README
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envflag
Golang flags, but bolted onto the environment rather than the command-line.
Read the godocs.
Motivation
Some like the distinction that command-line flags control behavior while environment variables configure. Also 12-factor recommends the use of environment variables for configuration. The interface of the golang flag package is well designed and easy to use, and allows for other lists (os.Environ() vs os.Args) to be parsed as flags. It makes sense then to use the same interface, the same types, and the same parsing (caveat: there is some ugly string hacking to make environment variables look like flags) to the same ends.
Differences
Calling flag.Parse() will not parse environment flags. Calling
envflag.Parse() will not parse command-line flags. There is no good
reason to combine these two when the net savings is a single line in a
func main(). Furthermore, doing so would require users to accept a
precedence order of my choosing.
The presence of an environment variable named h or help will
probably cause problems (print Usage and os.Exit(0)). Work around this
by defining those flags somewhere (and ignoring them).
Before calling Flagset.Parse on EnvironmentFlags, the environment
variables being passed to Parse are trimmed down using
Lookup. This behavior is different from flag.Parse in that extra
environment variables are ignored (and won't crash envflag.Parse).
Documentation
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Overview ¶
Package envflag adds environment variable flags to the flag package.
Usage:
Define flags using envflag.String(), Bool(), Int(), etc. This package works nearly the same as the stdlib flag package. Parsing the Environment flags is done by calling envflag.Parse()
It will *not* attempt to parse any normally-defined command-line flags. Command-line flags are explicitly left alone and separate.
Index ¶
- Variables
- func Bool(name string, value bool, usage string) *bool
- func BoolVar(p *bool, name string, value bool, usage string)
- func Duration(name string, value time.Duration, usage string) *time.Duration
- func DurationVar(p *time.Duration, name string, value time.Duration, usage string)
- func Float64(name string, value float64, usage string) *float64
- func Float64Var(p *float64, name string, value float64, usage string)
- func Int(name string, value int, usage string) *int
- func Int64(name string, value int64, usage string) *int64
- func Int64Var(p *int64, name string, value int64, usage string)
- func IntVar(p *int, name string, value int, usage string)
- func Lookup(name string) *flag.Flag
- func Parse()
- func Parsed() bool
- func PrintDefaults()
- func Set(name, value string) error
- func String(name string, value string, usage string) *string
- func StringVar(p *string, name string, value string, usage string)
- func Uint(name string, value uint, usage string) *uint
- func Uint64(name string, value uint64, usage string) *uint64
- func Uint64Var(p *uint64, name string, value uint64, usage string)
- func UintVar(p *uint, name string, value uint, usage string)
- func Visit(fn func(*flag.Flag))
- func VisitAll(fn func(*flag.Flag))
Constants ¶
This section is empty.
Variables ¶
var EnvironmentFlags = flag.NewFlagSet("environment", flag.ExitOnError)
EnvironmentFlags is the default set of environment flags, parsed from os.Environ(). The top-level functions such as BoolVar, Arg, and on are wrappers for the methods of EnvironmentFlags.
Functions ¶
func Bool ¶
Bool defines a bool flag with specified name, default value, and usage string. The return value is the address of a bool variable that stores the value of the flag.
func BoolVar ¶
BoolVar defines a bool flag with specified name, default value, and usage string. The argument p points to a bool variable in which to store the value of the flag.
func Duration ¶
Duration defines a time.Duration flag with specified name, default value, and usage string. The return value is the address of a time.Duration variable that stores the value of the flag.
func DurationVar ¶
DurationVar defines a time.Duration flag with specified name, default value, and usage string. The argument p points to a time.Duration variable in which to store the value of the flag.
func Float64 ¶
Float64 defines a float64 flag with specified name, default value, and usage string. The return value is the address of a float64 variable that stores the value of the flag.
func Float64Var ¶
Float64Var defines a float64 flag with specified name, default value, and usage string. The argument p points to a float64 variable in which to store the value of the flag.
func Int ¶
Int defines an int flag with specified name, default value, and usage string. The return value is the address of an int variable that stores the value of the flag.
func Int64 ¶
Int64 defines an int64 flag with specified name, default value, and usage string. The return value is the address of an int64 variable that stores the value of the flag.
func Int64Var ¶
Int64Var defines an int64 flag with specified name, default value, and usage string. The argument p points to an int64 variable in which to store the value of the flag.
func IntVar ¶
IntVar defines an int flag with specified name, default value, and usage string. The argument p points to an int variable in which to store the value of the flag.
func Lookup ¶
Lookup returns the Flag structure of the named environment flag, returning nil if none exists.
func Parse ¶
func Parse()
Parse parses the environment flags from os.Environ. Must be called after all flags are defined and before flags are accessed by the program.
func PrintDefaults ¶
func PrintDefaults()
PrintDefaults prints to standard error the default values of all defined environment flags.
func String ¶
String defines a string flag with specified name, default value, and usage string. The return value is the address of a string variable that stores the value of the flag.
func StringVar ¶
StringVar defines a string flag with specified name, default value, and usage string. The argument p points to a string variable in which to store the value of the flag.
func Uint ¶
Uint defines a uint flag with specified name, default value, and usage string. The return value is the address of a uint variable that stores the value of the flag.
func Uint64 ¶
Uint64 defines a uint64 flag with specified name, default value, and usage string. The return value is the address of a uint64 variable that stores the value of the flag.
func Uint64Var ¶
Uint64Var defines a uint64 flag with specified name, default value, and usage string. The argument p points to a uint64 variable in which to store the value of the flag.
func UintVar ¶
UintVar defines a uint flag with specified name, default value, and usage string. The argument p points to a uint variable in which to store the value of the flag.
Types ¶
This section is empty.
Source Files