bytes(3p) Perl Programmers Reference Guide bytes(3p)
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 encod-
ing). When "use bytes" is in effect, the encoding is tem-
porarily 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 simi-
larly.
For more on the implications and differences between charac-
ter semantics and byte semantics, see perluniintro and per-
lunicode.
bytes::substr() does not work as an lvalue().
perl v5.8.8 2005-02-05 1
bytes(3p) Perl Programmers Reference Guide bytes(3p)
perluniintro, perlunicode, utf8
perl v5.8.8 2005-02-05 2