The following command generates a 20 character password
from all visible ASCII characters (94)
except '"|\
(90),
which are problematic in some contexts,
like embedding in (unversioned) source code,
for approximately 128 bits of entropy (9020 = 1.22e+39):
$ < /dev/urandom tr -dc [:graph:] | tr -d \|\\\'\\\\\" | head -c20 | xsel --clipboard