超强hello world


作者:lingyun 来源:凌云物网智科实验室 时间:2014-01-13

Links: http://packages.debian.org/unstable/devel/hello

从Hello.c来看看Linux下C语言的编程

hello.c 

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

Copyright (C) 1992, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
2005, 2006 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 2, 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/null 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: GNU GPL v2+ <http://www.gnu.org/licenses/gpl.html>\n\
This is free software. There is NO WARRANTY, to the extent permitted by law.\n”),
“2006”);
}

头文件:system.h

/* system.h: system-dependent declarations; include this first.
Copyright (C) 1996, 2005, 2006 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 2, 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. */

#ifndef HELLO_SYSTEM_H
#define HELLO_SYSTEM_H

/* Assume ANSI C89 headers are available. */
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Use POSIX headers. If they are not available, we use the substitute
provided by gnulib. */
#include <getopt.h>
#include <unistd.h>

/* Internationalization. */
#include “gettext.h”
#define _(str) gettext (str)
#define N_(str) gettext_noop (str)

/* Check for errors on write. */
#include “closeout.h”

#endif /* HELLO_SYSTEM_H */

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