When we try to get the doc of a erlang function we got
h :file.write ... Module was compiled without docs. Showing only specs.
We need to use at least OTP 23 and have the dependencies to build the documentation.
sudo apt-get install xsltproc fop KERL_BUILD_DOCS=yes asdf install erlang 23.3.3 asdf local erlang 23.3.3 iex h :file.write Success doc is here !