


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


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

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().





perl v5.10.1                2008-09-29                          1





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


SEE ALSO
       perluniintro, perlunicode, utf8























































perl v5.10.1                2008-09-29                          2


