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bytes(3pm)             Perl Programmers Reference Guide             bytes(3pm)

NAME
       bytes - Perl pragma to force byte semantics rather than character
       semantics

NOTICE
       This pragma reflects early attempts to incorporate Unicode into perl
       and has since been superseded. It breaks encapsulation (i.e. it exposes
       the innards of how the perl executable currently happens to store a
       string), and use of this module for anything other than debugging
       purposes is strongly discouraged. If you feel that the functions here
       within might be useful for your application, this possibly indicates a
       mismatch between your mental model of Perl Unicode and the current
       reality. In that case, you may wish to read some of the perl Unicode
       documentation: perluniintro, perlunitut, perlunifaq and perlunicode.

SYNOPSIS
           use bytes;
           ... chr(...);       # or bytes::chr
           ... index(...);     # or bytes::index
           ... length(...);    # or bytes::length
           ... ord(...);       # or bytes::ord
           ... rindex(...);    # or bytes::rindex
           ... substr(...);    # or bytes::substr
           no bytes;

DESCRIPTION
       The "use bytes" pragma disables character semantics for the rest of the
       lexical scope in which it appears.  "no bytes" can be used to reverse
       the effect of "use bytes" within the current lexical scope.

       Perl normally assumes character semantics in the presence of character
       data (i.e. data that has come from a source that has been marked as
       being of a particular character encoding). When "use bytes" is in
       effect, the encoding is temporarily ignored, and each string is treated
       as a series of bytes.

       As an example, when Perl sees "$x = chr(400)", it encodes the character
       in UTF-8 and stores it in $x. Then it is marked as character data, so,
       for instance, "length $x" returns 1. However, in the scope of the
       "bytes" pragma, $x is treated as a series of bytes - the bytes that
       make up the UTF8 encoding - and "length $x" returns 2:

           $x = chr(400);
           print "Length is ", length $x, "\n";     # "Length is 1"
           printf "Contents are %vd\n", $x;         # "Contents are 400"
           {
               use bytes; # or "require bytes; bytes::length()"
               print "Length is ", length $x, "\n"; # "Length is 2"
               printf "Contents are %vd\n", $x;     # "Contents are 198.144"
           }

       chr(), ord(), substr(), index() and rindex() behave similarly.

       For more on the implications and differences between character
       semantics and byte semantics, see perluniintro and perlunicode.

LIMITATIONS
       bytes::substr() does not work as an lvalue().

SEE ALSO
       perluniintro, perlunicode, utf8

perl v5.12.1                      2010-04-26                        bytes(3pm)
 

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Gedruckt am: 11.12.2017 23:32 GMT+0100 (2017-12-11T23:32:48+01:00)