matters, and it affects
-B<the whole script>. However, the <no encoding> pragma is supported and
-B<use encoding> can appear as many times as you want in a given script.
-The multiple use of this pragma is discouraged.
-
-By the same reason, the use this pragma inside modules is also
-discouraged (though not as strongly discouraged as the case above.
-See below).
-
-If you still have to write a module with this pragma, be very careful
-of the load order. See the codes below;
+Without this pragma, if strings operating under byte semantics and strings
+with Unicode character data are concatenated, the new string will
+be created by decoding the byte strings as I<ISO 8859-1 (Latin-1)>.
- # called module
- package Module_IN_BAR;
- use encoding "bar";
- # stuff in "bar" encoding here
- 1;
+The B<encoding> pragma changes this to use the specified encoding
+instead. For example:
- # caller script
- use encoding "foo"
- use Module_IN_BAR;
- # surprise! use encoding "bar" is in effect.
+ use encoding 'utf8';
+ my $string = chr(20000); # a Unicode string
+ utf8::encode($string); # now it's a UTF-8 encoded byte string
+ # concatenate with another Unicode string
+ print length($string . chr(20000));
-The best way to avoid this oddity is to use this pragma RIGHT AFTER
-other modules are loaded. i.e.
+Will print C<2>, because C<$string> is upgraded as UTF-8. Without
+C<use encoding 'utf8';>, it will print C<4> instead, since C<$string>
+is three octets when interpreted as Latin-1.
- use Module_IN_BAR;
- use encoding "foo";
+=back
=head2 DO NOT MIX MULTIPLE ENCODINGS
Notice that only literals (string or regular expression) having only
legacy code points are affected: if you mix data like this
+ \x{100}\xDF
\xDF\x{100}
the data is assumed to be in (Latin 1 and) Unicode, not in your native
So feel free to put your strings in your encoding in quotes and
regexes.
-=head2 tr/// with ranges
+=head2 Prior to Perl v5.22
+
+The pragma was a per script, not a per block lexical. Only the last
+C<use encoding> or C<no encoding> mattered, and it affected
+B<the whole script>. However, the C<no encoding> pragma was supported and
+C<use encoding> could appear as many times as you want in a given script
+(though only the last was effective).
+
+Since the scope wasn't lexical, other modules' use of C<chr>, C<ord>, I<etc.>
+were affected. This leads to spooky, incorrect action at a distance that is
+hard to debug.
+
+This means you would have to be very careful of the load order:
+
+ # called module
+ package Module_IN_BAR;
+ use encoding "bar";
+ # stuff in "bar" encoding here
+ 1;
+
+ # caller script
+ use encoding "foo"
+ use Module_IN_BAR;
+ # surprise! use encoding "bar" is in 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 "foo";
+
+=head2 Prior to Encode version 1.87
+
+=over
+
+=item *
+
+C<STDIN> and C<STDOUT> were not set under the filter option.
+And C<< STDIN=>I<ENCODING> >> and C<< STDOUT=>I<ENCODING> >> didn't work like
+non-filter version.
+
+=item *
+
+C<use utf8> wasn't implicitly declared so you have to C<use utf8> to do
+
+ ${"\x{4eba}"}++
+
+=back
+
+=head2 Prior to Perl v5.8.1
+
+=over
+
+=item "NON-EUC" doublebyte encodings
+
+Because perl needs to parse the script before applying this pragma, such
+encodings as Shift_JIS and Big-5 that may contain C<'\'> (BACKSLASH;
+C<\x5c>) in the second byte fail because the second byte may
+accidentally escape the quoting character that follows.
+
+=item C<tr///>
The B<encoding> pragma works by decoding string literals in
-C<q//,qq//,qr//,qw///, qx//> and so forth. In perl 5.8.0, this
+C<q//,qq//,qr//,qw///, qx//> and so forth. In perl v5.8.0, this
does not apply to C<tr///>. Therefore,
use encoding 'euc-jp';
=back
-This counterintuitive behavior has been fixed in perl 5.8.1.
+This counterintuitive behavior has been fixed in perl v5.8.1.
-=head3 workaround to tr///;
-
-In perl 5.8.0, you can work around as follows;
+In perl v5.8.0, you can work around this as follows;
use encoding 'euc-jp';
# ....
eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ };
Note the C<tr//> expression is surrounded by C<qq{}>. The idea behind
-is the same as classic idiom that makes C<tr///> 'interpolate'.
+this is the same as the classic idiom that makes C<tr///> 'interpolate':
tr/$from/$to/; # wrong!
eval qq{ tr/$from/$to/ }; # workaround.
-Nevertheless, in case of B<encoding> pragma even C<q//> is affected so
-C<tr///> not being decoded was obviously against the will of Perl5
-Porters so it has been fixed in Perl 5.8.1 or later.
+=back
=head1 EXAMPLE - Greekperl
print "zetta\n" if unpack("C", (pack("C", 0xdf))) == 0xdf;
-=head1 KNOWN PROBLEMS
+=head1 BUGS
=over
+=item Thread safety
+
+C<use encoding ...> is not thread-safe (i.e., do not use in threaded
+applications).
+
+=item Can't be used by more than one module in a single program.
+
+Only one encoding is allowed. If you combine modules in a program that have
+different encodings, only one will be actually used.
+
+=item Other modules using C<STDIN> and C<STDOUT> get the encoded stream
+
+They may be expecting something completely different.
+
=item literals in regex that are longer than 127 bytes
For native multibyte encodings (either fixed or variable length),
=item EBCDIC
The encoding pragma is not supported on EBCDIC platforms.
-(Porters who are willing and able to remove this limitation are
-welcome.)
-=item format
+=item C<format>
-This pragma doesn't work well with format because PerlIO does not
-get along very well with it. When format contains non-ascii
+This pragma doesn't work well with C<format> because PerlIO does not
+get along very well with it. When C<format> contains non-ASCII
characters it prints funny or gets "wide character warnings".
To understand it, try the code below.
Without binmode this happens to work but without binmode, print()
fails instead of write().
-At any rate, the very use of format is questionable when it comes to
+At any rate, the very use of C<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).
-=item Thread safety
-
-C<use encoding ...> is not thread-safe (i.e., do not use in threaded
-applications).
+=item See also L</CAVEATS>
=back
-=head2 The Logic of :locale
-
-The logic of C<:locale> is as follows:
-
-=over 4
-
-=item 1.
-
-If the platform supports the langinfo(CODESET) interface, the codeset
-returned is used as the default encoding for the open pragma.
-
-=item 2.
-
-If 1. didn't work but we are under the locale pragma, the environment
-variables LC_ALL and LANG (in that order) are matched for encodings
-(the part after C<.>, if any), and if any found, that is used
-as the default encoding for the open pragma.
-
-=item 3.
-
-If 1. and 2. didn't work, the environment variables LC_ALL and LANG
-(in that order) are matched for anything looking like UTF-8, and if
-any found, C<:utf8> is used as the default encoding for the open
-pragma.
-
-=back
-
-If your locale environment variables (LC_ALL, LC_CTYPE, LANG)
-contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching),
-the default encoding of your STDIN, STDOUT, and STDERR, and of
-B<any subsequent file open>, is UTF-8.
-
=head1 HISTORY
-This pragma first appeared in Perl 5.8.0. For features that require
-5.8.1 and better, see above.
-
-The C<:locale> subpragma was implemented in 2.01, or Perl 5.8.6.
+This pragma first appeared in Perl v5.8.0. It has been enhanced in later
+releases as specified above.
=head1 SEE ALSO
https://perl5.git.perl.org / perl5.git / commitdiff