1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 /* 6 Package flag implements command-line flag parsing. 7 8 Usage 9 10 Define flags using flag.String(), Bool(), Int(), etc. 11 12 This declares an integer flag, -flagname, stored in the pointer ip, with type *int. 13 import "flag" 14 var ip = flag.Int("flagname", 1234, "help message for flagname") 15 If you like, you can bind the flag to a variable using the Var() functions. 16 var flagvar int 17 func init() { 18 flag.IntVar(&flagvar, "flagname", 1234, "help message for flagname") 19 } 20 Or you can create custom flags that satisfy the Value interface (with 21 pointer receivers) and couple them to flag parsing by 22 flag.Var(&flagVal, "name", "help message for flagname") 23 For such flags, the default value is just the initial value of the variable. 24 25 After all flags are defined, call 26 flag.Parse() 27 to parse the command line into the defined flags. 28 29 Flags may then be used directly. If you're using the flags themselves, 30 they are all pointers; if you bind to variables, they're values. 31 fmt.Println("ip has value ", *ip) 32 fmt.Println("flagvar has value ", flagvar) 33 34 After parsing, the arguments following the flags are available as the 35 slice flag.Args() or individually as flag.Arg(i). 36 The arguments are indexed from 0 through flag.NArg()-1. 37 38 Command line flag syntax 39 40 The following forms are permitted: 41 42 -flag 43 -flag=x 44 -flag x // non-boolean flags only 45 One or two minus signs may be used; they are equivalent. 46 The last form is not permitted for boolean flags because the 47 meaning of the command 48 cmd -x * 49 where * is a Unix shell wildcard, will change if there is a file 50 called 0, false, etc. You must use the -flag=false form to turn 51 off a boolean flag. 52 53 Flag parsing stops just before the first non-flag argument 54 ("-" is a non-flag argument) or after the terminator "--". 55 56 Integer flags accept 1234, 0664, 0x1234 and may be negative. 57 Boolean flags may be: 58 1, 0, t, f, T, F, true, false, TRUE, FALSE, True, False 59 Duration flags accept any input valid for time.ParseDuration. 60 61 The default set of command-line flags is controlled by 62 top-level functions. The FlagSet type allows one to define 63 independent sets of flags, such as to implement subcommands 64 in a command-line interface. The methods of FlagSet are 65 analogous to the top-level functions for the command-line 66 flag set. 67 */ 68 package flag 69 70 import ( 71 "errors" 72 "fmt" 73 "io" 74 "os" 75 "reflect" 76 "sort" 77 "strconv" 78 "strings" 79 "time" 80 ) 81 82 // ErrHelp is the error returned if the -help or -h flag is invoked 83 // but no such flag is defined. 84 var ErrHelp = errors.New("flag: help requested") 85 86 // errParse is returned by Set if a flag's value fails to parse, such as with an invalid integer for Int. 87 // It then gets wrapped through failf to provide more information. 88 var errParse = errors.New("parse error") 89 90 // errRange is returned by Set if a flag's value is out of range. 91 // It then gets wrapped through failf to provide more information. 92 var errRange = errors.New("value out of range") 93 94 func numError(err error) error { 95 ne, ok := err.(*strconv.NumError) 96 if !ok { 97 return err 98 } 99 if ne.Err == strconv.ErrSyntax { 100 return errParse 101 } 102 if ne.Err == strconv.ErrRange { 103 return errRange 104 } 105 return err 106 } 107 108 // -- bool Value 109 type boolValue bool 110 111 func newBoolValue(val bool, p *bool) *boolValue { 112 *p = val 113 return (*boolValue)(p) 114 } 115 116 func (b *boolValue) Set(s string) error { 117 v, err := strconv.ParseBool(s) 118 if err != nil { 119 err = errParse 120 } 121 *b = boolValue(v) 122 return err 123 } 124 125 func (b *boolValue) Get() interface{} { return bool(*b) } 126 127 func (b *boolValue) String() string { return strconv.FormatBool(bool(*b)) } 128 129 func (b *boolValue) IsBoolFlag() bool { return true } 130 131 // optional interface to indicate boolean flags that can be 132 // supplied without "=value" text 133 type boolFlag interface { 134 Value 135 IsBoolFlag() bool 136 } 137 138 // -- int Value 139 type intValue int 140 141 func newIntValue(val int, p *int) *intValue { 142 *p = val 143 return (*intValue)(p) 144 } 145 146 func (i *intValue) Set(s string) error { 147 v, err := strconv.ParseInt(s, 0, strconv.IntSize) 148 if err != nil { 149 err = numError(err) 150 } 151 *i = intValue(v) 152 return err 153 } 154 155 func (i *intValue) Get() interface{} { return int(*i) } 156 157 func (i *intValue) String() string { return strconv.Itoa(int(*i)) } 158 159 // -- int64 Value 160 type int64Value int64 161 162 func newInt64Value(val int64, p *int64) *int64Value { 163 *p = val 164 return (*int64Value)(p) 165 } 166 167 func (i *int64Value) Set(s string) error { 168 v, err := strconv.ParseInt(s, 0, 64) 169 if err != nil { 170 err = numError(err) 171 } 172 *i = int64Value(v) 173 return err 174 } 175 176 func (i *int64Value) Get() interface{} { return int64(*i) } 177 178 func (i *int64Value) String() string { return strconv.FormatInt(int64(*i), 10) } 179 180 // -- uint Value 181 type uintValue uint 182 183 func newUintValue(val uint, p *uint) *uintValue { 184 *p = val 185 return (*uintValue)(p) 186 } 187 188 func (i *uintValue) Set(s string) error { 189 v, err := strconv.ParseUint(s, 0, strconv.IntSize) 190 if err != nil { 191 err = numError(err) 192 } 193 *i = uintValue(v) 194 return err 195 } 196 197 func (i *uintValue) Get() interface{} { return uint(*i) } 198 199 func (i *uintValue) String() string { return strconv.FormatUint(uint64(*i), 10) } 200 201 // -- uint64 Value 202 type uint64Value uint64 203 204 func newUint64Value(val uint64, p *uint64) *uint64Value { 205 *p = val 206 return (*uint64Value)(p) 207 } 208 209 func (i *uint64Value) Set(s string) error { 210 v, err := strconv.ParseUint(s, 0, 64) 211 if err != nil { 212 err = numError(err) 213 } 214 *i = uint64Value(v) 215 return err 216 } 217 218 func (i *uint64Value) Get() interface{} { return uint64(*i) } 219 220 func (i *uint64Value) String() string { return strconv.FormatUint(uint64(*i), 10) } 221 222 // -- string Value 223 type stringValue string 224 225 func newStringValue(val string, p *string) *stringValue { 226 *p = val 227 return (*stringValue)(p) 228 } 229 230 func (s *stringValue) Set(val string) error { 231 *s = stringValue(val) 232 return nil 233 } 234 235 func (s *stringValue) Get() interface{} { return string(*s) } 236 237 func (s *stringValue) String() string { return string(*s) } 238 239 // -- float64 Value 240 type float64Value float64 241 242 func newFloat64Value(val float64, p *float64) *float64Value { 243 *p = val 244 return (*float64Value)(p) 245 } 246 247 func (f *float64Value) Set(s string) error { 248 v, err := strconv.ParseFloat(s, 64) 249 if err != nil { 250 err = numError(err) 251 } 252 *f = float64Value(v) 253 return err 254 } 255 256 func (f *float64Value) Get() interface{} { return float64(*f) } 257 258 func (f *float64Value) String() string { return strconv.FormatFloat(float64(*f), 'g', -1, 64) } 259 260 // -- time.Duration Value 261 type durationValue time.Duration 262 263 func newDurationValue(val time.Duration, p *time.Duration) *durationValue { 264 *p = val 265 return (*durationValue)(p) 266 } 267 268 func (d *durationValue) Set(s string) error { 269 v, err := time.ParseDuration(s) 270 if err != nil { 271 err = errParse 272 } 273 *d = durationValue(v) 274 return err 275 } 276 277 func (d *durationValue) Get() interface{} { return time.Duration(*d) } 278 279 func (d *durationValue) String() string { return (*time.Duration)(d).String() } 280 281 // Value is the interface to the dynamic value stored in a flag. 282 // (The default value is represented as a string.) 