Use a variable in a sed command

Question

I can\'t seem to use a variable in a sed command, for example:

sed \"24s/.*/\"$ct_tname\"/\" file1.sas > file2.sas

I want $ct_tnam

Answer 1

In my case, i just remplaced single quotes by the double ones:

for a in $(cat ext.cnf); do sed -n "/$a$/p" file1 >> file2; done

For now, it's working well...