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From: chip@ateng.ateng.com (Chip Salzenberg)
Newsgroups: comp.unix.wizards
Subject: Re: replacement for putenv()
Message-ID: <1989Feb13.115106.17884@ateng.ateng.com>
Date: 13 Feb 89 16:51:05 GMT
References: <164@bds-ny.UUCP> <549@marob.MASA.COM>
Organization: A T Engineering, Tampa, FL
Lines: 61

Here is a rather nice replacement for putenv().  I wrote it for the BSD port
of my deliver program.  (I know it's source, but it's short.)  Its nicest
feature is the avoidance of memory waste when it is called several times.
---8<---cut here---8<---

int
putenv(s)
char *s;
{
	static  char    **env_array;
	static  int     env_size;
	char    *e;
	int     i, j;

	if (env_array == NULL)
	{
		for (i = 0; environ[i]; ++i)
			{}
		env_size = i + 10;      /* arbitrary */
		env_array = (char **) malloc(env_size * sizeof(char *));
		if (env_array == NULL)
			return 1;
		memcpy((char *)env_array, (char *)environ,
		       (int) ((i + 1) * sizeof(char *)));
		environ = env_array;
	}
	else if (environ != env_array)
		fprintf(stderr, "putenv: warning: someone moved environ!\n");

	if ((e = strchr(s, '=')) != NULL)
		++e;
	else
		e = s + strlen(s);

	j = 0;
	for (i = 0; env_array[i]; ++i)
	{
		if (strncmp(env_array[i], s, e - s) != 0)
			env_array[j++] = env_array[i];
	}

	if ((j + 1) >= env_size)
	{
		env_size += 10;                 /* arbitrary */
		env_array = (char **) realloc((char *)env_array,
					env_size * sizeof(char **));
		if (env_array == NULL)
			return 1;
	}

	env_array[j++] = s;
	env_array[j] = NULL;

	environ = env_array;
	return 0;
}

-- 
Chip Salzenberg             <chip@ateng.com> or <uunet!ateng!chip>
A T Engineering             Me?  Speak for my company?  Surely you jest!
	  "It's no good.  They're tapping the lines."