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| 22 | <title>Pointer Dereference (GNU C Language Manual)</title>
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| 23 |
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| 30 | <link href="Symbol-Index.html" rel="index" title="Symbol Index">
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| 31 | <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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| 32 | <link href="Pointers.html" rel="up" title="Pointers">
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| 33 | <link href="Null-Pointers.html" rel="next" title="Null Pointers">
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| 56 |
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| 57 | <body lang="en">
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| 58 | <span id="Pointer-Dereference"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Null-Pointers.html" accesskey="n" rel="next">Null Pointers</a>, Previous: <a href="Pointer-Type-Designators.html" accesskey="p" rel="prev">Pointer Type Designators</a>, Up: <a href="Pointers.html" accesskey="u" rel="up">Pointers</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Index.html" title="Index" rel="index">Index</a>]</p>
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| 61 | </div>
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| 62 | <hr>
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| 63 | <span id="Dereferencing-Pointers"></span><h3 class="section">14.5 Dereferencing Pointers</h3>
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| 64 | <span id="index-dereferencing-pointers"></span>
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| 65 | <span id="index-pointer-dereferencing"></span>
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| 66 |
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| 67 | <p>The main use of a pointer value is to <em>dereference it</em> (access the
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| 68 | data it points at) with the unary ‘<samp>*</samp>’ operator. For instance,
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| 69 | <code>*&i</code> is the value at <code>i</code>’s address—which is just
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| 70 | <code>i</code>. The two expressions are equivalent, provided <code>&i</code> is
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| 71 | valid.
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| 72 | </p>
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| 73 | <p>A pointer-dereference expression whose type is data (not a function)
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| 74 | is an lvalue.
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| 75 | </p>
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| 76 | <p>Pointers become really useful when we store them somewhere and use
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| 77 | them later. Here’s a simple example to illustrate the practice:
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| 78 | </p>
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| 79 | <div class="example">
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| 80 | <pre class="example">{
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| 81 | int i;
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| 82 | int *ptr;
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| 83 |
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| 84 | ptr = &i;
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| 85 |
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| 86 | i = 5;
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| 87 |
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| 88 | <span class="roman">…</span>
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| 89 |
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| 90 | return *ptr; /* <span class="roman">Returns 5, fetched from <code>i</code>.</span> */
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| 91 | }
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| 92 | </pre></div>
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| 93 |
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| 94 | <p>This shows how to declare the variable <code>ptr</code> as type
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| 95 | <code>int *</code> (pointer to <code>int</code>), store a pointer value into it
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| 96 | (pointing at <code>i</code>), and use it later to get the value of the
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| 97 | object it points at (the value in <code>i</code>).
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| 98 | </p>
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| 99 | <p>If anyone can provide a useful example which is this basic,
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| 100 | I would be grateful.
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| 101 | </p>
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| 102 |
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| 103 |
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| 104 |
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| 105 | </body>
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| 106 | </html>
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