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bytes - Perl pragma to force byte semantics rather than character semantics
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;
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 the perluniintro manpage and the perlunicode manpage.
bytes::substr() does not work as an lvalue().
the perluniintro manpage, the perlunicode manpage, the utf8 manpage