Document nng_opts_parse.

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diff --git a/docs/man/libnng.3.adoc b/docs/man/libnng.3.adoc
index c5c345f6..2fd0109f 100644
--- a/docs/man/libnng.3.adoc
+++ b/docs/man/libnng.3.adoc
@@ -207,6 +207,17 @@ universal resource locators (URLS).
 |===
 
 
+=== Supplemental API
+
+These supplemental functions are not intrinsic to building
+network applications with _NNG_, but they are made available
+as a convenience to aid in creating portable applications.
+
+|===
+|<<nng_opts_parse.3#,nng_opts_parse()>>|parse command line options
+|===
+
+
 === HTTP Support
 
 The library may be configured with support for HTTP, and this will
diff --git a/docs/man/man3supp.desc b/docs/man/man3supp.desc
new file mode 100644
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@@ -0,0 +1,3 @@
+This section documents supplemental functions that are available.
+These functions are not intrinsic to building applications with
+this library, but their presence may facilitate writing portable applications.
diff --git a/docs/man/man3supp.sect b/docs/man/man3supp.sect
new file mode 100644
index 00000000..7c8e3822
--- /dev/null
+++ b/docs/man/man3supp.sect
@@ -0,0 +1 @@
+Supplemental Functions
diff --git a/docs/man/nng_opts_parse.3supp b/docs/man/nng_opts_parse.3supp
new file mode 100644
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+++ b/docs/man/nng_opts_parse.3supp
@@ -0,0 +1,183 @@
+= nng_opts_parse(3supp)
+//
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+//
+// This document is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+== NAME
+
+nng_opts_parse - parse command line options
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+#include <nng/supplemental/util/options.h>
+
+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 (>0)
+    bool        o_arg;   // Option takes an argument if true        
+} nng_optspec;
+
+int nng_opts_parse(int argc, const char **argv, const nng_optspec *spec, int *val, const char **arg, int *idx);
+----
+
+== DESCRIPTION
+
+The `nng_opts_parse()` is function is a supplemental funtion intened to
+facilitate parsing command line arguments.
+This function exists largely to stand in for `getopt()` from POSIX
+systems, but it is available everywhere that _NNG_ is, and it includes
+some capabilities missing from `getopt()`.
+
+The function parses arguments from `main()` (using _argc_ and _argv_),
+starting at the index referenced by _idx_.
+(New invocations typically set the value pointed to by _idx_ to 1.)
+
+Options are parsed as specified by _spec_ (see <<Option Specification>>.)
+The value of the parsed option will be stored at the address indicated by
+_val_, and the value of _idx_ will be incremented to reflect the next
+option to parse.
+
+TIP: For using this to parse command-line like strings that do not include
+the command name itself, set the value referenced by _idx_ to zero
+instead of one.
+
+If the option had an argument, a pointer to that is returned at the address
+referenced by _arg_.
+
+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.
+
+=== Option Specification
+
+The calling program must first create an array of `nng_optspec` structures
+describing the options to be supported.
+This structure has the following members:
+
+`o_name`::
+
+  The long style name for the option, such as "verbose".
+  This will be parsed on the command line when it is prefixed with two dashes.
+  It may be `NULL` if only a short option is to be supported.
+
+`o_short`::
+
+  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 _not_ supported, in order to avoid confusion with path name arguments.
+  This value may be set to 0 if no short option is needed.
+
+`o_val`::
+
+  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 _val_ by `nng_opts_parse()` when
+  this option is parsed from the command line.
+
+`o_arg`::
+
+  This value should be set to `true` if the option should take an argument.
+
+=== Long Options
+
+Long options are parsed from the _argv_ array, and are indicated when
+the element being scanned starts with two dashes. 
+For example, the "verbose" option would be specified as `--verbose` on
+the command line.
+If a long option takes an argument, it can either immediately follow
+the option as the next element in _argv_, or it can be appended to
+the option, separated from the option by an equals sign (`=`) or a
+colon (`:`).
+
+=== Short Options
+
+Short options appear by themselves in an _argv_ element, prefixed by a
+dash (`-`).
+If the short option takes an argument, it can either be appended in the
+same element of _argv_, or may appear in the next _argv_ element.
+
+NOTE: Option clustering, where multiple options can be crammed together in
+a single _argv_ element, is not supported by this function (yet).
+
+=== Prefix Matching
+
+When using long options, the parser will match if it is equal to a prefix
+of the `o_name` member of a option specification, provided that it do so
+unambiguously (meaning it must not match any other option specification.)
+
+== EXAMPLE
+
+The following program fragment demonstrates this function.
+
+[source, 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, &opt, &arg, &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);
+    }
+----
+
+== RETURN VALUES
+
+This function returns 0 if an option parsed correctly, -1 if
+no more options are available to be parsed, or an error number otherwise.
+
+== ERRORS
+
+`NNG_EAMBIGUOUS`:: Parsed option matches more than one specification.
+`NNG_ENOARG`:: Option requires an argument, but one is not present.
+`NNG_EINVAL`:: An invalid (unknown) argument is present.
+
+== SEE ALSO
+
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng.7#,nng(7)>>