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Does the library have a "Hello, World" project similar to GNU?

GNU Hello is an example of a GNU project for best practices, coding standards, internationalization, configuration automation, etc.

Is there a similar project designed for libraries? I understand that GNU Hello can be used this way, but would some library-related methods be missing?

I also searched for good tutorials on this topic, and the “HOWTO Program Library” seems to be the most suitable. Do you have any other suggestions?

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I read the GNU manual and found a short example that I think will help you get started well:

Directly from the manual:

/* hello.c -- print a greeting message and exit.

    Copyright (C) 1992, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
    2005, 2006, 2007 Free Software Foundation, Inc.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3, or (at your option)
    any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software Foundation,
    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

 #include <config.h>
 #include "system.h"

 /* String containing name the program is called with.  */
 const char *program_name;

 static const struct option longopts[] =
 {
   { "greeting", required_argument, NULL, 'g' },
   { "help", no_argument, NULL, 'h' },
   { "next-generation", no_argument, NULL, 'n' },
   { "traditional", no_argument, NULL, 't' },
   { "version", no_argument, NULL, 'v' },
   { NULL, 0, NULL, 0 }
 };

 static void print_help (void);
 static void print_version (void);

 int
 main (int argc, char *argv[])
 {
   int optc;
   int t = 0, n = 0, lose = 0;
   const char *greeting = NULL;

   program_name = argv[0];

   /* Set locale via LC_ALL.  */
   setlocale (LC_ALL, "");

 #if ENABLE_NLS
   /* Set the text message domain.  */
   bindtextdomain (PACKAGE, LOCALEDIR);
   textdomain (PACKAGE);
 #endif

   /* Even exiting has subtleties.  The /dev/full device on GNU/Linux
      can be used for testing whether writes are checked properly.  For
      instance, hello >/dev/full should exit unsuccessfully.  On exit,
      if any writes failed, change the exit status.  This is
      implemented in the Gnulib module "closeout".  */
   atexit (close_stdout);

   while ((optc = getopt_long (argc, argv, "g:hntv", longopts, NULL)) != -1)
     switch (optc)
       {
       /* One goal here is having --help and --version exit immediately,
          per GNU coding standards.  */
       case 'v':
         print_version ();
         exit (EXIT_SUCCESS);
         break;
       case 'g':
         greeting = optarg;
         break;
       case 'h':
         print_help ();
         exit (EXIT_SUCCESS);
         break;
       case 'n':
         n = 1;
         break;
       case 't':
         t = 1;
         break;
       default:
         lose = 1;
         break;
       }

   if (lose || optind < argc)
     {
       /* Print error message and exit.  */
       if (optind < argc)
         fprintf (stderr, _("%s: extra operand: %s\n"),
         program_name, argv[optind]);
       fprintf (stderr, _("Try `%s --help' for more information.\n"),
                program_name);
       exit (EXIT_FAILURE);
     }

   /* Print greeting message and exit. */
   if (t)
     printf (_("hello, world\n"));

   else if (n)
     /* TRANSLATORS: Use box drawing characters or other fancy stuff
        if your encoding (e.g., UTF-8) allows it.  If done so add the
        following note, please:

        [Note: For best viewing results use a UTF-8 locale, please.]
     */
    printf (_("\
 +---------------+\n\
 | Hello, world! |\n\
 +---------------+\n\
 "));

   else
     {
       if (!greeting)
         greeting = _("Hello, world!");
       puts (greeting);
     }

   exit (EXIT_SUCCESS);
 }


 
 /* Print help info.  This long message is split into
    several pieces to help translators be able to align different
    blocks and identify the various pieces.  */

 static void
 print_help (void)
 {
   /* TRANSLATORS: --help output 1 (synopsis)
      no-wrap */
         printf (_("\
 Usage: %s [OPTION]...\n"), program_name);

   /* TRANSLATORS: --help output 2 (brief description)
      no-wrap */
   fputs (_("\
 Print a friendly, customizable greeting.\n"), stdout);

   puts ("");
   /* TRANSLATORS: --help output 3: options 1/2
      no-wrap */
   fputs (_("\
   -h, --help          display this help and exit\n\
   -v, --version       display version information and exit\n"), stdout);

   puts ("");
   /* TRANSLATORS: --help output 4: options 2/2
      no-wrap */
   fputs (_("\
   -t, --traditional       use traditional greeting format\n\
   -n, --next-generation   use next-generation greeting format\n\
   -g, --greeting=TEXT     use TEXT as the greeting message\n"), stdout);

   printf ("\n");
   /* TRANSLATORS: --help output 5 (end)
      TRANSLATORS: the placeholder indicates the bug-reporting address
      for this application.  Please add _another line_ with the
      address for translation bugs.
      no-wrap */
   printf (_("\
 Report bugs to <%s>.\n"), PACKAGE_BUGREPORT);
 }


 
 /* Print version and copyright information.  */

 static void
 print_version (void)
 {
   printf ("hello (GNU %s) %s\n", PACKAGE, VERSION);
   /* xgettext: no-wrap */
   puts ("");

   /* It is important to separate the year from the rest of the message,
      as done here, to avoid having to retranslate the message when a new
      year comes around.  */
   printf (_("\
 Copyright (C) %s Free Software Foundation, Inc.\n\
 License GPLv3+: GNU GPL version 3 or later\
 <http://gnu.org/licenses/gpl.html>\n\
 This is free software: you are free to change and redistribute it.\n\
 There is NO WARRANTY, to the extent permitted by law.\n"),
               "2007");
 }
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Source: https://habr.com/ru/post/1774862/

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