How to set ENV variable to an apache log directive?

[jbiskofski <jbiskofski@xxxxxxxxx>]

Hello,

Im using Apache 2.0.63 and a module called mod-log-firstbyte that enables a log
directive %F which is very similar %D. The difference is instead of
storing the time it takes to serve the request, it stores the time
between the request being read to the first byte being served.
( http://code.google.com/p/mod-log-firstbyte/ )

Id like to have access to this variable in my web applications. Im
thinking theres a way to use SetEnvIf to set this value, but am unsure
how to proceed.

I unsuccessfully tried this and a few variations :

SetEnvIf Request_URI .* FIRSTBYTE_TIME=%F

I was unable to gather any more clues from the SetEnvIf documentation.

Which I understand as : if the Request_URI matches .* (anything) set
the ENV variable FIRSTBYTE_TIME to the value of %F.

I ended up with an ENV variable set literally to '%F' instead of the
value.

Any help/insight would be very much appreciated.

Thanks!

-Jose Biskofski