rem: 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; }
add: return unsetenv (string);
context: rpl_putenv (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;}