golift.io/cnfg

Overview

Procedures for parsing config files and environment variables into data structures. Works much like json.Unmarshal and json.Marshal. Short explanation on how the env variable mapping works below. See GoDoc for several working examples and further explanation of how maps and slices can be accessed with shell env vars.

Supports all base types, including slices, maps, slices of maps, maps of slices, pointers of slices to maps of slices full of ints, strings, floats and the like!

Please open an issue if you run into a bug or an unsupported type.

Better documentation is needed. Most of it is in GoDoc. This package is full featured for environment variable parsing!

Bonus, it goes the other way too. You can convert a data structure into environment variables. This is useful when you wish to pass a lot of data into a command via exec.Command. Simply set the data into a struct, marshal it into environment variables and pass it in.

Examples

type Shelter struct {
	Title  string    `xml:"title"`
	Sym    float64   `xml:"sym"`
	People []*Person `xml:"people"`
	Dogs   []*Dog    `xml:"dogs"`
}

type Person struct {
	Name    string `xml:"name"`
	Present bool   `xml:"present"`
	Age     int    `xml:"age"`
	ID      int64  `xml:"id"`
}

type Dog struct {
	Name    string
	Elapsed config.Duration
	Owners  []string
}

type Config struct {
	*Shelter `xml:"shelter"`
}

The above struct can be configured with the following environment variables, assuming you set prefix := "APP" when you call UnmarshalENV(). Slices use env vars with numbers in them, starting at 0 and going to infinity, or the last env var provided + 1, whichever comes first. It just works. The ... and ++ indicate that those parameters belong to slices, and many items may be appended or overridden.

APP_SHELTER_TITLE
APP_SHELTER_SYM
APP_SHELTER_PEOPLE_0_NAME
APP_SHELTER_PEOPLE_0_PRESENT
APP_SHELTER_PEOPLE_0_AGE
APP_SHELTER_PEOPLE_0_ID
APP_SHELTER_PEOPLE_1_NAME
...
APP_SHELTER_PEOPLE_10_ID ++

APP_SHELTER_DOGS_0_NAME
APP_SHELTER_DOGS_0_ELAPSED
APP_SHELTER_DOGS_0_OWNERS_0
...
APP_SHELTER_DOGS_0_OWNERS_10 ++

APP_SHELTER_DOGS_1_NAME
APP_SHELTER_DOGS_1_ELAPSED
APP_SHELTER_DOGS_1_OWNERS_0
APP_SHELTER_DOGS_1_OWNERS_1 ++

If you passed in the Shelter struct instead of Config, all the of the SHELTER_ portions of the tags would be omitted. You can also set which struct tag to use by creating an &ENV{} pointer and setting Tag and/or Pfx . Tag defaults to "xml", but you could set it to "env" and make custom names for env variables. The env var prefix Pfx is optional, but recommended.