oneconf

type cfg struct {
	A bool
	B bool    `default:"t"`
	C bool    `default:"1"`
	D bool    `default:"true"`
	E bool    `default:"false"`
	F int8    `default:"12"`
	G int32   `default:"-12"`
	H uint8   `default:"70"`
	I uint16  `default:"70"`
	J uint32  `default:"0x70"`
	K uint64  `default:"0o70"`
	L uint    `default:"0b10011"`
	M float32 `default:"12e-3"`
	N float64 `default:"12e+1"`
	O string  `default:"text"`
}

c := cfg{}

LoadDefaults(&c)

fmt.Println(c)

Output:

{false true true true false 12 -12 70 70 112 56 19 0.012 120 text}

type cfg struct {
	A bool
	B bool `env:"one"`
	C bool `env:"two"`
	D bool
	E bool
	F int8
	G int32
	H uint8
	I uint16
	J uint32 `env:"THREE"`
	K uint64
	L uint
	M float32
	N float64
	O string
}

os.Setenv("PRE_ONE", "true")
os.Setenv("PRE_TWO", "T")
os.Setenv("PRE_THREE", "0x77") // used to populate J
os.Setenv("PRE_D", "T")
os.Setenv("PRE_E", "F")
os.Setenv("PRE_F", "6")
os.Setenv("PRE_G", "-8")
os.Setenv("PRE_H", "110")
os.Setenv("PRE_I", "0x110")
os.Setenv("PRE_J", "0o110") //ignored since field has a env name
os.Setenv("PRE_K", "0b110")
os.Setenv("PRE_L", "110")
os.Setenv("PRE_M", "1.28e-2")
os.Setenv("PRE_N", "3.1415")
os.Setenv("PRE_O", "my-text")

c := cfg{}

LoadEnv(&c, "PRE_", false) // populate named ones only
fmt.Println(c)

LoadEnv(&c, "PRE_", true) // populate named ones and then by field name
fmt.Println(c)

Output:

{false true true false false 0 0 0 0 119 0 0 0 0 }
{false true true true false 6 -8 110 272 119 6 110 0.0128 3.1415 my-text}

type cfg struct {
	A bool
	B bool
	C bool
	D bool
	E bool
	F int8
	G int32
	H uint8
	I uint16
	J uint32
	K uint64
	L uint
	M float32
	N float64
	O string
}

c := cfg{}
fmt.Println(c)

os.Args = []string{"binary", "-h", "-a"}

LoadFlags(&c, false) // populate named ones only
fmt.Println(c)

LoadFlags(&c, true) // populate named ones and then by field name
fmt.Println(c)

Output:

{d}

type cfg struct {
	A string
	B int
	C []string
	D struct {
		E bool
		F float64
	}
}

toml := `
A = "my-string"
B = 0x110
C = ["one", "two"]

[D]
E = true
F = 12e-1
	`

if err := os.WriteFile("_$_test.toml", []byte(toml), 0o600); err != nil {
	fmt.Println("can not save test file")
	os.Exit(1)
}

c := cfg{}

LoadTOML(&c, "_$_test.toml")

fmt.Print(c)

if err := os.Remove("_$_test.toml"); err != nil {
	fmt.Println("can not remove test file")
	os.Exit(1)
}

Output:

{my-string 272 [one two] {true 1.2}}