package flag

Import Path
	flag (on golang.org and go.dev)

Dependency Relation
	imports 9 packages, and imported by 4 packages

Involved Source Files
	d-> flag.go

Exported Type Names

type ErrorHandling int ErrorHandling defines how FlagSet.Parse behaves if the parse fails. func (*FlagSet).ErrorHandling() ErrorHandling func NewFlagSet(name string, errorHandling ErrorHandling) *FlagSet func (*FlagSet).Init(name string, errorHandling ErrorHandling) const ContinueOnError const ExitOnError const PanicOnError
type Flag (struct) A Flag represents the state of a flag. DefValue string Name string Usage string Value Value func Lookup(name string) *Flag func (*FlagSet).Lookup(name string) *Flag func UnquoteUsage(flag *Flag) (name string, usage string)
type FlagSet (struct) A FlagSet represents a set of defined flags. The zero value of a FlagSet has no name and has ContinueOnError error handling. Flag names must be unique within a FlagSet. An attempt to define a flag whose name is already in use will cause a panic. Usage func() (*T) Arg(i int) string (*T) Args() []string (*T) Bool(name string, value bool, usage string) *bool (*T) BoolVar(p *bool, name string, value bool, usage string) (*T) Duration(name string, value time.Duration, usage string) *time.Duration (*T) DurationVar(p *time.Duration, name string, value time.Duration, usage string) (*T) ErrorHandling() ErrorHandling (*T) Float64(name string, value float64, usage string) *float64 (*T) Float64Var(p *float64, name string, value float64, usage string) (*T) Init(name string, errorHandling ErrorHandling) (*T) Int(name string, value int, usage string) *int (*T) Int64(name string, value int64, usage string) *int64 (*T) Int64Var(p *int64, name string, value int64, usage string) (*T) IntVar(p *int, name string, value int, usage string) (*T) Lookup(name string) *Flag (*T) NArg() int (*T) NFlag() int (*T) Name() string (*T) Output() io.Writer (*T) Parse(arguments []string) error (*T) Parsed() bool (*T) PrintDefaults() (*T) Set(name, value string) error (*T) SetOutput(output io.Writer) (*T) String(name string, value string, usage string) *string (*T) StringVar(p *string, name string, value string, usage string) (*T) Uint(name string, value uint, usage string) *uint (*T) Uint64(name string, value uint64, usage string) *uint64 (*T) Uint64Var(p *uint64, name string, value uint64, usage string) (*T) UintVar(p *uint, name string, value uint, usage string) (*T) Var(value Value, name string, usage string) (*T) Visit(fn func(*Flag)) (*T) VisitAll(fn func(*Flag)) func NewFlagSet(name string, errorHandling ErrorHandling) *FlagSet var CommandLine *FlagSet
type Getter (interface) Getter is an interface that allows the contents of a Value to be retrieved. It wraps the Value interface, rather than being part of it, because it appeared after Go 1 and its compatibility rules. All Value types provided by this package satisfy the Getter interface. (T) Get() interface{} (T) Set(string) error (T) String() string T : Value T : expvar.Var T : fmt.Stringer
type Value (interface) Value is the interface to the dynamic value stored in a flag. (The default value is represented as a string.) If a Value has an IsBoolFlag() bool method returning true, the command-line parser makes -name equivalent to -name=true rather than using the next command-line argument. Set is called once, in command line order, for each flag present. The flag package may call the String method with a zero-valued receiver, such as a nil pointer. (T) Set(string) error (T) String() string Getter (interface) T : expvar.Var T : fmt.Stringer func Var(value Value, name string, usage string) func (*FlagSet).Var(value Value, name string, usage string)
Exported Values
func Arg(i int) string Arg returns the i'th command-line argument. Arg(0) is the first remaining argument after flags have been processed. Arg returns an empty string if the requested element does not exist.
func Args() []string Args returns the non-flag command-line arguments.
func Bool(name string, value bool, usage string) *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(p *bool, name string, value bool, usage string) 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.
var CommandLine *FlagSet CommandLine is the default set of command-line flags, parsed from os.Args. The top-level functions such as BoolVar, Arg, and so on are wrappers for the methods of CommandLine.
const ContinueOnError ErrorHandling = 0 // Return a descriptive error. These constants cause FlagSet.Parse to behave as described if the parse fails.
func Duration(name string, value time.Duration, usage string) *time.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. The flag accepts a value acceptable to time.ParseDuration.
func DurationVar(p *time.Duration, name string, value time.Duration, usage string) 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. The flag accepts a value acceptable to time.ParseDuration.
var ErrHelp error ErrHelp is the error returned if the -help or -h flag is invoked but no such flag is defined.
const ExitOnError ErrorHandling = 1 // Call os.Exit(2) or for -h/-help Exit(0). These constants cause FlagSet.Parse to behave as described if the parse fails.
