dhcp include

I want to include all the subnet files under /etc/dhcpd/ to /etc/dhcpd.conf

so here is my content of dhcpd.conf

...
include "/etc/dhcpd/*";

however, the check-syntax reports syntax error, as they do not recognize the wildcard , and display that " file /etc/dhcpd/ could not be found.

how can I use wildcard to refer to all the files in this directory?

Thread closed, this is a duplicate.