How to insert a variable into grep?

Question

bash

how to substitute the mask
variable in the test=$( echo $ip | grep -o '^ 192.168. ' )
#!/bin/bash
ip="192.168.33.44"
mask="192.168."
test=$(echo $ip | grep -o '^ 192.168. ')
if [ "$test" != "" ];
then echo OK $ip;
else echo BAD
fi;
PS
the meaning of the script
is to check the IP by mask
give yes / no

Answer 1

Like this:

...
test=$(echo $ip | grep -o "^$mask")
...