flag2

Package for handling flags, config files, and environment vars

The API was suggested by Peter Bourgan in his Go for Industrial Programming talk.

Base assumptions

• Backward compatible with flag package.
• Existing code that uses the flag package that is ported to flag2 should behave identically until you add options purposefully changing things.
  • Only look at config and EnvVar if the extra flag options are given to look there (i.e. only look in the config file if a flag2.File(name) option is given, only look at EnvVars if a flag2.Env(name) is given).
  • You can use the flag2.UseDefaultNamesInEnvVars() or flag2.UseDefaultNamesInConfigFile() parse options to check EnvVar and Config file for ALL flags using their given names.

Code examples

var (
    foo = flag2.String("foo", "x", "foo val")
    bar = flag2.String("bar", "y", "bar val", flag2.File("bar"))
    baz = flag2.String("baz", "z", "baz val", flag2.File("baz"), flag2.Env("BAZ"))
    cfg = flag2.String("cfg", "", "JSON config file")
)
flag2.Parse(flag2.JSONFileVia("cfg"), flag2.AddEnvPrefix("MYAPP_"))

Or as a flag set using the defaults when parsing:

var fs flag2.FlagSet
var (
    foo = fs.String("foo", "x", "foo val")
    bar = fs.String("bar", "y", "bar val")
    baz = fs.String("baz", "z", "baz val")
    cfg = fs.String("cfg", "", "JSON config file")
)
fs.Parse(os.Args, 
        UseDefaultNamesInEnvVars(),
        UseDefaultNamesInConfigFile(),
        flag2.JSONFileVia("cfg"), 
        flag2.AddEnvPrefix("MYAPP_"))