283 // 284 // If a Value has an IsBoolFlag() bool method returning true, 285 // the command-line parser makes -name equivalent to -name=true 286 // rather than using the next command-line argument. 287 // 288 // Set is called once, in command line order, for each flag present. 289 // The flag package may call the String method with a zero-valued receiver, 290 // such as a nil pointer. 291 type Value interface { 292 String() string 293 Set(string) error 294 } 295 296 // Getter is an interface that allows the contents of a Value to be retrieved. 297 // It wraps the Value interface, rather than being part of it, because it 298 // appeared after Go 1 and its compatibility rules. All Value types provided 299 // by this package satisfy the Getter interface. 300 type Getter interface { 301 Value 302 Get() interface{} 303 } 304 305 // ErrorHandling defines how FlagSet.Parse behaves if the parse fails. 306 type ErrorHandling int 307 308 // These constants cause FlagSet.Parse to behave as described if the parse fails. 309 const ( 310 ContinueOnError ErrorHandling = iota // Return a descriptive error. 311 ExitOnError // Call os.Exit(2). 312 PanicOnError // Call panic with a descriptive error. 313 ) 314 315 // A FlagSet represents a set of defined flags. The zero value of a FlagSet 316 // has no name and has ContinueOnError error handling. 317 type FlagSet struct { 318 // Usage is the function called when an error occurs while parsing flags. 319 // The field is a function (not a method) that may be changed to point to 320 // a custom error handler. What happens after Usage is called depends 321 // on the ErrorHandling setting; for the command line, this defaults 322 // to ExitOnError, which exits the program after calling Usage. 323 Usage func() 324 325 name string 326 parsed bool 327 actual map[string]*Flag 328 formal map[string]*Flag 329 args []string // arguments after flags 330 errorHandling ErrorHandling 331 output io.Writer // nil means stderr; use out() accessor 332 } 333 334 // A Flag represents the state of a flag. 335 type Flag struct { 336 Name string // name as it appears on command line 337 Usage string // help message 338 Value Value // value as set 339 DefValue string // default value (as text); for usage message 340 } 341 342 // sortFlags returns the flags as a slice in lexicographical sorted order. 343 func sortFlags(flags map[string]*Flag) []*Flag { 344 result := make([]*Flag, len(flags)) 345 i := 0 346 for _, f := range flags { 347 result[i] = f 348 i++ 349 } 350 sort.Slice(result, func(i, j int) bool { 351 return result[i].Name < result[j].Name 352 }) 353 return result 354 } 355 356 // Output returns the destination for usage and error messages. os.Stderr is returned if 357 // output was not set or was set to nil. 358 func (f *FlagSet) Output() io.Writer { 359 if f.output == nil { 360 return os.Stderr 361 } 362 return f.output 363 } 364 365 // Name returns the name of the flag set. 366 func (f *FlagSet) Name() string { 367 return f.name 368 } 369 370 // ErrorHandling returns the error handling behavior of the flag set. 371 func (f *FlagSet) ErrorHandling() ErrorHandling { 372 return f.errorHandling 373 } 374 375 // SetOutput sets the destination for usage and error messages. 376 // If output is nil, os.Stderr is used. 377 func (f *FlagSet) SetOutput(output io.Writer) { 378 f.output = output 379 } 380 381 // VisitAll visits the flags in lexicographical order, calling fn for each. 382 // It visits all flags, even those not set. 383 func (f *FlagSet) VisitAll(fn func(*Flag)) { 384 for _, flag := range sortFlags(f.formal) { 385 fn(flag) 386 } 387 } 388 389 // VisitAll visits the command-line flags in lexicographical order, calling 390 // fn for each. It visits all flags, even those not set. 391 func VisitAll(fn func(*Flag)) { 392 CommandLine.VisitAll(fn) 393 } 394 395 // Visit visits the flags in lexicographical order, calling fn for each. 396 // It visits only those flags that have been set. 397 func (f *FlagSet) Visit(fn func(*Flag)) { 398 for _, flag := range sortFlags(f.actual) { 399 fn(flag) 400 } 401 } 402 403 // Visit visits the command-line flags in lexicographical order, calling fn 404 // for each. It visits only those flags that have been set. 405 func Visit(fn func(*Flag)) { 406 CommandLine.Visit(fn) 407 } 408 409 // Lookup returns the Flag structure of the named flag, returning nil if none exists. 