Function expandEnv

cmd/cortex/main.go:282–293

expandEnv replaces ${var} or $var in config according to the values of the current environment variables. The replacement is case-sensitive. References to undefined variables are replaced by the empty string. A default value can be given by using the form ${var:default value}.

(config []byte)

// The replacement is case-sensitive. References to undefined variables are replaced by the empty string.
// A default value can be given by using the form ${var:default value}.
func expandEnv(config []byte) []byte {
	return []byte(os.Expand(string(config), func(key string) string {
		keyAndDefault := strings.SplitN(key, ":", 2)
		key = keyAndDefault[0]

		v := os.Getenv(key)
		if v == "" && len(keyAndDefault) == 2 {
			v = keyAndDefault[1] // Set value to the default.
		}
		return v
	}))
}