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authorgdamore <gdamore@users.noreply.github.com>2024-10-27 18:55:51 +0000
committergdamore <gdamore@users.noreply.github.com>2024-10-27 18:55:51 +0000
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+ <ol class="chapter"><li class="chapter-item expanded affix "><a href="../copyright.html">Copyright</a></li><li class="chapter-item expanded affix "><a href="../dedication.html">Dedication</a></li><li class="chapter-item expanded affix "><a href="../preface.html">Preface</a></li><li class="chapter-item expanded "><a href="../api/index.html"><strong aria-hidden="true">1.</strong> API Reference</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../api/msg.html"><strong aria-hidden="true">1.1.</strong> Messages</a></li><li class="chapter-item expanded "><a href="../api/memory.html"><strong aria-hidden="true">1.2.</strong> Memory</a></li><li class="chapter-item expanded "><a href="../api/time.html"><strong aria-hidden="true">1.3.</strong> Time</a></li><li class="chapter-item expanded "><a href="../api/url.html"><strong aria-hidden="true">1.4.</strong> URLs</a></li><li class="chapter-item expanded "><a href="../api/aio.html"><strong aria-hidden="true">1.5.</strong> Asynchronous I/O</a></li><li class="chapter-item expanded "><a href="../api/synch.html"><strong aria-hidden="true">1.6.</strong> Synchronization</a></li><li class="chapter-item expanded "><a href="../api/thread.html"><strong aria-hidden="true">1.7.</strong> Threads</a></li><li class="chapter-item expanded "><a href="../api/logging.html"><strong aria-hidden="true">1.8.</strong> Logging</a></li><li class="chapter-item expanded "><a href="../api/stats.html"><strong aria-hidden="true">1.9.</strong> Statistics</a></li><li class="chapter-item expanded "><a href="../api/errors.html"><strong aria-hidden="true">1.10.</strong> Errors</a></li><li class="chapter-item expanded "><a href="../api/misc.html"><strong aria-hidden="true">1.11.</strong> Miscellaneous</a></li><li class="chapter-item expanded "><a href="../api/id_map.html"><strong aria-hidden="true">1.12.</strong> ID Map</a></li><li class="chapter-item expanded "><a href="../api/cmd_opts.html" class="active"><strong aria-hidden="true">1.13.</strong> Command Options</a></li></ol></li><li class="chapter-item expanded "><a href="../proto/index.html"><strong aria-hidden="true">2.</strong> Protocols</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../proto/bus.html"><strong aria-hidden="true">2.1.</strong> BUS Protocol</a></li><li class="chapter-item expanded "><a href="../proto/pair.html"><strong aria-hidden="true">2.2.</strong> PAIR Protocol</a></li><li class="chapter-item expanded "><a href="../proto/pub.html"><strong aria-hidden="true">2.3.</strong> PUB Protocol</a></li><li class="chapter-item expanded "><a href="../proto/pull.html"><strong aria-hidden="true">2.4.</strong> PULL Protocol</a></li><li class="chapter-item expanded "><a href="../proto/push.html"><strong aria-hidden="true">2.5.</strong> PUSH Protocol</a></li><li class="chapter-item expanded "><a href="../proto/rep.html"><strong aria-hidden="true">2.6.</strong> REP Protocol</a></li><li class="chapter-item expanded "><a href="../proto/req.html"><strong aria-hidden="true">2.7.</strong> REQ Protocol</a></li><li class="chapter-item expanded "><a href="../proto/respondent.html"><strong aria-hidden="true">2.8.</strong> RESPONDENT Protocol</a></li><li class="chapter-item expanded "><a href="../proto/sub.html"><strong aria-hidden="true">2.9.</strong> SUB Protocol</a></li><li class="chapter-item expanded "><a href="../proto/surveyor.html"><strong aria-hidden="true">2.10.</strong> SURVEYOR Protocol</a></li></ol></li><li class="chapter-item expanded "><a href="../tran/index.html"><strong aria-hidden="true">3.</strong> Transports</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../tran/inproc.html"><strong aria-hidden="true">3.1.</strong> Intra-Process Transport</a></li><li class="chapter-item expanded "><a href="../tran/ipc.html"><strong aria-hidden="true">3.2.