Rafaël Garcia-Suarez > perl-5.9.3 > utf8

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Module Version: 1.06   Source   Latest Release: perl-5.21.1

NAME ^

utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code

SYNOPSIS ^

    use utf8;
    no utf8;

    # Convert a Perl scalar to/from UTF-8.
    $num_octets = utf8::upgrade($string);
    $success    = utf8::downgrade($string[, FAIL_OK]);

    # Change the native bytes of a Perl scalar to/from UTF-8 bytes.
    utf8::encode($string);
    utf8::decode($string);

    $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
    $flag = utf8::valid(STRING);

DESCRIPTION ^

The use utf8 pragma tells the Perl parser to allow UTF-8 in the program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based platforms). The no utf8 pragma tells Perl to switch back to treating the source text as literal bytes in the current lexical scope.

This pragma is primarily a compatibility device. Perl versions earlier than 5.6 allowed arbitrary bytes in source code, whereas in future we would like to standardize on the UTF-8 encoding for source text.

Do not use this pragma for anything else than telling Perl that your script is written in UTF-8. The utility functions described below are useful for their own purposes, but they are not really part of the "pragmatic" effect.

Until UTF-8 becomes the default format for source text, either this pragma or the encoding pragma should be used to recognize UTF-8 in the source. When UTF-8 becomes the standard source format, this pragma will effectively become a no-op. For convenience in what follows the term UTF-X is used to refer to UTF-8 on ASCII and ISO Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.

See also the effects of the -C switch and its cousin, the $ENV{PERL_UNICODE}, in perlrun.

Enabling the utf8 pragma has the following effect:

Note that if you have bytes with the eighth bit on in your script (for example embedded Latin-1 in your string literals), use utf8 will be unhappy since the bytes are most probably not well-formed UTF-8. If you want to have such bytes and use utf8, you can disable utf8 until the end the block (or file, if at top level) by no utf8;.

If you want to automatically upgrade your 8-bit legacy bytes to UTF-8, use the encoding pragma instead of this pragma. For example, if you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to UTF-8 as used in e.g. chr() and \x{...}, try this:

    use encoding "latin-1";
    my $c = chr(0xc4);
    my $x = "\x{c5}";

In case you are wondering: yes, use encoding 'utf8'; works much the same as use utf8;.

Utility functions

The following functions are defined in the utf8:: package by the Perl core. You do not need to say use utf8 to use these and in fact you should not say that unless you really want to have UTF-8 source code.

utf8::encode is like utf8::upgrade, but the UTF8 flag is cleared. See perlunicode for more on the UTF8 flag and the C API functions sv_utf8_upgrade, sv_utf8_downgrade, sv_utf8_encode, and sv_utf8_decode, which are wrapped by the Perl functions utf8::upgrade, utf8::downgrade, utf8::encode and utf8::decode. Note that in the Perl 5.8.0 and 5.8.1 implementation the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode, utf8::upgrade, and utf8::downgrade are always available, without a require utf8 statement-- this may change in future releases.

BUGS ^

One can have Unicode in identifier names, but not in package/class or subroutine names. While some limited functionality towards this does exist as of Perl 5.8.0, that is more accidental than designed; use of Unicode for the said purposes is unsupported.

One reason of this unfinishedness is its (currently) inherent unportability: since both package names and subroutine names may need to be mapped to file and directory names, the Unicode capability of the filesystem becomes important-- and there unfortunately aren't portable answers.

SEE ALSO ^

perluniintro, encoding, perlrun, bytes, perlunicode

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