spf13--viper/README.md

viper
=====

Go configuration with fangs

## What is Viper?

Viper is a complete configuration solution. Designed to work within an
application to handle file based configuration and seamlessly marry that with
command line flags which can also be used to control application behavior.
Viper also supports retrieving configuration values from remote key/value stores. 
Etcd and Consul are supported. 

## Why Viper?

When building a modern application you don’t want to have to worry about
configuration file formats, you want to focus on building awesome software.
Viper is here to help with that.

Viper does the following for you:

1. Find, load and marshall a configuration file in YAML, TOML or JSON.
2. Provide a mechanism to setDefault values for your different configuration options
3. Provide a mechanism to setOverride values for options specified through command line flags.
4. Provide an alias system to easily rename parameters without breaking existing code.
5. Make it easy to tell the difference between when a user has provided a command line or config file which is the same as the default.

Viper believes that:

1. command line flags take precedence over options set in config files
2. config files take precedence over options set in remote key/value stores
3. remote key/value stores take precedence over defaults

Viper configuration keys are case insensitive.

## Usage

### Initialization

	viper.SetConfigName("config") // name of config file (without extension)
	viper.AddConfigPath("/etc/appname/")   // path to look for the config file in
	viper.AddConfigPath("$HOME/.appname")  // call multiple times to add many search paths
	viper.ReadInConfig() // Find and read the config file

### Setting Defaults

	viper.SetDefault("ContentDir", "content")
	viper.SetDefault("LayoutDir", "layouts")
	viper.SetDefault("Indexes", map[string]string{"tag": "tags", "category": "categories"})

### Setting Overrides

    viper.Set("Verbose", true)
    viper.Set("LogFile", LogFile)

### Registering and Using Aliases

    viper.RegisterAlias("loud", "Verbose")

    viper.Set("verbose", true) // same result as next line
    viper.Set("loud", true)   // same result as prior line

    viper.GetBool("loud") // true
    viper.GetBool("verbose") // true

### Getting Values

    viper.GetString("logfile") // case insensitive Setting & Getting
	if viper.GetBool("verbose") {
        fmt.Println("verbose enabled")
	}

### Remote Key/Value Store Support
Viper will read a config string (as JSON, TOML, or YAML) retrieved from a
path in a Key/Value store such as Etcd or Consul.  These values take precedence
over default values, but are overriden by configuration values retrieved from disk, 
flags, or environment variables.

Viper uses [crypt](https://github.com/xordataexchange/crypt) to retrieve configuration
from the k/v store, which means that you can store your configuration values
encrypted and have them automatically decrypted if you have the correct
gpg keyring.  Encryption is optional.

You can use remote configuration in conjunction with local configuration, or
independently of it.  

`crypt` has a command-line helper that you can use to put configurations
in your k/v store. `crypt` defaults to etcd on http://127.0.0.1:4001.

	go get github.com/xordataexchange/crypt/bin/crypt
	crypt set -plaintext /config/hugo.json /Users/hugo/settings/config.json

Confirm that your value was set:

	crypt get -plaintext /config/hugo.json

See the `crypt` documentation for examples of how to set encrypted values, or how
to use Consul.

### Remote Key/Value Store Example - Unencrypted

	viper.AddRemoteProvider("etcd", "http://127.0.0.1:4001","/config/hugo.json")
	viper.SetConfigType("json") // because there is no file extension in a stream of bytes
	err := viper.ReadRemoteConfig()

### Remote Key/Value Store Example - Encrypted

	viper.AddSecureRemoteProvider("etcd","http://127.0.0.1:4001","/config/hugo.json","/etc/secrets/mykeyring.gpg")
	viper.SetConfigType("json") // because there is no file extension in a stream of bytes
	err := viper.ReadRemoteConfig()



## Q & A

Q: Why not INI files?

A: Ini files are pretty awful. There’s no standard format and they are hard to
validate. Viper is designed to work with YAML, TOML or JSON files. If someone
really wants to add this feature, I’d be happy to merge it. It’s easy to
specify which formats your application will permit.

Q: Why is it called "viper"?

A: Viper is designed to be a companion to
[Cobra](http://github.com/spf13/cobra). While both can operate completely
independently, together they make a powerful pair to handle much of your
application foundation needs.

Q: Why is it called "Cobra"?

A: Is there a better name for a commander?