410 func (f *FlagSet) Lookup(name string) *Flag { 411 return f.formal[name] 412 } 413 414 // Lookup returns the Flag structure of the named command-line flag, 415 // returning nil if none exists. 416 func Lookup(name string) *Flag { 417 return CommandLine.formal[name] 418 } 419 420 // Set sets the value of the named flag. 421 func (f *FlagSet) Set(name, value string) error { 422 flag, ok := f.formal[name] 423 if !ok { 424 return fmt.Errorf("no such flag -%v", name) 425 } 426 err := flag.Value.Set(value) 427 if err != nil { 428 return err 429 } 430 if f.actual == nil { 431 f.actual = make(map[string]*Flag) 432 } 433 f.actual[name] = flag 434 return nil 435 } 436 437 // Set sets the value of the named command-line flag. 438 func Set(name, value string) error { 439 return CommandLine.Set(name, value) 440 } 441 442 // isZeroValue determines whether the string represents the zero 443 // value for a flag. 444 func isZeroValue(flag *Flag, value string) bool { 445 // Build a zero value of the flag's Value type, and see if the 446 // result of calling its String method equals the value passed in. 447 // This works unless the Value type is itself an interface type. 448 typ := reflect.TypeOf(flag.Value) 449 var z reflect.Value 450 if typ.Kind() == reflect.Ptr { 451 z = reflect.New(typ.Elem()) 452 } else { 453 z = reflect.Zero(typ) 454 } 455 return value == z.Interface().(Value).String() 456 } 457 458 // UnquoteUsage extracts a back-quoted name from the usage 459 // string for a flag and returns it and the un-quoted usage. 460 // Given "a `name` to show" it returns ("name", "a name to show"). 461 // If there are no back quotes, the name is an educated guess of the 462 // type of the flag's value, or the empty string if the flag is boolean. 463 func UnquoteUsage(flag *Flag) (name string, usage string) { 464 // Look for a back-quoted name, but avoid the strings package. 465 usage = flag.Usage 466 for i := 0; i < len(usage); i++ { 467 if usage[i] == '`' { 468 for j := i + 1; j < len(usage); j++ { 469 if usage[j] == '`' { 470 name = usage[i+1 : j] 471 usage = usage[:i] + name + usage[j+1:] 472 return name, usage 473 } 474 } 475 break // Only one back quote; use type name. 476 } 477 } 478 // No explicit name, so use type if we can find one. 479 name = "value" 480 switch flag.Value.(type) { 481 case boolFlag: 482 name = "" 483 case *durationValue: 484 name = "duration" 485 case *float64Value: 486 name = "float" 487 case *intValue, *int64Value: 488 name = "int" 489 case *stringValue: 490 name = "string" 491 case *uintValue, *uint64Value: 492 name = "uint" 493 } 494 return 495 } 496 497 // PrintDefaults prints, to standard error unless configured otherwise, the 498 // default values of all defined command-line flags in the set. See the 499 // documentation for the global function PrintDefaults for more information. 500 func (f *FlagSet) PrintDefaults() { 501 f.VisitAll(func(flag *Flag) { 502 s := fmt.Sprintf(" -%s", flag.Name) // Two spaces before -; see next two comments. 503 name, usage := UnquoteUsage(flag) 504 if len(name) > 0 { 505 s += " " + name 506 } 507 // Boolean flags of one ASCII letter are so common we 508 // treat them specially, putting their usage on the same line. 509 if len(s) <= 4 { // space, space, '-', 'x'. 510 s += "\t" 511 } else { 512 // Four spaces before the tab triggers good alignment 513 // for both 4- and 8-space tab stops. 514 s += "\n \t" 515 } 516 s += strings.ReplaceAll(usage, "\n", "\n \t") 517 518 if !isZeroValue(flag, flag.DefValue) { 519 if _, ok := flag.Value.