ngx-helper.lua

--[[ ngx-helper.lua

author: Allex Wang (https://iallex.com/)

## ngx helper

  get_var_names() - get variable names

## tools

```sh
cat <<'EOF' > get-ngx-var-names.sh
#!/bin/bash
# by allex_wang
SH_DIR="$(cd -P -- "$(dirname -- "$(readlink -f "$0")")" && pwd -P)"
curl -s https://nginx.org/en/docs/varindex.html| sed 's#</a>#\n#g' |sed -e '1,/<div id="content">/d' |grep '>\$' |sed 's#.*>\$#\$#g' |sort |uniq > "$SH_DIR/.ngx_var_names"
EOF
```

GistID: 12babbd17917e892658e4312226275d8
GistURL: https://gist.github.com/12babbd17917e892658e4312226275d8

--]]

local _M = {
  -- cache the full ngx var keys (avoid load keys file duplicate
  _var_name_cache = nil
}

function _M.get_var_names()
  if _M._var_name_cache == nil then
    _M._var_name_cache = {
      "http_cookie",
      "http_host",
      "http_origin",
      "http_purge_cache",
      "http_referer",
      "http_user_agent",
      "http_via",
      "http_x_allex",
      "http_x_forwarded_for",
    }
    local var_key_file = ngx.config.prefix() .. "lua/.ngx_var_names"
    local file = io.open(var_key_file, "r")
    print("Start to load: " .. var_key_file)
    if file then
      -- Read the file line by line
      for line in file:lines() do
        table.insert(_M._var_name_cache, line)
      end
      file:close()
    else
      print("Failed to open the file")
    end
  end
  return _M._var_name_cache
end

return _M