/usr/bin/texdoctk is in texlive-base 2009-15.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../share/texmf-texlive/scripts/tetex/texdoctk.pl
/usr/bin/../share/texmf-texlive/scripts/tetex/texdoctk.pl