Let’s say that you’re in a system with harmful filenames, for eg.

set lnk = ''to
to  "'

ln -s '  tata  ' $lnk:q

Now I use lnk as argument of a command inside backticks:

echo '=expected output='
readlink $lnk:q
echo =1=
printf '%sn' `readlink $lnk:q`
echo =2=
printf '%sn' "`readlink $lnk:q`"
echo =3=
printf '%sn' "`readlink "$lnk"`"
echo =4=
printf '%sn' "`readlink '$lnk:q'`"

=expected output=
  tata  
=1=
tata
=2=
Unmatched '''.
=3=
Unmatched '`'.
=4=
Unmatched '"'.

What would be the correct way to escape a variable in double-quoted backticks?