8039ca76a5
From-SVN: r171427
498 lines
14 KiB
Go
498 lines
14 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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The flag package implements command-line flag parsing.
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Usage:
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Define flags using flag.String(), Bool(), Int(), etc. Example:
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import "flag"
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var ip *int = flag.Int("flagname", 1234, "help message for flagname")
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If you like, you can bind the flag to a variable using the Var() functions.
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var flagvar int
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func init() {
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flag.IntVar(&flagvar, "flagname", 1234, "help message for flagname")
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}
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Or you can create custom flags that satisfy the Value interface (with
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pointer receivers) and couple them to flag parsing by
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flag.Var(&flagVal, "name", "help message for flagname")
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For such flags, the default value is just the initial value of the variable.
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After all flags are defined, call
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flag.Parse()
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to parse the command line into the defined flags.
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Flags may then be used directly. If you're using the flags themselves,
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they are all pointers; if you bind to variables, they're values.
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fmt.Println("ip has value ", *ip);
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fmt.Println("flagvar has value ", flagvar);
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After parsing, the arguments after the flag are available as the
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slice flag.Args() or individually as flag.Arg(i).
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The arguments are indexed from 0 up to flag.NArg().
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Command line flag syntax:
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-flag
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-flag=x
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-flag x // non-boolean flags only
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One or two minus signs may be used; they are equivalent.
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The last form is not permitted for boolean flags because the
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meaning of the command
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cmd -x *
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will change if there is a file called 0, false, etc. You must
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use the -flag=false form to turn off a boolean flag.
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Flag parsing stops just before the first non-flag argument
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("-" is a non-flag argument) or after the terminator "--".
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Integer flags accept 1234, 0664, 0x1234 and may be negative.
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Boolean flags may be 1, 0, t, f, true, false, TRUE, FALSE, True, False.
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It is safe to call flag.Parse multiple times, possibly after changing
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os.Args. This makes it possible to implement command lines with
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subcommands that enable additional flags, as in:
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flag.Bool(...) // global options
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flag.Parse() // parse leading command
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subcmd := flag.Arg[0]
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switch subcmd {
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// add per-subcommand options
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}
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os.Args = flag.Args()
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flag.Parse()
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*/
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package flag
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import (
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"fmt"
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"os"
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"sort"
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"strconv"
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)
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// -- Bool Value
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type boolValue bool
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func newBoolValue(val bool, p *bool) *boolValue {
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*p = val
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return (*boolValue)(p)
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}
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func (b *boolValue) Set(s string) bool {
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v, err := strconv.Atob(s)
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*b = boolValue(v)
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return err == nil
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}
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func (b *boolValue) String() string { return fmt.Sprintf("%v", *b) }
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// -- Int Value
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type intValue int
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func newIntValue(val int, p *int) *intValue {
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*p = val
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return (*intValue)(p)
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}
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func (i *intValue) Set(s string) bool {
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v, err := strconv.Btoi64(s, 0)
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*i = intValue(v)
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return err == nil
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}
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func (i *intValue) String() string { return fmt.Sprintf("%v", *i) }
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// -- Int64 Value
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type int64Value int64
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func newInt64Value(val int64, p *int64) *int64Value {
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*p = val
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return (*int64Value)(p)
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}
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func (i *int64Value) Set(s string) bool {
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v, err := strconv.Btoi64(s, 0)
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*i = int64Value(v)
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return err == nil
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}
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func (i *int64Value) String() string { return fmt.Sprintf("%v", *i) }
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// -- Uint Value
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type uintValue uint
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func newUintValue(val uint, p *uint) *uintValue {
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*p = val
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return (*uintValue)(p)
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}
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func (i *uintValue) Set(s string) bool {
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v, err := strconv.Btoui64(s, 0)
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*i = uintValue(v)
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return err == nil
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}
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func (i *uintValue) String() string { return fmt.Sprintf("%v", *i) }
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// -- uint64 Value
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type uint64Value uint64
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func newUint64Value(val uint64, p *uint64) *uint64Value {
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*p = val
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return (*uint64Value)(p)
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}
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func (i *uint64Value) Set(s string) bool {
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v, err := strconv.Btoui64(s, 0)
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*i = uint64Value(v)
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return err == nil
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}
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func (i *uint64Value) String() string { return fmt.Sprintf("%v", *i) }
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// -- string Value
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type stringValue string
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func newStringValue(val string, p *string) *stringValue {
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*p = val
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return (*stringValue)(p)
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}
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func (s *stringValue) Set(val string) bool {
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*s = stringValue(val)
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return true
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}
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func (s *stringValue) String() string { return fmt.Sprintf("%s", *s) }
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// -- Float64 Value
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type float64Value float64
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func newFloat64Value(val float64, p *float64) *float64Value {
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*p = val
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return (*float64Value)(p)
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}
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func (f *float64Value) Set(s string) bool {
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v, err := strconv.Atof64(s)
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*f = float64Value(v)
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return err == nil
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}
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func (f *float64Value) String() string { return fmt.Sprintf("%v", *f) }
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// Value is the interface to the dynamic value stored in a flag.
