| encoding - allows you to write your script in non-ASCII and non-UTF-8 |
encoding - allows you to write your script in non-ASCII and non-UTF-8
This module has been deprecated since perl v5.18. See DESCRIPTION and BUGS.
use encoding "greek"; # Perl like Greek to you? use encoding "euc-jp"; # Jperl!
# or you can even do this if your shell supports your native encoding
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 "euc-cn", STDOUT => "utf8"; while(<>){print};
# "no encoding;" supported no encoding;
# an alternate way, Filter use encoding "euc-jp", Filter=>1; # now you can use kanji identifiers -- in euc-jp!
# encode based on the current locale - specialized purposes only; # fraught with danger!! use encoding ':locale';
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 STDIN and STDOUT to the encoding specified.
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 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
use utf8 pragma used instead (see the perluniintro manpage and the utf8 manpage for details).
Old code should be converted to UTF-8, via something like the recipe in the
SYNOPSIS (though this simple approach may require manual adjustments
afterwards).
If UTF-8 is not an option, it is recommended that one use a simple source
filter, such as that provided by the Filter::Encoding manpage on CPAN or this
pragma's own Filter option (see below).
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 Prior to Perl v5.22).
There are two basic modes of operation (plus turning if off):
use encoding ['ENCNAME'] ;This is the normal operation. It translates various literals encountered in the Perl source file from the encoding 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, etc), but the literal data is in the specified encoding.
ENCNAME is optional. If omitted, the encoding specified in the environment
variable PERL_ENCODING is used. If this isn't
set, or the resolved-to encoding is not known to Encode, the error
Unknown encoding 'ENCNAME' will be thrown.
Starting in Perl v5.8.6 (Encode version 2.0.1), ENCNAME may be the
name :locale. This is for very specialized applications, and is documented
in The :locale sub-pragma below.
The literals that are converted are q//, qq//, qr//, qw///, qx//, and
starting in v5.8.1, tr///. Operations that do conversions include chr,
ord, utf8::upgrade (but not utf8::downgrade), and chomp.
Also starting in v5.8.1, the 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 use encoding "euc-jp" in effect, it is the same thing as
that code in UTF-8:
my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characters
s/\bCamel\b/$Rakuda/;
See EXAMPLE below for a more complete example.
Unless ${^UNICODE} (available starting in v5.8.2) exists and is non-zero, the
PerlIO layers of STDIN and STDOUT are set to ``:encoding(ENCNAME)''.
Therefore,
use encoding "euc-jp"; my $message = "Camel is the symbol of perl.\n"; my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in 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.
Note that STDERR WILL NOT be changed, regardless.
Also note that non-STD file handles remain unaffected. Use use
open or binmode to change the layers of those.
use encoding ENCNAME, Filter=>1;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
${"\x{4eba}"}++
work. (This is equivalent to $human++, where human is a single Han
ideograph).
This effectively means that your source code behaves as if it were 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
Programming Perl, 3rd Ed..
This option is significantly slower than the other one.
no encoding;STDIN, STDOUT are
reset to ``:raw'' (the default unprocessed raw stream of bytes).
STDIN and/or STDOUT individuallyThe encodings of STDIN and STDOUT are individually settable by parameters to
the pragma:
use encoding 'euc-tw', STDIN => 'greek' ...;
In this case, you cannot omit the first ENCNAME. STDIN => undef
turns the I/O transcoding completely off for that filehandle.
When ${^UNICODE} (available starting in v5.8.2) exists and is non-zero,
these options will be completely ignored. See ${^UNICODE} in the perlvar manpage and
``-C'' in perlrun for details.
:locale sub-pragmaStarting in v5.8.6, the encoding name may be :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 chr and ord use that encoding.
The logic of finding which locale :locale uses is as follows:
langinfo(CODESET) interface, the codeset
returned is used as the default encoding for the open pragma.
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 ``.'', if any), and if any found, that is used
as the default encoding for the open pragma.
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, :utf8 is used as the default encoding for the open
pragma.
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
any subsequent file open, is UTF-8.
encoding pragma is in scope then the lengths returned are
calculated from the length of $/ in Unicode characters, which is not
always the same as the length of $/ in the native encoding.
