[asterisk-users] How to get ConfBridge user count

[Steve Johnson]

I want to set up a conference call to be recorded automatically, so
I'd like the recording to start when the second caller joins the
conference (one caller already there).  The recording would continue
until the last user hangs up.

How can you determine how many are already in the conference bridge?

[conferences]
exten => 66,1,Answer
exten => 66,n,Wait(1)
exten => 66,n,Authenticate(123456)
;
exten => 66,n,NoOp(-- ConfBridge 66 user count: ${count} --)
;<-- WHAT VARIABLE TO USE HERE?
;
exten => s,n,Set(MONITOR_EXEC=/etc/asterisk/monitor_exec.sh)
exten => s.,n,Set(DATETIME=${STRFTIME(${EPOCH},,%C%y-%m%d-%H%M)})
exten => s,n,ExecIf($[${count} =
1]?Monitor(wav,record-${CALLERID(num)}-${DATETIME},bm))
;
exten =>66,n,ConfBridge(66,Ms)
exten => 66,n,Playback(goodbye)
exten => 66,n,Hangup

Thanks for any info.