(*stringValue); ok { 520 // put quotes on the value 521 s += fmt.Sprintf(" (default %q)", flag.DefValue) 522 } else { 523 s += fmt.Sprintf(" (default %v)", flag.DefValue) 524 } 525 } 526 fmt.Fprint(f.Output(), s, "\n") 527 }) 528 } 529 530 // PrintDefaults prints, to standard error unless configured otherwise, 531 // a usage message showing the default settings of all defined 532 // command-line flags. 533 // For an integer valued flag x, the default output has the form 534 // -x int 535 // usage-message-for-x (default 7) 536 // The usage message will appear on a separate line for anything but 537 // a bool flag with a one-byte name. For bool flags, the type is 538 // omitted and if the flag name is one byte the usage message appears 539 // on the same line. The parenthetical default is omitted if the 540 // default is the zero value for the type. The listed type, here int, 541 // can be changed by placing a back-quoted name in the flag's usage 542 // string; the first such item in the message is taken to be a parameter 543 // name to show in the message and the back quotes are stripped from 544 // the message when displayed. For instance, given 545 // flag.String("I", "", "search `directory` for include files") 546 // the output will be 547 // -I directory 548 // search directory for include files. 549 // 550 // To change the destination for flag messages, call CommandLine.SetOutput. 551 func PrintDefaults() { 552 CommandLine.PrintDefaults() 553 } 554 555 // defaultUsage is the default function to print a usage message. 556 func (f *FlagSet) defaultUsage() { 557 if f.name == "" { 558 fmt.Fprintf(f.Output(), "Usage:\n") 559 } else { 560 fmt.Fprintf(f.Output(), "Usage of %s:\n", f.name) 561 } 562 f.PrintDefaults() 563 } 564 565 // NOTE: Usage is not just defaultUsage(CommandLine) 566 // because it serves (via godoc flag Usage) as the example 567 // for how to write your own usage function. 568 569 // Usage prints a usage message documenting all defined command-line flags 570 // to CommandLine's output, which by default is os.Stderr. 571 // It is called when an error occurs while parsing flags. 572 // The function is a variable that may be changed to point to a custom function. 573 // By default it prints a simple header and calls PrintDefaults; for details about the 574 // format of the output and how to control it, see the documentation for PrintDefaults. 575 // Custom usage functions may choose to exit the program; by default exiting 576 // happens anyway as the command line's error handling strategy is set to 577 // ExitOnError. 578 var Usage = func() { 579 fmt.Fprintf(CommandLine.Output(), "Usage of %s:\n", os.Args[0]) 580 PrintDefaults() 581 } 582 583 // NFlag returns the number of flags that have been set. 584 func (f *FlagSet) NFlag() int { return len(f.actual) } 585 586 // NFlag returns the number of command-line flags that have been set. 587 func NFlag() int { return len(CommandLine.actual) } 588 589 // Arg returns the i'th argument. Arg(0) is the first remaining argument 590 // after flags have been processed. Arg returns an empty string if the 591 // requested element does not exist. 592 func (f *FlagSet) Arg(i int) string { 593 if i < 0 || i >= len(f.args) { 594 return "" 595 } 596 return f.args[i] 597 } 598 599 // Arg returns the i'th command-line argument. Arg(0) is the first remaining argument 600 // after flags have been processed. Arg returns an empty string if the 601 // requested element does not exist. 602 func Arg(i int) string { 603 return CommandLine.Arg(i) 604 } 605 606 // NArg is the number of arguments remaining after flags have been processed. 607 func (f *FlagSet) NArg() int { return len(f.args) } 608 609 // NArg is the number of arguments remaining after flags have been processed. 610 func NArg() int { return len(CommandLine.args) } 611 612 // Args returns the non-flag arguments. 613 func (f *FlagSet) Args() []string { return f.args } 614 615 // Args returns the non-flag command-line arguments. 