/usr/share/man/man3/Tcl_FSGetCwd.3tcl.gz is in tcl8.6-doc 8.6.1-4ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man3/Tcl_FSRegister.3tcl.gz
/usr/share/man/man3/Tcl_FSRegister.3tcl.gz