printenv.c

busybox最新版的源码:学习和应用的好东东,多的不说了,大家看后再说吧

/* printenv -- minimal clone of BSD printenv(1).

   usage: printenv [varname]

   Chet Ramey
   [e-mail]
*/

/* Copyright (C) 1997-2002 Free Software Foundation, Inc.

   This file is part of GNU Bash, the Bourne Again SHell.

   Bash 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.

   Bash 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 Bash; see the file COPYING.  If not, write to the Free Software
   Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA. */

#include <stdlib.h>
#include <string.h>

extern char **environ;

int
main (argc, argv)
     int argc;
     char **argv;
{
  register char **envp, *eval;
  int len;

  argv++;
  argc--;

  /* printenv */
  if (argc == 0)
    {
      for (envp = environ; *envp; envp++)
	puts (*envp);
      exit (0);
    }

  /* printenv varname */
  len = strlen (*argv);
  for (envp = environ; *envp; envp++)
    {
      if (**argv == **envp && strncmp (*envp, *argv, len) == 0)
	{
	  eval = *envp + len;
	  /* If the environment variable doesn't have an `=', ignore it. */
	  if (*eval == '=')
	    {
	      puts (eval + 1);
	      exit (0);
	    }
	}
    }
  exit (1);
}