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// (The default value is represented as a string.)
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type Value interface {
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String() string
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Set(string) bool
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}
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// A Flag represents the state of a flag.
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type Flag struct {
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Name string // name as it appears on command line
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Usage string // help message
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Value Value // value as set
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DefValue string // default value (as text); for usage message
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}
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type allFlags struct {
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actual map[string]*Flag
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formal map[string]*Flag
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args []string // arguments after flags
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}
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var flags *allFlags
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// sortFlags returns the flags as a slice in lexicographical sorted order.
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func sortFlags(flags map[string]*Flag) []*Flag {
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list := make(sort.StringArray, len(flags))
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i := 0
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for _, f := range flags {
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list[i] = f.Name
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i++
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}
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list.Sort()
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result := make([]*Flag, len(list))
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for i, name := range list {
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result[i] = flags[name]
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}
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return result
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}
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// VisitAll visits the flags in lexicographical order, calling fn for each.
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// It visits all flags, even those not set.
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func VisitAll(fn func(*Flag)) {
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for _, f := range sortFlags(flags.formal) {
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fn(f)
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}
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}
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// Visit visits the flags in lexicographical order, calling fn for each.
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// It visits only those flags that have been set.
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func Visit(fn func(*Flag)) {
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for _, f := range sortFlags(flags.actual) {
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fn(f)
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}
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}
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// Lookup returns the Flag structure of the named flag, returning nil if none exists.
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func Lookup(name string) *Flag {
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return flags.formal[name]
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}
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// Set sets the value of the named flag. It returns true if the set succeeded; false if
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// there is no such flag defined.
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func Set(name, value string) bool {
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f, ok := flags.formal[name]
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if !ok {
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return false
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}
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ok = f.Value.Set(value)
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if !ok {
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return false
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}
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flags.actual[name] = f
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return true
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}
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// PrintDefaults prints to standard error the default values of all defined flags.
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func PrintDefaults() {
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VisitAll(func(f *Flag) {
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format := " -%s=%s: %s\n"
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if _, ok := f.Value.(*stringValue); ok {
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// put quotes on the value
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format = " -%s=%q: %s\n"
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}
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fmt.Fprintf(os.Stderr, format, f.Name, f.DefValue, f.Usage)
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})
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}
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// Usage prints to standard error a default usage message documenting all defined flags.
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// The function is a variable that may be changed to point to a custom function.
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var Usage = func() {
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fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
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PrintDefaults()
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}
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var panicOnError = false
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// failf prints to standard error a formatted error and Usage, and then exits the program.
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func failf(format string, a ...interface{}) {
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fmt.Fprintf(os.Stderr, format, a...)
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Usage()
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if panicOnError {
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panic("flag parse error")
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}
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os.Exit(2)
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}
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// NFlag returns the number of flags that have been set.
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func NFlag() int { return len(flags.actual) }
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// Arg returns the i'th command-line argument. Arg(0) is the first remaining argument
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// after flags have been processed.
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func Arg(i int) string {
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if i < 0 || i >= len(flags.args) {
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return ""
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}
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return flags.args[i]
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}
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// NArg is the number of arguments remaining after flags have been processed.
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func NArg() int { return len(flags.args) }
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// Args returns the non-flag command-line arguments.
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func Args() []string { return flags.args }
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// BoolVar defines a bool flag with specified name, default value, and usage string.
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// The argument p points to a bool variable in which to store the value of the flag.
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func BoolVar(p *bool, name string, value bool, usage string) {
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Var(newBoolValue(value, p), name, usage)
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}
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// Bool defines a bool flag with specified name, default value, and usage string.
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// The return value is the address of a bool variable that stores the value of the flag.
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func Bool(name string, value bool, usage string) *bool {
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p := new(bool)
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BoolVar(p, name, value, usage)
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return p
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}
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// IntVar defines an int flag with specified name, default value, and usage string.
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// The argument p points to an int variable in which to store the value of the flag.
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func IntVar(p *int, name string, value int, usage string) {
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Var(newIntValue(value, p), name, usage)
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}
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// Int defines an int flag with specified name, default value, and usage string.
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// The return value is the address of an int variable that stores the value of the flag.
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func Int(name string, value int, usage string) *int {
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p := new(int)
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IntVar(p, name, value, usage)
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return p
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}
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// Int64Var defines an int64 flag with specified name, default value, and usage string.
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// The argument p points to an int64 variable in which to store the value of the flag.
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func Int64Var(p *int64, name string, value int64, usage string) {
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Var(newInt64Value(value, p), name, usage)
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}
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// Int64 defines an int64 flag with specified name, default value, and usage string.
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// The return value is the address of an int64 variable that stores the value of the flag.
