mingw/html/lib/bytes.html

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   5 <title>bytes - Perl pragma to force byte semantics rather than character semantics</title>
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  13 <big><strong><span class="block">&nbsp;bytes - Perl pragma to force byte semantics rather than character semantics</span></strong></big>
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  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#limitations">LIMITATIONS</a></li>
  26         <li><a href="#see_also">SEE ALSO</a></li>
  27 </ul>
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  29
  30 <hr />
  31 <p>
  32 </p>
  33 <h1><a name="name">NAME</a></h1>
  34 <p>bytes - Perl pragma to force byte semantics rather than character semantics</p>
  35 <p>
  36 </p>
  37 <hr />
  38 <h1><a name="synopsis">SYNOPSIS</a></h1>
  39 <pre>
  40     use bytes;
  41     ... chr(...);       # or bytes::chr
  42     ... index(...);     # or bytes::index
  43     ... length(...);    # or bytes::length
  44     ... ord(...);       # or bytes::ord
  45     ... rindex(...);    # or bytes::rindex
  46     ... substr(...);    # or bytes::substr
  47     no bytes;</pre>
  48 <p>
  49 </p>
  50 <hr />
  51 <h1><a name="description">DESCRIPTION</a></h1>
  52 <p>The <code>use bytes</code> pragma disables character semantics for the rest of the
  53 lexical scope in which it appears.  <code>no bytes</code> can be used to reverse
  54 the effect of <code>use bytes</code> within the current lexical scope.</p>
  55 <p>Perl normally assumes character semantics in the presence of character
  56 data (i.e. data that has come from a source that has been marked as
  57 being of a particular character encoding). When <code>use bytes</code> is in
  58 effect, the encoding is temporarily ignored, and each string is treated
  59 as a series of bytes.</p>
  60 <p>As an example, when Perl sees <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_chr"><code>$x = chr(400)</code></a>, it encodes the character
  61 in UTF-8 and stores it in $x. Then it is marked as character data, so,
  62 for instance, <code>length $x</code> returns <code>1</code>. However, in the scope of the
  63 <code>bytes</code> pragma, $x is treated as a series of bytes - the bytes that make
  64 up the UTF8 encoding - and <code>length $x</code> returns <code>2</code>:</p>
  65 <pre>
  66     $x = chr(400);
  67     print &quot;Length is &quot;, length $x, &quot;\n&quot;;     # &quot;Length is 1&quot;
  68     printf &quot;Contents are %vd\n&quot;, $x;         # &quot;Contents are 400&quot;
  69     {
  70         use bytes; # or &quot;require bytes; bytes::length()&quot;
  71         print &quot;Length is &quot;, length $x, &quot;\n&quot;; # &quot;Length is 2&quot;
  72         printf &quot;Contents are %vd\n&quot;, $x;     # &quot;Contents are 198.144&quot;
  73     }</pre>
  74 <p>chr(), ord(), substr(), <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_index"><code>index()</code></a> and <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_rindex"><code>rindex()</code></a> behave similarly.</p>
  75 <p>For more on the implications and differences between character
  76 semantics and byte semantics, see <a href="file://C|\msysgit\mingw\html/pod/perluniintro.html">the perluniintro manpage</a> and <a href="file://C|\msysgit\mingw\html/pod/perlunicode.html">the perlunicode manpage</a>.</p>
  77 <p>
  78 </p>
  79 <hr />
  80 <h1><a name="limitations">LIMITATIONS</a></h1>
  81 <p>bytes::substr() does not work as an lvalue().</p>
  82 <p>
  83 </p>
  84 <hr />
  85 <h1><a name="see_also">SEE ALSO</a></h1>
  86 <p><a href="file://C|\msysgit\mingw\html/pod/perluniintro.html">the perluniintro manpage</a>, <a href="file://C|\msysgit\mingw\html/pod/perlunicode.html">the perlunicode manpage</a>, <a href="file://C|\msysgit\mingw\html/lib/utf8.html">the utf8 manpage</a></p>
  87 <table border="0" width="100%" cellspacing="0" cellpadding="3">
  88 <tr><td class="block" style="background-color: #cccccc" valign="middle">
  89 <big><strong><span class="block">&nbsp;bytes - Perl pragma to force byte semantics rather than character semantics</span></strong></big>
  90 </td></tr>
  91 </table>
  92
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