1bytes(3pm) Perl Programmers Reference Guide bytes(3pm)
2
6 bytes - Perl pragma to force byte semantics rather than character
7 semantics
8
10 use bytes;
11 ... chr(...); # or bytes::chr
12 ... index(...); # or bytes::index
13 ... length(...); # or bytes::length
14 ... ord(...); # or bytes::ord
15 ... rindex(...); # or bytes::rindex
16 ... substr(...); # or bytes::substr
17 no bytes;
18
20 The "use bytes" pragma disables character semantics for the rest of the
21 lexical scope in which it appears. "no bytes" can be used to reverse
22 the effect of "use bytes" within the current lexical scope.
23 Perl normally assumes character semantics in the presence of character
25 data (i.e. data that has come from a source that has been marked as
26 being of a particular character encoding). When "use bytes" is in
27 effect, the encoding is temporarily ignored, and each string is treated
28 as a series of bytes.
29 As an example, when Perl sees "$x = chr(400)", it encodes the character
31 in UTF-8 and stores it in $x. Then it is marked as character data, so,
32 for instance, "length $x" returns 1. However, in the scope of the
33 "bytes" pragma, $x is treated as a series of bytes - the bytes that
34 make up the UTF8 encoding - and "length $x" returns 2:
35 $x = chr(400);
37 print "Length is ", length $x, "\n"; # "Length is 1"
38 printf "Contents are %vd\n", $x; # "Contents are 400"
39 {
40 use bytes; # or "require bytes; bytes::length()"
41 print "Length is ", length $x, "\n"; # "Length is 2"
42 printf "Contents are %vd\n", $x; # "Contents are 198.144"
43 }
44 chr(), ord(), substr(), index() and rindex() behave similarly.
46 For more on the implications and differences between character
48 semantics and byte semantics, see perluniintro and perlunicode.
49
51 bytes::substr() does not work as an lvalue().
52
54 perluniintro, perlunicode, utf8
55perl v5.10.1 2009-02-12 bytes(3pm)