</strong> Inter-Process Transport</a></li><li class="chapter-item expanded "><a href="../tran/socket.html"><strong aria-hidden="true">3.3.</strong> BSD Socket (Experimental)</a></li><li class="chapter-item expanded "><a href="../tran/udp.html"><strong aria-hidden="true">3.4.</strong> UDP Transport (Experimental)</a></li></ol></li><li class="chapter-item expanded "><a href="../migrate/index.html"><strong aria-hidden="true">4.</strong> Migration Guides</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../migrate/nng1.html"><strong aria-hidden="true">4.1.</strong> Migrating from NNG 1.x</a></li><li class="chapter-item expanded "><a href="../migrate/nanomsg.html"><strong aria-hidden="true">4.2.</strong> Migrating from libnanomsg</a></li></ol></li><li class="chapter-item expanded "><a href="../indexing.html">Index</a></li></ol>
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+
+</style>
+<h1 id="command-options"><a class="header" href="#command-options">Command Options</a></h1>
+<p>Some <em>NNG</em> utilities need to parse command line options,
+and the supplementary function here allows applications that
+need the same support to benefit from this.</p>
+<p>To make use of this, the supplemental header <code>&lt;nng/supplemental/util/options.h&gt;</code>
+must be included.</p>
+<h2 id="parse-command-line-options"><a class="header" href="#parse-command-line-options">Parse Command Line Options</a></h2>
+<pre><code class="language-c">typedef struct nng_optspec {
+ const char *o_name; // Long style name (may be NULL for short only)
+ int o_short; // Short option (no clustering!)
+ int o_val; // Value stored on a good parse (&gt;0)
+ bool o_arg; // Option takes an argument if true
+} nng_optspec;
+
+int nng_opts_parse(int argc, char *const *argv,
+ const nng_optspec *spec, int *val, char **arg, int *idx);
+</code></pre>
+<p>The <a name="a001"></a><code>nng_opts_parse</code> function is a intended to facilitate parsing
+<a name="a002"></a>command-line arguments.
+This function exists largely to stand in for <a name="a003"></a><code>getopt</code> from POSIX systems,
+but it is available everywhere that <em>NNG</em> is, and it includes
+some capabilities missing from <code>getopt</code>.</p>
+<p>The function parses arguments from
+<code>main</code><sup><a name="to-footnote-1"><a href="#footnote-1">1</a></a></sup>
+(using <em>argc</em> and <em>argv</em>),
+starting at the index referenced by <em>idx</em>.
+(New invocations typically set the value pointed to by <em>idx</em> to 1.)</p>
+<p>Options are parsed as specified by <em>spec</em> (see <a href="#option-specification">Option Specification</a>.)
+The value of the parsed option will be stored at the address indicated by
+<em>val</em>, and the value of <em>idx</em> will be incremented to reflect the next
+option to parse.</p>
+<div class="mdbook-alerts mdbook-alerts-tip">
+<p class="mdbook-alerts-title">
+ <span class="mdbook-alerts-icon"></span>
+ tip
+</p>
+<p>For using this to parse command-line like strings that do not include
+the command name itself, set the value referenced by <em>idx</em> to zero instead of one.</p>
+</div>
+<p>If the option had an argument, a pointer to that is returned at the address
+referenced by <em>arg</em>.</p>
+<p>This function should be called repeatedly, until it returns either -1
+(indicating the end of options is reached) or a non-zero error code is
+returned.</p>
+<p>This function may return the following errors:</p>
+<ul>
+<li><a href="/api/errors.html#NNG_EAMBIGUOUS"><code>NNG_EAMBIGUOUS</code></a>: Parsed option matches more than one specification.</li>
+<li><a href="/api/errors.html#NNG_ENOARG"><code>NNG_ENOARG</code></a>: Option requires an argument, but one is not present.</li>
+<li><a href="/api/errors.html#NNG_EINVAL"><code>NNG_EINVAL</code></a>: An invalid (unknown) argument is present.</li>
+</ul>
+<h3 id="option-specification"><a class="header" href="#option-specification">Option Specification</a></h3>
+<p>The calling program must first create an array of <a name="a004"></a><code>nng_optspec</code> structures
+describing the options to be supported.
