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 .Dd Jan 23, 2017
 .Dt GETHOPT 3
 .Os Mastodon
 .Sh NAME
 .Nm gethopt
 .Nd get option letter or word from argv
 .Sh SYNOPSIS
 .Fd #include "gethopt.h"
 
 .Bd -literal -compact
 struct h_opt {
     int  option;
     char *optword;
     char optchar;
     int  opthasarg;
     char *optdesc;
 } ;
 .Ed
 .Ft char*
 .Fn hoptarg "struct h_context* argctx"
 .Ft int
 .Fn hoptind "struct h_context* argctx"
 .Ft int
 .Fn hopterr "struct h_context* argctx" "int flag"
 .Ft char
 .Fn hoptopt "struct h_context* argctx"
 .Ft void
 .Fn hoptset "struct h_context* argctx" "int argc" "char** argv"
 .Ft struct h_opt*
 .Fn gethopt "struct h_context* argctx" "struct h_opt* optarray" "int nropts"
 
 .Sh DESCRIPTION
 The
 .Fn gethopt
 function gets 
 the next
 .Em known
 option word or character from
 .Fa argctx .
 An option is
 .Em known
 if it has been specified in the array of accepted options
 .Fa optarray .
 .Pp
 The option array
 .Fa optarray
 contains records with either an option word, character, or both,
 a flag saying the option needs an argument, a short description
 of the option, and an
 .Va option
 key (which is there for the convenience of the calling program;
 .Fn gethopt
 does not use it in any way.).
 It does not matter to
 .Fn getopt
 if a following argument has leading white space.
 .Pp
 On return from
 .Fn gethopt ,
 .Fn hoptarg
 returns an option argument, if it is anticipated,
 and the variable
 .Fn hoptind
 contains the index to the next
 .Fa argv
 argument for a subsequent call
 to
 .Fn gethopt .
 .Pp
 .Fn
 gethopt
 uses a (semi) opaque data blob to hold the current state, which
 must be initialized by the
 .Fn hoptset
 function.
 .Pp
 The
 .Fn gethopt
 function
 returns
 .Dv HOPTERR
 if a non-recognized
 option is encountered,
 and NULL when it reaches the end of the options on the command line..
 .Pp
 The interpretation of options in the argument list may be cancelled
 by 
 .Ql -
 (single dash) or
 .Ql --
 (double dash) which causes
 .Fn getopt
 to signal the end of argument processing and return an
 .Dv NULL . 
 When all options have been processed (i.e., up to the first non-option
 argument),
 .Fn gethopt
 returns
 .Dv NULL .
 .Sh DIAGNOSTICS
 If the
 .Fn gethopt
 function encounters a character not found in
 .Va optarray
 or detects
 a missing option argument
 it returns
 .Dv HOPTERR
 (and writes an error message to the
 .Em stderr 
 if
 .Fn hopterr
 is used to turn error reporting on.)
 .Sh EXAMPLE
 .Bd -literal -compact
 struct h_opt opts[] = {
     { 0, "css",    0,  1, "css file" },
     { 1, "header", 0,  1, "header file" },
     { 2, 0,       'a', 0, "option a (no arg)" },
     { 3, 0,       'b', 1, "option B (with arg)" },
     { 4, "help",  '?', 0, "help message" },
 } ;
 
 #define NROPT (sizeof opts/sizeof opts[0])
 
 
 int
 main(argc, argv)
 char **argv;
 {
     struct h_opt *ret;
     struct h_context ctx;
 
     hoptset(&ctx, argc, argv);
     hopterr(&ctx, 1);
 
     while (( ret = gethopt(&ctx, opts, NROPT) )) {
 
         if ( ret != HOPTERR ) {
             if ( ret->optword )
                 printf("%s", ret->optword);
             else
                 printf("%c", ret->optchar);
 
             if ( ret->opthasarg ) {
                 if ( hoptarg(&ctx) )
                     printf(" = %s", hoptarg(&ctx));
                 else
                     printf(" with no argument?");
             }
             puts(ret->optdesc ? ret->optdesc : "");
         }
     }
 
     argc -= hoptind(&ctx);
     argv += hoptind(&ctx);
 
 .Ed
 .Sh HISTORY
 The
 .Fn gethopt
 function was a quick hack to replace manually parsing full-word arguments
 in 
 .Va discount .