Re: Just want to exclude lines with tabs

    grep "$(printf '\t')" o.csv

It seems to me this should have worked, unless your shell's quoting got
rid of the \ before printf could see it.  Certainly this works:

tab=`printf '\t'`  # or $(...), whatever
grep "$tab" somefile

This assignment of special characters to shell variables and then using
the variable in subsequent commands is the most portable (across decades
and "improvements" in standards, shells, systems, ...) approach I know
of.  FWIW.  -k