coreutils/lib/putenv.c

/* Copyright (C) 1991, 1994 Free Software Foundation, Inc.


NOTE: The canonical source of this file is maintained with the GNU C Library.
Bugs can be reported to bug-glibc@prep.ai.mit.edu.

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.  */

#include <errno.h>

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

/* Define-away any (possibly conflicting) prototype of putenv.
   Many systems omit the `const' attribute on the argument.  */
#define putenv _sys_putenv

#if defined (__GNU_LIBRARY__) || defined (HAVE_STDLIB_H)
# include <stdlib.h>
#endif
#if defined (__GNU_LIBRARY__) || defined (HAVE_STRING_H)
# include <string.h>
#endif
#if defined (__GNU_LIBRARY__) || defined (HAVE_UNISTD_H)
# include <unistd.h>
#endif

#undef putenv

#if !defined (__GNU_LIBRARY__) && !defined (HAVE_STRCHR)
# define strchr index
#endif
#if !defined (__GNU_LIBRARY__) && !defined (HAVE_MEMCPY)
# define memcpy(d,s,n) bcopy ((s), (d), (n))
#endif

#if HAVE_GNU_LD
# define environ __environ
#else
extern char **environ;
#endif


/* Put STRING, which is of the form "NAME=VALUE", in the environment.  */
int
putenv (string)
     const char *string;
{
  const char *const 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;
      (void) memcpy ((void *) new_environ, (void *) environ,
		     size * sizeof (char *));
      new_environ[size] = (char *) string;
      new_environ[size + 1] = NULL;
      if (last_environ != NULL)
	free ((void *) last_environ);
      last_environ = new_environ;
      environ = new_environ;
    }
  else
    *ep = (char *) string;

  return 0;
}