Greetings,

I have a Contact URI with params as in the following form returned to me in a 302 Moved Temporarily reply:

sip:a=foo;b;c=bar

I am able to check the existence of parameters 'a' and 'b', which have values assigned to them, in the following way:

failure_route[...] { ... $var(dest) = $T_rpl($ct); $var(dest) = $(var(dest){nameaddr.uri}); $var(dest) = $(var(dest){uri.user}); ... if(! $(var(dest){param.value,a})) { .... } ... }

However, what I cannot seem to figure out is a reliable test condition for the existence of a parameter like 'b', which does not have a value. I have tried:

if(! $(var(dest){param.value,b}))

which clearly cannot work as the parameter has no _value_.

Also have tried:

if(!defined $(var(dest){param.value,b}))

and also tests of strempty(), !defined, etc. for $var(dest){uri.param,b}) (prior to extraction of param list using {uri.user} above).

Ideas appreciated, thanks!