Function erlang_nif_sys::erlang_nif_sys_api::enif_port_command

pub unsafe extern "C" fn enif_port_command(
    env: *mut ErlNifEnv, 
    to_port: *const ErlNifPort, 
    msg_env: *mut ErlNifEnv, 
    msg: ERL_NIF_TERM
) -> c_int

See enif_port_command in the Erlang docs.