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 ISO 8859-1 (Latin-1).
The encoding pragma changes this to use the specified encoding instead. For example:
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));
Will print 2, because $string is upgraded as UTF-8. Without
use encoding 'utf8';, it will print 4 instead, since $string
is three octets when interpreted as Latin-1.
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 encoding. In other words, this will match in ``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 the same string.
This pragma also affects encoding of the 0x80..0xFF code point range:
normally characters in that range are left as eight-bit bytes (unless
they are combined with characters with code points 0x100 or larger,
in which case all characters need to become UTF-8 encoded), but if
the encoding pragma is present, even the 0x80..0xFF range always
gets 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 a native encoding. So feel free to put your strings in your encoding in quotes and regexes.
The pragma was a per script, not a per block lexical. Only the last
use encoding or no encoding mattered, and it affected
the whole script. However, the no encoding pragma was supported and
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 chr, ord, 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";
STDIN and STDOUT were not set under the filter option.
And STDIN=>ENCODING and STDOUT=>ENCODING didn't work like
non-filter version.
use utf8 wasn't implicitly declared so you have to use utf8 to do
${"\x{4eba}"}++
'\' (BACKSLASH;
\x5c) in the second byte fail because the second byte may
accidentally escape the quoting character that follows.
tr///q//,qq//,qr//,qw///, qx// and so forth. In perl v5.8.0, this
does not apply to tr///. Therefore,
use encoding 'euc-jp'; #.... $kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/; # -------- -------- -------- --------
Does not work as
$kana =~ tr/\x{3041}-\x{3093}/\x{30a1}-\x{30f3}/;
utf8 euc-jp charnames::viacode()
-----------------------------------------
\x{3041} \xA4\xA1 HIRAGANA LETTER SMALL A
\x{3093} \xA4\xF3 HIRAGANA LETTER N
\x{30a1} \xA5\xA1 KATAKANA LETTER SMALL A
\x{30f3} \xA5\xF3 KATAKANA LETTER N
This counterintuitive behavior has been fixed in perl v5.8.1.
In perl v5.8.0, you can work around this as follows;
use encoding 'euc-jp';
# ....
eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ };
Note the tr// expression is surrounded by qq{}. The idea behind
this is the same as the classic idiom that makes tr/// 'interpolate':
tr/$from/$to/; # wrong!
eval qq{ tr/$from/$to/ }; # workaround.
use encoding "iso 8859-7";
# \xDF in ISO 8859-7 (Greek) is \x{3af} in Unicode.
$a = "\xDF";
$b = "\x{100}";
printf "%#x\n", ord($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 ord(chr(0xdf)) == 0x3af;
# ... ord() is affected by the encoding pragma ...
print "tera\n" if ord(pack("C", 0xdf)) == 0x3af;
# ... as are eq and cmp ...
print "peta\n" if "\x{3af}" eq pack("C", 0xdf);
print "exa\n" if "\x{3af}" cmp pack("C", 0xdf) == 0;
# ... but pack/unpack C are not affected, in case you still
# want to go back to your native encoding
print "zetta\n" if unpack("C", (pack("C", 0xdf))) == 0xdf;
use encoding ... is not thread-safe (i.e., do not use in threaded
applications).
STDIN and STDOUT get the encoded streamformatformat because PerlIO does not
get along very well with it. When format contains non-ASCII
characters it prints funny or gets ``wide character warnings''.
To understand it, try the code below.
# Save this one in utf8 # replace *non-ascii* with a non-ascii string my $camel; format STDOUT = *non-ascii*@>>>>>>> $camel . $camel = "*non-ascii*"; binmode(STDOUT=>':encoding(utf8)'); # bang! write; # funny print $camel, "\n"; # fine
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
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).
This pragma first appeared in Perl v5.8.0. It has been enhanced in later releases as specified above.
the perlunicode manpage, the Encode manpage, the open manpage, the Filter::Util::Call manpage,
Ch. 15 of Programming Perl (3rd Edition)
by Larry Wall, Tom Christiansen, Jon Orwant;
O'Reilly & Associates; ISBN 0-596-00027-8
| encoding - allows you to write your script in non-ASCII and non-UTF-8 |