bytes(3pm) Perl Programmers Reference Guide bytes(3pm)
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 per-luniintro perluniintro
luniintro and perlunicode.
LIMITATIONS
bytes::substr() does not work as an lvalue().
SEE ALSO
perluniintro, perlunicode, utf8
perl v5.8.8 2001-09-21 bytes(3pm)
|