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| 57 | <body lang="en">
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| 58 | <span id="while-Statement"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="do_002dwhile-Statement.html" accesskey="n" rel="next">do-while Statement</a>, Up: <a href="Loop-Statements.html" accesskey="u" rel="up">Loop Statements</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="while-Statement-1"></span><h4 class="subsection">19.6.1 <code>while</code> Statement</h4>
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| 64 | <span id="index-while-statement"></span>
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| 65 | <span id="index-statement_002c-while"></span>
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| 66 | <span id="index-while"></span>
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| 67 |
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| 68 | <p>The <code>while</code> statement is the simplest loop construct.
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| 69 | It looks like this:
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| 70 | </p>
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| 71 | <div class="example">
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| 72 | <pre class="example">while (<var>test</var>)
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| 73 | <var>body</var>
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| 74 | </pre></div>
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| 75 |
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| 76 | <p>Here, <var>body</var> is a statement (often a nested block) to repeat, and
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| 77 | <var>test</var> is the test expression that controls whether to repeat it again.
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| 78 | Each iteration of the loop starts by computing <var>test</var> and, if it
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| 79 | is true (nonzero), that means the loop should execute <var>body</var> again
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| 80 | and then start over.
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| 81 | </p>
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| 82 | <p>Here’s an example of advancing to the last structure in a chain of
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| 83 | structures chained through the <code>next</code> field:
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| 84 | </p>
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| 85 | <div class="example">
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| 86 | <pre class="example">#include <stddef.h> /* <span class="roman">Defines <code>NULL</code>.</span> */
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| 87 | <span class="roman">…</span>
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| 88 | while (chain->next != NULL)
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| 89 | chain = chain->next;
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| 90 | </pre></div>
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| 91 |
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| 92 | <p>This code assumes the chain isn’t empty to start with; if the chain is
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| 93 | empty (that is, if <code>chain</code> is a null pointer), the code gets a
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| 94 | <code>SIGSEGV</code> signal trying to dereference that null pointer (see <a href="Signals.html">Signals</a>).
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| 95 | </p>
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| 96 |
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| 97 |
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| 98 |
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| 99 | </body>
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