/* env - run a program in a modified environment   Copyright (C) 1986, 1991-2003 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  *//* Richard Mlynarik and David MacKenzie *//* Options:   -   -i   --ignore-environment	Construct a new environment from scratch; normally the	environment is inherited from the parent process, except as	modified by other options.   -u variable   --unset=variable	Unset variable VARIABLE (remove it from the environment).	If VARIABLE was not set, does nothing.   variable=value (an arg containing a "=" character)	Set the environment variable VARIABLE to value VALUE.  VALUE	may be of zero length ("variable=").  Setting a variable to a	zero-length value is different from unsetting it.   --	Indicate that the following argument is the program	to invoke.  This is necessary when the program's name	begins with "-" or contains a "=".   The first remaining argument specifies a program to invoke;   it is searched for according to the specification of the PATH   environment variable.  Any arguments following that are   passed as arguments to that program.   If no command name is specified following the environment   specifications, the resulting environment is printed.   This is like specifying a command name of "printenv".   Examples:   If the environment passed to "env" is	{ LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }   env - foo	runs "foo" in a null environment.   env foo	runs "foo" in the environment	{ LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }   env DISPLAY=gnu:0 nemacs	runs "nemacs" in the environment	{ LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks DISPLAY=gnu:0 }   env - LOGNAME=foo /hacks/hack bar baz	runs the "hack" program on arguments "bar" and "baz" in an	environment in which the only variable is "LOGNAME".  Note that	the "-" option clears out the PATH variable, so one should be	careful to specify in which directory to find the program to	call.   env -u EDITOR LOGNAME=foo PATH=/energy -- e=mc2 bar baz	runs the program "/energy/e=mc2" with environment	{ LOGNAME=foo PATH=/energy }*/#include <config.h>#include <stdio.h>#include <getopt.h>#include <sys/types.h>#include <getopt.h>#include "system.h"#include "error.h"#include "closeout.h"/* The official name of this program (e.g., no `g' prefix).  */#define PROGRAM_NAME "env"#define AUTHORS N_ ("Richard Mlynarik and David MacKenzie")int putenv ();extern char **environ;/* The name by which this program was run. */char *program_name;static struct option const longopts[] ={  {"ignore-environment", no_argument, NULL, 'i'},  {"unset", required_argument, NULL, 'u'},  {GETOPT_HELP_OPTION_DECL},  {GETOPT_VERSION_OPTION_DECL},  {NULL, 0, NULL, 0}};voidusage (int status){  if (status != 0)    fprintf (stderr, _("Try `%s --help' for more information.\n"),	     program_name);  else    {      printf (_("\Usage: %s [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n"),	      program_name);      fputs (_("\Set each NAME to VALUE in the environment and run COMMAND.\n\\n\  -i, --ignore-environment   start with an empty environment\n\  -u, --unset=NAME           remove variable from the environment\n\"), stdout);      fputs (HELP_OPTION_DESCRIPTION, stdout);      fputs (VERSION_OPTION_DESCRIPTION, stdout);      fputs (_("\\n\A mere - implies -i.  If no COMMAND, print the resulting environment.\n\"), stdout);      printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);    }  exit (status);}intmain (register int argc, register char **argv, char **envp){  char *dummy_environ[1];  int optc;  int ignore_environment = 0;  program_name = argv[0];  setlocale (LC_ALL, "");  bindtextdomain (PACKAGE, LOCALEDIR);  textdomain (PACKAGE);  atexit (close_stdout);  while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)    {      switch (optc)	{	case 0:	  break;	case 'i':	  ignore_environment = 1;	  break;	case 'u':	  break;	case_GETOPT_HELP_CHAR;	case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);	default:	  usage (2);	}    }  if (optind != argc && !strcmp (argv[optind], "-"))    ignore_environment = 1;  environ = dummy_environ;  environ[0] = NULL;  if (!ignore_environment)    for (; *envp; envp++)      putenv (*envp);  optind = 0;			/* Force GNU getopt to re-initialize. */  while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)    if (optc == 'u')      putenv (optarg);		/* Requires GNU putenv. */  if (optind != argc && !strcmp (argv[optind], "-"))    ++optind;  while (optind < argc && strchr (argv[optind], '='))    putenv (argv[optind++]);  /* If no program is specified, print the environment and exit. */  if (optind == argc)    {      while (*environ)	puts (*environ++);      exit (EXIT_SUCCESS);    }  execvp (argv[optind], &argv[optind]);  {    int exit_status = (errno == ENOENT ? 127 : 126);    error (0, errno, "%s", argv[optind]);    exit (exit_status);  }}