include all files under a directory

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?

is there any idea?

for dr in *
do
    echo "include $PWD/$dr;"
done

Copy the output of the above code and paste in to your file

This is not the way I expect;
In addition, your code produce the following:

include /home/htao/trial/new/*;

cd /etc/dhcpd/
for dr in *
do
    echo "include $PWD/$dr;"
done

First move the directory where you have the files to include