bytes(3) - phpMan

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       superseded.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 v5.16.3                                2013-02-26                                 bytes(3pm)

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