Correct syntax to access a shell variable?

I would like to access my shell environment variable MYIP
from within 
sip.conf to put in externip.

I've tried some variations of syntax after reading "The
Future of 
Telephony" but it's not working yet.

Should it be
externip=${ENV{$MYIP}}
or some other syntax??

Larry

-- 
Larry Alkoff N2LA - Austin TX
Using Thunderbird on Linux
_______________________________________________
Austin-Asterisk-Users-Group mailing list
Austin-Asterisk-Users-Groupbybent.com
http://buzzard.onr.com/mailman/listinfo/austi
n-asterisk-users-group
AAUG Web Site: http://aaug.bybent.com/