209 lines
5.3 KiB
HTML
209 lines
5.3 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>getopt()--Get Flag Letters from Argument Vector</title>
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<!-- Begin Header Records ========================================== -->
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Change History: -->
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<!-- UNIX11 SCRIPT A converted by B2H R4.1 (346) (CMS) by V2DCIJB at -->
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<!-- RCHVMW2 on 1 Jun 1999 at 16:14:12 -->
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<!-- Edited by Kersten Feb 02 -->
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<!-- This file has undergone html cleanup July 2002 by JET -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!--End Header Records -->
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<!-- Java sync-link -->
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>getopt()--Get Flag Letters from Argument Vector</h2>
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<div class="box" style="width: 70%;">
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<br>
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Syntax<br>
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<pre>
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#include <unistd.h>
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int getopt(int <em>argc</em>, char * const <em>argv</em>[],
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const char *<em>optionstring</em>);
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</pre>
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<br>
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Service Program Name: QP0ZCPA<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: No<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>getopt()</strong> function returns the next flag letter in the
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<em>argv</em> list that matches a letter in <em>optionstring</em>. The
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<em>optarg</em> external variable is set to point to the start of the flag's
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parameter on return from <strong>getopt()</strong></p>
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<p><strong>getopt()</strong> places the <em>argv</em> index of the next
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argument to be processed in <em>optind</em>. The <em>optind</em> variable
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is external. It is initialized to 1 before the first call to
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<strong>getopt()</strong>.</p>
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<p><strong>getopt()</strong> can be used to help a program interpret command
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line flags that are passed to it.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong><em>argc</em></strong></dt>
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<dd>(Input) The number of parameters passed by the function.<br>
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<br>
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</dd>
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<dt><strong><em>argv</em></strong></dt>
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<dd>(Input) The list of parameters passed to the function.<br>
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<br>
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</dd>
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<dt><strong><em>optionstring</em></strong></dt>
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<dd>(Input) A string of flag letters. The string must contain the flag letters
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that the program using <strong>getopt()</strong> recognizes. If a letter is
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followed by a colon, the flag is expected to have an argument or group of
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arguments, which can be separated from it by blank spaces.
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<p>The special flag "--" (two hyphens) can be used to delimit the end of the
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options. When this flag is encountered, the "--" is skipped and EOF is
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returned. This flag is useful in delimiting arguments beginning with a hyphen
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that are not options.</p>
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</dd>
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</dl>
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<br>
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<h3>Authorities</h3>
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<p>None.</p>
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<br>
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<h3>Return Value</h3>
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<table cellpadding="5">
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<!-- cols="5 95" -->
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<tr>
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<td align="left" valign="top">EOF</td>
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<td align="left" valign="top"><strong>getopt()</strong> processed all flags
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(that is, up to the first argument that is not a flag).</td>
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</tr>
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<tr>
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<td align="left" valign="top">'?'</td>
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<td align="left" valign="top"><strong>getopt()</strong> encountered a flag
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letter that was not included in <em>optionstring</em>. The variable
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<em>optopt</em> is set to the real option found in <em>argv</em> regardless
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of whether the flag is in <em>optionstring</em> of not. An error message is
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printed to <samp>stderr</samp>. The generation of error messages can be suppressed
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by setting <em>opterr</em> to 0.</td>
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</tr>
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</table>
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<br>
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<br>
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<h3>Error Conditions</h3>
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<p>The <strong>getopt()</strong> function does not return an error.</p>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<p>The following example processes the flags for a command that can take the
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mutually exclusive flags a and b, and the flags f and o, both of which require
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parameters.</p>
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<pre>
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#include <unistd.h>
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int main( int argc, char *argv[] )
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{
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int c;
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extern int optind;
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extern char *optarg;
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.
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.
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.
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while ((c = getopt(argc, argv, "abf:o:")) != EOF)
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{
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switch (c)
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{
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case 'a':
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if (bflg)
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errflg++;
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else
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aflg++;
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break;
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case 'b':
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if (aflg)
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errflg++;
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else
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bflg++;
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break;
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case 'f':
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ifile = optarg;
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break;
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case 'o':
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ofile = optarg;
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break;
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case '?':
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errflg++;
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} /* case */
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if (errflg)
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{
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fprintf(stderr, "usage: . . . ");
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exit(2);
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}
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} /* while */
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for ( ; optind < argc; optind++)
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{
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if (access(argv[optind], R_OK))
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{
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.
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.
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.
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}
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} /* for */
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} /* main */
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</pre>
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<br>
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<hr>
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API introduced: V3R6
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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