coreutils8.32 true命令和源码分析

命令返回正常退出代码

/* Exit with a status code indicating success.
   Copyright (C) 1999-2020 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 of the License, 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, see .  */
 
#include 
#include 
#include 
#include "system.h"
 
/* Act like "true" by default; false.c overrides this.  */
#ifndef EXIT_STATUS
# define EXIT_STATUS EXIT_SUCCESS
#endif
 
#if EXIT_STATUS == EXIT_SUCCESS
# define PROGRAM_NAME "true"
#else
# define PROGRAM_NAME "false"
#endif
 
#define AUTHORS proper_name ("Jim Meyering")
 
/* 用法函数 */
void
usage (int status)
{
  printf (_("\
Usage: %s [ignored command line arguments]\n\
  or:  %s OPTION\n\
"),
          program_name, program_name);
  printf ("%s\n\n",
          _(EXIT_STATUS == EXIT_SUCCESS
            ? N_("Exit with a status code indicating success.")
            : N_("Exit with a status code indicating failure.")));
  fputs (HELP_OPTION_DESCRIPTION, stdout);
  fputs (VERSION_OPTION_DESCRIPTION, stdout);
  printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
  emit_ancillary_info (PROGRAM_NAME);
  exit (status);
}
 
int
main (int argc, char **argv)
{
  /* Recognize --help or --version only if it's the only command-line
     argument.  */
  /* 命令有传入选项时，才进入该if */
  if (argc == 2)
    {
      /* 初始化 */
      initialize_main (&argc, &argv);
      set_program_name (argv[0]);
      setlocale (LC_ALL, "");
      bindtextdomain (PACKAGE, LOCALEDIR);
      textdomain (PACKAGE);
 
      /* Note true(1) will return EXIT_FAILURE in the
         edge case where writes fail with GNU specific options.  */
      atexit (close_stdout);
 
      /* 用法函数 */
      if (STREQ (argv[1], "--help"))
        usage (EXIT_STATUS);
 
      /* 版本信息等 */
      if (STREQ (argv[1], "--version"))
        version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
                     (char *) NULL);
    }
  /* 没有传入选项时，直接返回EXIT_STATUS正常退出代码 */
  return EXIT_STATUS;
}