ct_config set CS_IFILE property is not working?

Hello,

I know that FreeTDS obsoletes usage of interfaces file, but
unfortunately I'm forced to use it. The problem that I have is that it
seems that when I set CS_IFILE property it isn't taken into account,
file from $SYBASE/interfaces is read instead of one set by this call:

ct_config( ctxt_,
				   CS_SET,
				   CS_IFILE,(void*)"/opt/apps/test/interfaces",
				   CS_NULLTERM,
				   NULL) != CS_SUCCEED

I cannot find any reference to CS_IFILE inside:

http://freetds.cvs.sourceforge.net/viewvc/freetds/freetds/src/ctlib/ct.c?revision=1.224&view=markup

1. Can You confirm that I cannot set custom path to interfaces file
using ct_config?
2. What alternatives do I have? I don't want to modify $SYBASE
environment variable and I wouldn't like to use any function outside
ct library?


-- 
Regards,
Darek