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<title>getsubopt</title>
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<basefont size="3"> <a name="getsubopt"></a> <a name="tag_03_253"></a><!-- getsubopt -->
<!--header start-->
<center><font size="2">The Open Group Base Specifications Issue 6<br>
IEEE Std 1003.1-2001<br>
Copyright &copy; 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
<!--header end-->
<hr size="2" noshade>
<h4><a name="tag_03_253_01"></a>NAME</h4>
<blockquote>getsubopt - parse suboption arguments from a string</blockquote>
<h4><a name="tag_03_253_02"></a>SYNOPSIS</h4>
<blockquote class="synopsis">
<div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt=
"[Option Start]" border="0"> #include &lt;<a href="../basedefs/stdlib.h.html">stdlib.h</a>&gt;<br>
<br>
int getsubopt(char **</tt><i>optionp</i><tt>, char * const *</tt><i>tokens</i><tt>, char **</tt><i>valuep</i><tt>); <img src=
"../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
<tt><br>
</tt></blockquote>
<h4><a name="tag_03_253_03"></a>DESCRIPTION</h4>
<blockquote>
<p>The <i>getsubopt</i>() function shall parse suboption arguments in a flag argument. Such options often result from the use of <a
href="../functions/getopt.html"><i>getopt</i>()</a>.</p>
<p>The <i>getsubopt</i>() argument <i>optionp</i> is a pointer to a pointer to the option argument string. The suboption arguments
shall be separated by commas and each may consist of either a single token, or a token-value pair separated by an equal sign.</p>
<p>The <i>keylistp</i> argument shall be a pointer to a vector of strings. The end of the vector is identified by a null pointer.
Each entry in the vector is one of the possible tokens that might be found in *<i>optionp</i>. Since commas delimit suboption
arguments in <i>optionp</i>, they should not appear in any of the strings pointed to by <i>keylistp</i>. Similarly, because an
equal sign separates a token from its value, the application should not include an equal sign in any of the strings pointed to by
<i>keylistp</i>.</p>
<p>The <i>valuep</i> argument is the address of a value string pointer.</p>
<p>If a comma appears in <i>optionp</i>, it shall be interpreted as a suboption separator. After commas have been processed, if
there are one or more equal signs in a suboption string, the first equal sign in any suboption string shall be interpreted as a
separator between a token and a value. Subsequent equal signs in a suboption string shall be interpreted as part of the value.</p>
<p>If the string at *<i>optionp</i> contains only one suboption argument (equivalently, no commas), <i>getsubopt</i>() shall update
*<i>optionp</i> to point to the null character at the end of the string. Otherwise, it shall isolate the suboption argument by
replacing the comma separator with a null character, and shall update *<i>optionp</i> to point to the start of the next suboption
argument. If the suboption argument has an associated value (equivalently, contains an equal sign), <i>getsubopt</i>() shall update
*<i>valuep</i> to point to the value's first character. Otherwise, it shall set *<i>valuep</i> to a null pointer. The calling
application may use this information to determine whether the presence or absence of a value for the suboption is an error.</p>
<p>Additionally, when <i>getsubopt</i>() fails to match the suboption argument with a token in the <i>keylistp</i> array, the
calling application should decide if this is an error, or if the unrecognized option should be processed in another way.</p>
</blockquote>
<h4><a name="tag_03_253_04"></a>RETURN VALUE</h4>
<blockquote>
<p>The <i>getsubopt</i>() function shall return the index of the matched token string, or -1 if no token strings were matched.</p>
</blockquote>
<h4><a name="tag_03_253_05"></a>ERRORS</h4>
<blockquote>
<p>No errors are defined.</p>
</blockquote>
<hr>
<div class="box"><em>The following sections are informative.</em></div>
<h4><a name="tag_03_253_06"></a>EXAMPLES</h4>
<blockquote>
<pre>
<tt>#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
<br>
int do_all;
const char *type;
int read_size;
int write_size;
int read_only;
<br>
enum
{
RO_OPTION = 0,
RW_OPTION,
READ_SIZE_OPTION,
WRITE_SIZE_OPTION
};
<br>
const char *mount_opts[] =
{
[RO_OPTION] = "ro",
[RW_OPTION] = "rw",
[READ_SIZE_OPTION] = "rsize",
[WRITE_SIZE_OPTION] = "wsize",
NULL
};
<br>
int
main(int argc, char *argv[])
{
char *subopts, *value;
int opt;
<br>
while ((opt = getopt(argc, argv, "at:o:")) != -1)
switch(opt)
{
case 'a':
do_all = 1;
break;
case 't':
type = optarg;
break;
case 'o':
subopts = optarg;
while (*subopts != '\0')
switch(getsubopt(&amp;subopts, mount_opts, &amp;value))
{
case RO_OPTION:
read_only = 1;
break;
case RW_OPTION:
read_only = 0;
break;
case READ_SIZE_OPTION:
if (value == NULL)
abort();
read_size = atoi(value);
break;
case WRITE_SIZE_OPTION:
if (value == NULL)
abort();
write_size = atoi(value);
break;
default:
/* Unknown suboption. */
printf("Unknown suboption `%s'\n", value);
break;
}
break;
default:
abort();
}
<br>
/* Do the real work. */
<br>
return 0;
}
</tt>
</pre>
<h5><a name="tag_03_253_06_01"></a>Parsing Suboptions</h5>
<p>The following example uses the <i>getsubopt</i>() function to parse a <i>value</i> argument in the <i>optarg</i> external
variable returned by a call to <a href="../functions/getopt.html"><i>getopt</i>()</a>.</p>
<pre>
<tt>#include &lt;stdlib.h&gt;
...
char *tokens[] = {"HOME", "PATH", "LOGNAME", (char *) NULL };
char *value;
int opt, index;
<br>
while ((opt = getopt(argc, argv, "e:")) != -1) {
switch(opt) {
case 'e' :
while ((index = getsubopt(&amp;optarg, tokens, &amp;value)) != -1) {
switch(index) {
...
}
break;
...
}
}
...
</tt>
</pre>
</blockquote>
<h4><a name="tag_03_253_07"></a>APPLICATION USAGE</h4>
<blockquote>
<p>None.</p>
</blockquote>
<h4><a name="tag_03_253_08"></a>RATIONALE</h4>
<blockquote>
<p>None.</p>
</blockquote>
<h4><a name="tag_03_253_09"></a>FUTURE DIRECTIONS</h4>
<blockquote>
<p>None.</p>
</blockquote>
<h4><a name="tag_03_253_10"></a>SEE ALSO</h4>
<blockquote>
<p><a href="getopt.html"><i>getopt</i>()</a> , the Base Definitions volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../basedefs/stdlib.h.html"><i>&lt;stdlib.h&gt;</i></a></p>
</blockquote>
<h4><a name="tag_03_253_11"></a>CHANGE HISTORY</h4>
<blockquote>
<p>First released in Issue 4, Version 2.</p>
</blockquote>
<h4><a name="tag_03_253_12"></a>Issue 5</h4>
<blockquote>
<p>Moved from X/OPEN UNIX extension to BASE.</p>
</blockquote>
<div class="box"><em>End of informative text.</em></div>
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