[FROG] [FRR] [syslog] How to dump log of bgpd

Hi all, I'm using FRR, I found zebra, staticd could dump log, but bgpd could not I start bgpd like this:

root@NX-ZWYC-M1F202-A16-HW6865-A-INT-212:/# /usr/lib/frr/bgpd -A 127.0.0.1 -M snmp --log stdout --log-level debug

There is only this log:

2019/08/22 07:21:43 BGP: bgpd 7.0.1-sonic starting: vty@2605, bgp@ <all>:179

Then I up/down peer, there is no log ---- Simon Jones