616 func Args() []string { return CommandLine.args } 617 618 // BoolVar defines a bool flag with specified name, default value, and usage string. 619 // The argument p points to a bool variable in which to store the value of the flag. 620 func (f *FlagSet) BoolVar(p *bool, name string, value bool, usage string) { 621 f.Var(newBoolValue(value, p), name, usage) 622 } 623 624 // BoolVar defines a bool flag with specified name, default value, and usage string. 625 // The argument p points to a bool variable in which to store the value of the flag. 626 func BoolVar(p *bool, name string, value bool, usage string) { 627 CommandLine.Var(newBoolValue(value, p), name, usage) 628 } 629 630 // Bool defines a bool flag with specified name, default value, and usage string. 631 // The return value is the address of a bool variable that stores the value of the flag. 632 func (f *FlagSet) Bool(name string, value bool, usage string) *bool { 633 p := new(bool) 634 f.BoolVar(p, name, value, usage) 635 return p 636 } 637 638 // Bool defines a bool flag with specified name, default value, and usage string. 639 // The return value is the address of a bool variable that stores the value of the flag. 640 func Bool(name string, value bool, usage string) *bool { 641 return CommandLine.Bool(name, value, usage) 642 } 643 644 // IntVar defines an int flag with specified name, default value, and usage string. 645 // The argument p points to an int variable in which to store the value of the flag. 646 func (f *FlagSet) IntVar(p *int, name string, value int, usage string) { 647 f.Var(newIntValue(value, p), name, usage) 648 } 649 650 // IntVar defines an int flag with specified name, default value, and usage string. 651 // The argument p points to an int variable in which to store the value of the flag. 652 func IntVar(p *int, name string, value int, usage string) { 653 CommandLine.Var(newIntValue(value, p), name, usage) 654 } 655 656 // Int defines an int flag with specified name, default value, and usage string. 657 // The return value is the address of an int variable that stores the value of the flag. 658 func (f *FlagSet) Int(name string, value int, usage string) *int { 659 p := new(int) 660 f.IntVar(p, name, value, usage) 661 return p 662 } 663 664 // Int defines an int flag with specified name, default value, and usage string. 665 // The return value is the address of an int variable that stores the value of the flag. 666 func Int(name string, value int, usage string) *int { 667 return CommandLine.Int(name, value, usage) 668 } 669 670 // Int64Var defines an int64 flag with specified name, default value, and usage string. 671 // The argument p points to an int64 variable in which to store the value of the flag. 672 func (f *FlagSet) Int64Var(p *int64, name string, value int64, usage string) { 673 f.Var(newInt64Value(value, p), name, usage) 674 } 675 676 // Int64Var defines an int64 flag with specified name, default value, and usage string. 677 // The argument p points to an int64 variable in which to store the value of the flag. 678 func Int64Var(p *int64, name string, value int64, usage string) { 679 CommandLine.Var(newInt64Value(value, p), name, usage) 680 } 681 682 // Int64 defines an int64 flag with specified name, default value, and usage string. 683 // The return value is the address of an int64 variable that stores the value of the flag. 684 func (f *FlagSet) Int64(name string, value int64, usage string) *int64 { 685 p := new(int64) 686 f.Int64Var(p, name, value, usage) 687 return p 688 } 689 690 // Int64 defines an int64 flag with specified name, default value, and usage string. 691 // The return value is the address of an int64 variable that stores the value of the flag. 692 func Int64(name string, value int64, usage string) *int64 { 693 return CommandLine.Int64(name, value, usage) 694 } 695 696 // UintVar defines a uint flag with specified name, default value, and usage string. 