getopt

package module
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 Go to latest Published: Dec 18, 2020 License: BSD-3-Clause Imports: 9 Imported by: 50

README

getopt godoc builds.sr.ht status

A POSIX-compatible getopt implementation for Go, because POSIX getopt is The Correct Way to interpret arguments to command line utilities.

Please send patches/bugs/feedback to ~sircmpwn/public-inbox@lists.sr.ht.

Example Usage

import (
	"os"
	"git.sr.ht/~sircmpwn/getopt"
)

func main() {
	opts, optind, err := getopt.Getopts(os.Args, "abc:d:")
	if err != nil {
		panic(err)
	}
	for _, opt := range opts {
		switch opt.Option {
		case 'a':
			println("Option -a specified")
		case 'b':
			println("Option -b specified")
		case 'c':
			println("Option -c specified: " + opt.Value)
		case 'd':
			println("Option -d specified: " + opt.Value)
		}
	}
	println("Remaining arguments:")
	for _, arg := range os.Args[optind:] {
		println(arg)
	}
}

A flag-like interface is also supported.

import (
	"git.sr.ht/~sircmpwn/getopt"
)

func main() {
	a := getopt.Bool("a", false, "turn on option a")
	b := getopt.Int("b", 1, "set b to a numerical value")
	var opt string
	getopt.StringVar(&opt, "c", "", "let c be specified string")

	err := getopt.Parse()
	if err != nil {
		panic(err)
	}

	print("Value of a: ")
	println(*a)
	print("Value of b: ")
	println(*b)
	println("Value of c: " + opt)

	println("Remaining arguments:")
	for _, arg := range getopt.Args() {
		println(arg)
	}
}

Documentation

Overview

getopt is a POSIX-compatible implementation of getopt(3) for Go.

Example usage: 

import (
	"os"
	"git.sr.ht/~sircmpwn/getopt"
)

func main() {
	opts, optind, err := getopt.Getopts(os.Args, "abc:d:")
	if err != nil {
		panic(err)
	}
	for _, opt := range opts {
		switch opt.Option {
		case 'a':
			println("Option -a specified")
		case 'b':
			println("Option -b specified")
		case 'c':
			println("Option -c specified: " + opt.Value)
		case 'd':
			println("Option -d specified: " + opt.Value)
		}
	}
	println("Remaining arguments:")
	for _, arg := range os.Args[optind:] {
		println(arg)
	}
}

A flag0-like interface is also supported. 

import (
	"git.sr.ht/~sircmpwn/getopt"
)

func main() {
	a := getopt.Bool("a", false, "turn on option a")
	b := getopt.Int("b", 1, "set b to a numerical value")
	var opt string
	getopt.StringVar(&opt, "c", "", "let c be specified string")

	err := getopt.Parse()
	if err != nil {
		panic(err)
	}

	print("Value of a: ")
	println(*a)
	print("Value of b: ")
	println(*b)
	println("Value of c: " + opt)

	println("Remaining arguments:")
	for _, arg := range getopt.Args() {
		println(arg)
	}
}

Index

Constants

This section is empty.

Variables

View Source 
var CommandLine = NewFlagSet(os.Args[0], flag.ExitOnError)

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.

View Source 
var Usage = CommandLine.Usage

Usage prints a usage message documenting all defined command-line flags to 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.

Functions

func Arg 

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 

func Args() []string

Args returns the non-flag command-line arguments.

func Bool 

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 

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.

func Duration 

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 

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.

func Float64 

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 

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 

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 

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 

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 

func IntVar(p *int, name string, value int, usage string)

IntVar defines a int flag with specified name, default value, and usage string. The argument p points to a int variable in which to store the value of the flag.

func NArg 

func NArg() int

NArg is the number of arguments remaining after flags have been processed.

func NFlag 

func NFlag() int

NFlag returns the number of command-line flags that have been set.

func Parse 

func Parse() error

Parse parses the command-line flags from os.Args. Must be called after all flags are defined and before flags are accessed by the program.

func Parsed 

func Parsed() bool

Parsed reports whether the command-line flags have been parsed.

func PrintDefaults 

func PrintDefaults()

PrintDefaults prints, to standard error unless configured otherwise, a usage message showing the default settings of all defined command-line flags.

func Set 

func Set(name, value string) error

Set sets the value of the named flag.

func SetOutput 

func SetOutput(output io.Writer)

SetOutput sets the destination for usage and error messages. If output is nil, os.Stderr is used.

func String 

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 

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 

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 

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 

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 

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 Var 

func Var(value flag.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.