+This structure has the following members:</p>
+<ul>
+<li>
+<p><code>o_name</code>:</p>
+<p>The long style name for the option, such as “verbose”.
+This will be parsed as a <a href="#long-options">long option</a> on the command line when it is prefixed with two dashes.
+It may be <code>NULL</code> if only a <a href="#short-options">short option</a> is to be supported.</p>
+</li>
+<li>
+<p><code>o_short</code>:</p>
+<p>This is a single letter (at present only ASCII letters are supported).
+These options appear as just a single letter, and are prefixed with a single dash on the command line.
+The use of a slash in lieu of the dash is <em>not</em> supported, in order to avoid confusion with path name arguments.
+This value may be set to 0 if no <a href="#short-options">short option</a> is needed.</p>
+</li>
+<li>
+<p><code>o_val</code>:</p>
+<p>This is a numeric value that is unique to this option.
+This value is assigned by the application program, and must be non-zero for a valid option.
+If this is zero, then it indicates the end of the specifications, and the
+rest of this structure is ignored.
+The value will be returned to the caller in <em>val</em> by <code>nng_opts_parse</code> when
+this option is parsed from the command line.</p>
+</li>
+<li>
+<p><code>o_arg</code>:</p>
+<p>This value should be set to <code>true</code> if the option should take an argument.</p>
+</li>
+</ul>
+<h3 id="long-options"><a class="header" href="#long-options">Long Options</a></h3>
+<p>Long options are parsed from the <em>argv</em> array, and are indicated when
+the element being scanned starts with two dashes.
+For example, the “verbose” option would be specified as <code>--verbose</code> on
+the command line.
+If a long option takes an argument, it can either immediately follow
+the option as the next element in <em>argv</em>, or it can be appended to
+the option, separated from the option by an equals sign (<code>=</code>) or a
+colon (<code>:</code>).</p>
+<h3 id="short-options"><a class="header" href="#short-options">Short Options</a></h3>
+<p>Short options appear by themselves in an <em>argv</em> element, prefixed by a dash (<code>-</code>).
+If the short option takes an argument, it can either be appended in the
+same element of <em>argv</em>, or may appear in the next <em>argv</em> element.</p>
+<div class="mdbook-alerts mdbook-alerts-note">
+<p class="mdbook-alerts-title">
+ <span class="mdbook-alerts-icon"></span>
+ note
+</p>
+<p>Option clustering, where multiple options can be crammed together in
+a single <em>argv</em> element, is not supported by this function (yet).</p>
+</div>
+<h3 id="prefix-matching"><a class="header" href="#prefix-matching">Prefix Matching</a></h3>
+<p>When using long options, the parser will match if it is equal to a prefix
+of the <code>o_name</code> member of a option specification, provided that it do so
+unambiguously (meaning it must not match any other option specification.)</p>
+<h2 id="example"><a class="header" href="#example">Example</a></h2>
+<p>The following program fragment demonstrates this function.</p>
+<pre><code class="language-c"> enum { OPT_LOGFILE, OPT_VERBOSE };
+ char *logfile; // options to be set
+ bool verbose;
+
+ static nng_optspec specs[] = {
+ {
+ .o_name = "logfile",
+ .o_short = 'D',
+ .o_val = OPT_LOGFILE,
+ .o_arg = true,
+ }, {
+ .o_name = "verbose",
+ .o_short = 'V',
+ .o_val = OPT_VERBOSE,
+ .o_arg = false,
+ }, {
+ .o_val = 0; // Terminate array
+ }
+ };
+
+ for (int idx = 1;;) {
+ int rv, opt;
+ char *arg;
+ rv = nng_opts_parse(argc, argv, specs, &amp;opt, &amp;arg, &amp;idx);
+ if (rv != 0) {
+ break;
+ }
+ switch (opt) {
+ case OPT_LOGFILE:
+ logfile = arg;
+ break;
+ case OPT_VERBOSE:
+ verbose = true;
+ break;
+ }
+ }
+ if (rv != -1) {
+ printf("Options error: %s\n", nng_strerror(rv));
+ exit(1);
+ }
+</code></pre>
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+<p><a name="footnote-1"><a href="#to-footnote-1">1</a></a>: Parsing argument strings from other sources can be done as well,
+although usually then <em>idx</em> will be initialized to zero.</p>
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