697 // The argument p points to a uint variable in which to store the value of the flag. 698 func (f *FlagSet) UintVar(p *uint, name string, value uint, usage string) { 699 f.Var(newUintValue(value, p), name, usage) 700 } 701 702 // UintVar defines a uint flag with specified name, default value, and usage string. 703 // The argument p points to a uint variable in which to store the value of the flag. 704 func UintVar(p *uint, name string, value uint, usage string) { 705 CommandLine.Var(newUintValue(value, p), name, usage) 706 } 707 708 // Uint defines a uint flag with specified name, default value, and usage string. 709 // The return value is the address of a uint variable that stores the value of the flag. 710 func (f *FlagSet) Uint(name string, value uint, usage string) *uint { 711 p := new(uint) 712 f.UintVar(p, name, value, usage) 713 return p 714 } 715 716 // Uint defines a uint flag with specified name, default value, and usage string. 717 // The return value is the address of a uint variable that stores the value of the flag. 718 func Uint(name string, value uint, usage string) *uint { 719 return CommandLine.Uint(name, value, usage) 720 } 721 722 // Uint64Var defines a uint64 flag with specified name, default value, and usage string. 723 // The argument p points to a uint64 variable in which to store the value of the flag. 724 func (f *FlagSet) Uint64Var(p *uint64, name string, value uint64, usage string) { 725 f.Var(newUint64Value(value, p), name, usage) 726 } 727 728 // Uint64Var defines a uint64 flag with specified name, default value, and usage string. 729 // The argument p points to a uint64 variable in which to store the value of the flag. 730 func Uint64Var(p *uint64, name string, value uint64, usage string) { 731 CommandLine.Var(newUint64Value(value, p), name, usage) 732 } 733 734 // Uint64 defines a uint64 flag with specified name, default value, and usage string. 735 // The return value is the address of a uint64 variable that stores the value of the flag. 736 func (f *FlagSet) Uint64(name string, value uint64, usage string) *uint64 { 737 p := new(uint64) 738 f.Uint64Var(p, name, value, usage) 739 return p 740 } 741 742 // Uint64 defines a uint64 flag with specified name, default value, and usage string. 743 // The return value is the address of a uint64 variable that stores the value of the flag. 744 func Uint64(name string, value uint64, usage string) *uint64 { 745 return CommandLine.Uint64(name, value, usage) 746 } 747 748 // StringVar defines a string flag with specified name, default value, and usage string. 749 // The argument p points to a string variable in which to store the value of the flag. 750 func (f *FlagSet) StringVar(p *string, name string, value string, usage string) { 751 f.Var(newStringValue(value, p), name, usage) 752 } 753 754 // StringVar defines a string flag with specified name, default value, and usage string. 755 // The argument p points to a string variable in which to store the value of the flag. 756 func StringVar(p *string, name string, value string, usage string) { 757 CommandLine.Var(newStringValue(value, p), name, usage) 758 } 759 760 // String defines a string flag with specified name, default value, and usage string. 761 // The return value is the address of a string variable that stores the value of the flag. 762 func (f *FlagSet) String(name string, value string, usage string) *string { 763 p := new(string) 764 f.StringVar(p, name, value, usage) 765 return p 766 } 767 768 // String defines a string flag with specified name, default value, and usage string. 769 // The return value is the address of a string variable that stores the value of the flag. 770 func String(name string, value string, usage string) *string { 771 return CommandLine.String(name, value, usage) 772 } 773 774 // Float64Var defines a float64 flag with specified name, default value, and usage string. 