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func Int64(name string, value int64, usage string) *int64 {
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p := new(int64)
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Int64Var(p, name, value, usage)
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return p
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}
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// UintVar defines a uint flag with specified name, default value, and usage string.
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// The argument p points to a uint variable in which to store the value of the flag.
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func UintVar(p *uint, name string, value uint, usage string) {
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Var(newUintValue(value, p), name, usage)
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}
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// Uint defines a uint flag with specified name, default value, and usage string.
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// The return value is the address of a uint variable that stores the value of the flag.
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func Uint(name string, value uint, usage string) *uint {
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p := new(uint)
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UintVar(p, name, value, usage)
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return p
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}
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// Uint64Var defines a uint64 flag with specified name, default value, and usage string.
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// The argument p points to a uint64 variable in which to store the value of the flag.
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func Uint64Var(p *uint64, name string, value uint64, usage string) {
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Var(newUint64Value(value, p), name, usage)
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}
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// Uint64 defines a uint64 flag with specified name, default value, and usage string.
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// The return value is the address of a uint64 variable that stores the value of the flag.
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func Uint64(name string, value uint64, usage string) *uint64 {
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p := new(uint64)
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Uint64Var(p, name, value, usage)
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return p
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}
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// StringVar defines a string flag with specified name, default value, and usage string.
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// The argument p points to a string variable in which to store the value of the flag.
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func StringVar(p *string, name, value string, usage string) {
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Var(newStringValue(value, p), name, usage)
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}
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// String defines a string flag with specified name, default value, and usage string.
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// The return value is the address of a string variable that stores the value of the flag.
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func String(name, value string, usage string) *string {
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p := new(string)
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StringVar(p, name, value, usage)
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return p
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}
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// Float64Var defines a float64 flag with specified name, default value, and usage string.
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// The argument p points to a float64 variable in which to store the value of the flag.
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func Float64Var(p *float64, name string, value float64, usage string) {
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Var(newFloat64Value(value, p), name, usage)
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}
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// Float64 defines a float64 flag with specified name, default value, and usage string.
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// The return value is the address of a float64 variable that stores the value of the flag.
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func Float64(name string, value float64, usage string) *float64 {
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p := new(float64)
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Float64Var(p, name, value, usage)
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return p
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}
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// Var defines a user-typed flag with specified name, default value, and usage string.
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// The argument p points to a Value variable in which to store the value of the flag.
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func Var(value Value, name string, usage string) {
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// Remember the default value as a string; it won't change.
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f := &Flag{name, usage, value, value.String()}
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_, alreadythere := flags.formal[name]
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if alreadythere {
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fmt.Fprintln(os.Stderr, "flag redefined:", name)
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panic("flag redefinition") // Happens only if flags are declared with identical names
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}
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flags.formal[name] = f
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}
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func (f *allFlags) parseOne() (ok bool) {
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if len(f.args) == 0 {
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return false
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}
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s := f.args[0]
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if len(s) == 0 || s[0] != '-' || len(s) == 1 {
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return false
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}
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num_minuses := 1
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if s[1] == '-' {
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num_minuses++
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if len(s) == 2 { // "--" terminates the flags
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f.args = f.args[1:]
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return false
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}
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}
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name := s[num_minuses:]
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if len(name) == 0 || name[0] == '-' || name[0] == '=' {
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failf("bad flag syntax: %s\n", s)
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}
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// it's a flag. does it have an argument?
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f.args = f.args[1:]
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has_value := false
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value := ""
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for i := 1; i < len(name); i++ { // equals cannot be first
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if name[i] == '=' {
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value = name[i+1:]
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has_value = true
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name = name[0:i]
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break
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}
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}
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m := flags.formal
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flag, alreadythere := m[name] // BUG
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if !alreadythere {
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failf("flag provided but not defined: -%s\n", name)
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}
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if fv, ok := flag.Value.(*boolValue); ok { // special case: doesn't need an arg
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if has_value {
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if !fv.Set(value) {
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failf("invalid boolean value %q for flag: -%s\n", value, name)
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}
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} else {
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fv.Set("true")
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}
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} else {
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// It must have a value, which might be the next argument.
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if !has_value && len(f.args) > 0 {
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// value is the next arg
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has_value = true
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value, f.args = f.args[0], f.args[1:]
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}
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if !has_value {
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failf("flag needs an argument: -%s\n", name)
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}
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ok = flag.Value.Set(value)
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if !ok {
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failf("invalid value %q for flag: -%s\n", value, name)
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}
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}
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flags.actual[name] = flag
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return true
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}
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// Parse parses the command-line flags. Must be called after all flags are defined
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// and before any are accessed by the program.
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func Parse() {
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flags.args = os.Args[1:]
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for flags.parseOne() {
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}
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}
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func init() {
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flags = &allFlags{make(map[string]*Flag), make(map[string]*Flag), os.Args[1:]}
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}
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