func Float64(name string, value float64, usage string) *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(p *float64, name string, value float64, usage string) 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(name string, value int, usage string) *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(name string, value int64, usage string) *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(p *int64, name string, value int64, usage string) 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(p *int, name string, value int, usage string) 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(name string) *Flag Lookup returns the Flag structure of the named command-line flag, returning nil if none exists.
func NArg() int NArg is the number of arguments remaining after flags have been processed.
func NewFlagSet(name string, errorHandling ErrorHandling) *FlagSet NewFlagSet returns a new, empty flag set with the specified name and error handling property. If the name is not empty, it will be printed in the default usage message and in error messages.
func NFlag() int NFlag returns the number of command-line flags that have been set.
const PanicOnError ErrorHandling = 2 // Call panic with a descriptive error. These constants cause FlagSet.Parse to behave as described if the parse fails.
func Parse() Parse parses the command-line flags from os.Args[1:]. Must be called after all flags are defined and before flags are accessed by the program.
func Parsed() bool Parsed reports whether the command-line flags have been parsed.
func PrintDefaults() PrintDefaults prints, to standard error unless configured otherwise, a usage message showing the default settings of all defined command-line flags. For an integer valued flag x, the default output has the form -x int usage-message-for-x (default 7) The usage message will appear on a separate line for anything but a bool flag with a one-byte name. For bool flags, the type is omitted and if the flag name is one byte the usage message appears on the same line. The parenthetical default is omitted if the default is the zero value for the type. The listed type, here int, can be changed by placing a back-quoted name in the flag's usage string; the first such item in the message is taken to be a parameter name to show in the message and the back quotes are stripped from the message when displayed. For instance, given flag.String("I", "", "search `directory` for include files") the output will be -I directory search directory for include files. To change the destination for flag messages, call CommandLine.SetOutput.
func Set(name, value string) error Set sets the value of the named command-line flag.
func String(name string, value string, usage string) *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(p *string, name string, value string, usage string) 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(name string, value uint, usage string) *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(name string, value uint64, usage string) *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(p *uint64, name string, value uint64, usage string) 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(p *uint, name string, value uint, usage string) 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.
func UnquoteUsage(flag *Flag) (name string, usage string) UnquoteUsage extracts a back-quoted name from the usage string for a flag and returns it and the un-quoted usage. Given "a `name` to show" it returns ("name", "a name to show"). If there are no back quotes, the name is an educated guess of the type of the flag's value, or the empty string if the flag is boolean.
var Usage func() Usage prints a usage message documenting all defined command-line flags to CommandLine's output, which by default is os.Stderr. It is called when an error occurs while parsing flags. The function is a variable that may be changed to point to a custom function. By default it prints a simple header and calls PrintDefaults; for details about the format of the output and how to control it, see the documentation for PrintDefaults. Custom usage functions may choose to exit the program; by default exiting happens anyway as the command line's error handling strategy is set to ExitOnError.
func Var(value Value, name string, usage string) Var defines a flag with the specified name and usage string. The type and value of the flag are represented by the first argument, of type Value, which typically holds a user-defined implementation of Value. For instance, the caller could create a flag that turns a comma-separated string into a slice of strings by giving the slice the methods of Value; in particular, Set would decompose the comma-separated string into the slice.
func Visit(fn func(*Flag)) Visit visits the command-line flags in lexicographical order, calling fn for each. It visits only those flags that have been set.
func VisitAll(fn func(*Flag)) VisitAll visits the command-line flags in lexicographical order, calling fn for each. It visits all flags, even those not set.