Manpages - encoding.3perl

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 perluniintro and utf8 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 Filter::Encoding 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] ;”

Please note: This mode of operation is no longer supported as of Perl v5.26. 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;”

This operates as above, but the 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;”

Unsets the script encoding. The layers of STDIN, STDOUT are reset to “:raw” (the default unprocessed raw stream of bytes).

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;

Thread safety

use encoding ... is not thread-safe (i.e., do not use in threaded applications).

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.

(no term)

Other modules using “STDIN” and “STDOUT” get the encoded stream :: They may be expecting something completely different.

literals in regex 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 pragma is not supported on EBCDIC platforms.

“format”

This pragma doesn’t work well with format 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).

See also “CAVEATS”

This pragma first appeared in Perl v5.8.0. It has been enhanced in later releases as specified above.

perlunicode, Encode, open, Filter::Util::Call,

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