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| 22 | <title>Command-line Parameters (GNU C Language Manual)</title>
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| 57 | <body lang="en">
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| 58 | <span id="Command_002dline-Parameters"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Environment-Variables.html" accesskey="n" rel="next">Environment Variables</a>, Previous: <a href="Values-from-main.html" accesskey="p" rel="prev">Values from main</a>, Up: <a href="The-main-Function.html" accesskey="u" rel="up">The main Function</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="Accessing-Command_002dline-Parameters"></span><h4 class="subsection">22.6.2 Accessing Command-line Parameters</h4>
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| 64 | <span id="index-command_002dline-parameters"></span>
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| 65 | <span id="index-parameters_002c-command_002dline"></span>
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| 66 |
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| 67 | <p>If the program was invoked with any command-line arguments, it can
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| 68 | access them through the arguments of <code>main</code>, <code>argc</code> and
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| 69 | <code>argv</code>. (You can give these arguments any names, but the names
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| 70 | <code>argc</code> and <code>argv</code> are customary.)
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| 71 | </p>
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| 72 | <p>The value of <code>argv</code> is an array containing all of the
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| 73 | command-line arguments as strings, with the name of the command
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| 74 | invoked as the first string. <code>argc</code> is an integer that says how
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| 75 | many strings <code>argv</code> contains. Here is an example of accessing
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| 76 | the command-line parameters, retrieving the program’s name and
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| 77 | checking for the standard <samp>--version</samp> and <samp>--help</samp> options:
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| 78 | </p>
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| 79 | <div class="example">
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| 80 | <pre class="example">#include <string.h> /* <span class="roman">Declare <code>strcmp</code>.</span> */
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| 81 |
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| 82 | int
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| 83 | main (int argc, char *argv[])
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| 84 | {
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| 85 | char *program_name = argv[0];
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| 86 |
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| 87 | for (int i = 1; i < argc; i++)
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| 88 | {
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| 89 | if (!strcmp (argv[i], "--version"))
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| 90 | {
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| 91 | /* <span class="roman">Print version information and exit.</span> */
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| 92 | <span class="roman">…</span>
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| 93 | }
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| 94 | else if (!strcmp (argv[i], "--help"))
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| 95 | {
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| 96 | /* <span class="roman">Print help information and exit.</span> */
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| 97 | <span class="roman">…</span>
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| 98 | }
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| 99 | }
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| 100 | <span class="roman">…</span>
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| 101 | }
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| 102 | </pre></div>
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| 103 |
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| 104 |
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| 105 |
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| 106 |
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| 107 | </body>
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| 108 | </html>
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