Types

type Flag 

type Flag struct {
	Name  string
	Rune  rune
	Value flag.Value
	Usage string
	// contains filtered or unexported fields
}

A Flag represents the state of a flag.

func Lookup 

func Lookup(name string) *Flag

Lookup returns the Flag structure of the named flag, returning nil if none exists.

type FlagSet 

type FlagSet struct {
	Usage func()
	// contains filtered or unexported fields
}

A FlagSet represents a set of defined flags. The zero value of a FlagSet has no name and has ContinueOnError error handling.

func NewFlagSet 

func NewFlagSet(name string, err flag.ErrorHandling) *FlagSet

NewFlagSet returns a new, empty flag set.

func (*FlagSet) Arg 

func (set *FlagSet) 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 (*FlagSet) Args 

func (set *FlagSet) Args() []string

Args returns the non-flag command-line arguments.

func (*FlagSet) Bool 

func (set *FlagSet) 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 (*FlagSet) BoolVar 

func (set *FlagSet) 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.

func (*FlagSet) Duration 

func (set *FlagSet) 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 (*FlagSet) DurationVar 

func (set *FlagSet) 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.

func (*FlagSet) ErrorHandling 

func (set *FlagSet) ErrorHandling() flag.ErrorHandling

ErrorHandling returns the error handling behavior of the flag set.

func (*FlagSet) Float64 

func (set *FlagSet) 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 (*FlagSet) Float64Var 

func (set *FlagSet) 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 (*FlagSet) Int 

func (set *FlagSet) 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 (*FlagSet) Int64 

func (set *FlagSet) 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 (*FlagSet) Int64Var 

func (set *FlagSet) 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 (*FlagSet) IntVar 

func (set *FlagSet) IntVar(p *int, name string, value int, usage string)

IntVar defines a int flag with specified name, default value, and usage string. The argument p points to a int variable in which to store the value of the flag.

func (*FlagSet) Lookup 

func (set *FlagSet) Lookup(name string) *Flag

Lookup returns the Flag structure of the named flag, returning nil if none exists.

func (*FlagSet) NArg 

func (set *FlagSet) NArg() int

NArg is the number of arguments remaining after flags have been processed.

func (*FlagSet) NFlag 

func (set *FlagSet) NFlag() int

NFlag returns the number of command-line flags that have been set.

func (*FlagSet) Output 

func (set *FlagSet) Output() io.Writer

Output returns the destination for usage and error messages. os.Stderr is returned if output was not set or was set to nil.

func (*FlagSet) Parse 

func (set *FlagSet) Parse() error

Parse parses the command-line flags from os.Args. Must be called after all flags are defined and before flags are accessed by the program.

func (*FlagSet) ParseSlice 

func (set *FlagSet) ParseSlice(args []string) (err error)

ParseSlice parses the command-line flags from args. Must be called after all flags are defined and before flags are accessed by the program.

func (*FlagSet) Parsed 

func (set *FlagSet) Parsed() bool

Parsed reports whether the command-line flags have been parsed.

func (*FlagSet) PrintDefaults 

func (set *FlagSet) PrintDefaults()

PrintDefaults prints, to standard error unless configured otherwise, a usage message showing the default settings of all defined command-line flags.

func (*FlagSet) Set 

func (set *FlagSet) Set(name, value string) error

Set sets the value of the named flag.

func (*FlagSet) SetOutput 

func (set *FlagSet) SetOutput(output io.Writer)

SetOutput sets the destination for usage and error messages. If output is nil, os.Stderr is used.

func (*FlagSet) String 

func (set *FlagSet) 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 (*FlagSet) StringVar 

func (set *FlagSet) 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 (*FlagSet) Uint 

func (set *FlagSet) 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 (*FlagSet) Uint64 

func (set *FlagSet) 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 (*FlagSet) Uint64Var 

func (set *FlagSet) 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 (*FlagSet) UintVar 

func (set *FlagSet) 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 (*FlagSet) Var 

func (set *FlagSet) Var(value flag.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 (*FlagSet) Visit 

func (set *FlagSet) Visit(fn func(*Flag))

Visit visits the command-line flags in lexicographical order, calling fn for each.

func (*FlagSet) VisitAll 

func (set *FlagSet) 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.

type MissingOptionError 

type MissingOptionError rune

This is returned when an option with a mandatory argument is missing that argument.

func (MissingOptionError) Error 

func (e MissingOptionError) Error() string

type Option 

type Option struct {
	Option rune
	Value  string
}

In the case of "-o example", Option is 'o' and "example" is Value. For options which do not take an argument, Value is "".

func Getopts 

func Getopts(argv []string, spec string) ([]Option, int, error)

Getopts implements a POSIX-compatible options interface.

Returns a slice of options and the index of the first non-option argument.

If an error is returned, you must print it to stderr to be POSIX complaint.

type UnknownOptionError 

type UnknownOptionError rune

This is returned when an unknown option is found in argv, but not in the option spec.

func (UnknownOptionError) Error 

func (e UnknownOptionError) Error() string

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