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putenv.c

/* Copyright (C) 1991 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., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include <sys/types.h>
#include <errno.h>

#ifndef STDC_HEADERS
extern int errno;
#endif

/* Don't include stdlib.h for non-GNU C libraries because some of them
   contain conflicting prototypes for getopt.
   This needs to come after some library #include
   to get __GNU_LIBRARY__ defined.  */
#ifdef      __GNU_LIBRARY__
#include <stdlib.h>
#else
char *malloc ();
#endif      /* GNU C library.  */

#if defined(STDC_HEADERS) || defined(HAVE_STRING_H)
#include <string.h>
#else
#include <strings.h>
#ifndef strchr
#define strchr index
#endif
#ifndef memcpy
#define memcpy(d, s, n) bcopy((s), (d), (n))
#endif
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifndef NULL
#define NULL 0
#endif

extern char **environ;

/* Put STRING, which is of the form "NAME=VALUE", in the environment.  */
int
putenv (string)
     const char *string;
{
  char *name_end = strchr (string, '=');
  register size_t size;
  register char **ep;

  if (name_end == NULL)
    {
      /* Remove the variable from the environment.  */
      size = strlen (string);
      for (ep = environ; *ep != NULL; ++ep)
      if (!strncmp (*ep, string, size) && (*ep)[size] == '=')
        {
          while (ep[1] != NULL)
            {
            ep[0] = ep[1];
            ++ep;
            }
          *ep = NULL;
          return 0;
        }
    }

  size = 0;
  for (ep = environ; *ep != NULL; ++ep)
    if (!strncmp (*ep, string, name_end - string) &&
      (*ep)[name_end - string] == '=')
      break;
    else
      ++size;

  if (*ep == NULL)
    {
      static char **last_environ = NULL;
      char **new_environ = (char **) malloc ((size + 2) * sizeof (char *));
      if (new_environ == NULL)
      return -1;
      memcpy ((char *) new_environ, (char *) environ, size * sizeof (char *));
      new_environ[size] = (char *) string;
      new_environ[size + 1] = NULL;
      if (last_environ != NULL)
      free ((char *) last_environ);
      last_environ = new_environ;
      environ = new_environ;
    }
  else
    *ep = (char *) string;

  return 0;
}

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