775 // The argument p points to a float64 variable in which to store the value of the flag. 776 func (f *FlagSet) Float64Var(p *float64, name string, value float64, usage string) { 777 f.Var(newFloat64Value(value, p), name, usage) 778 } 779 780 // Float64Var defines a float64 flag with specified name, default value, and usage string. 781 // The argument p points to a float64 variable in which to store the value of the flag. 782 func Float64Var(p *float64, name string, value float64, usage string) { 783 CommandLine.Var(newFloat64Value(value, p), name, usage) 784 } 785 786 // Float64 defines a float64 flag with specified name, default value, and usage string. 787 // The return value is the address of a float64 variable that stores the value of the flag. 788 func (f *FlagSet) Float64(name string, value float64, usage string) *float64 { 789 p := new(float64) 790 f.Float64Var(p, name, value, usage) 791 return p 792 } 793 794 // Float64 defines a float64 flag with specified name, default value, and usage string. 795 // The return value is the address of a float64 variable that stores the value of the flag. 796 func Float64(name string, value float64, usage string) *float64 { 797 return CommandLine.Float64(name, value, usage) 798 } 799 800 // DurationVar defines a time.Duration flag with specified name, default value, and usage string. 801 // The argument p points to a time.Duration variable in which to store the value of the flag. 802 // The flag accepts a value acceptable to time.ParseDuration. 803 func (f *FlagSet) DurationVar(p *time.Duration, name string, value time.Duration, usage string) { 804 f.Var(newDurationValue(value, p), name, usage) 805 } 806 807 // DurationVar defines a time.Duration flag with specified name, default value, and usage string. 808 // The argument p points to a time.Duration variable in which to store the value of the flag. 809 // The flag accepts a value acceptable to time.ParseDuration. 810 func DurationVar(p *time.Duration, name string, value time.Duration, usage string) { 811 CommandLine.Var(newDurationValue(value, p), name, usage) 812 } 813 814 // Duration defines a time.Duration flag with specified name, default value, and usage string. 815 // The return value is the address of a time.Duration variable that stores the value of the flag. 816 // The flag accepts a value acceptable to time.ParseDuration. 817 func (f *FlagSet) Duration(name string, value time.Duration, usage string) *time.Duration { 818 p := new(time.Duration) 819 f.DurationVar(p, name, value, usage) 820 return p 821 } 822 823 // Duration defines a time.Duration flag with specified name, default value, and usage string. 824 // The return value is the address of a time.Duration variable that stores the value of the flag. 825 // The flag accepts a value acceptable to time.ParseDuration. 826 func Duration(name string, value time.Duration, usage string) *time.Duration { 827 return CommandLine.Duration(name, value, usage) 828 } 829 830 // Var defines a flag with the specified name and usage string. The type and 831 // value of the flag are represented by the first argument, of type Value, which 832 // typically holds a user-defined implementation of Value. For instance, the 833 // caller could create a flag that turns a comma-separated string into a slice 834 // of strings by giving the slice the methods of Value; in particular, Set would 835 // decompose the comma-separated string into the slice. 836 func (f *FlagSet) Var(value Value, name string, usage string) { 837 // Remember the default value as a string; it won't change. 838 flag := &Flag{name, usage, value, value.String()} 839 _, alreadythere := f.formal[name] 840 if alreadythere { 841 var msg string 842 if f.name == "" { 843 msg = fmt.Sprintf("flag redefined: %s", name) 844 } else { 845 msg = fmt.Sprintf("%s flag redefined: %s", f.name, name) 846 } 847 fmt.Fprintln(f.Output(), msg) 848 panic(msg) // Happens only if flags are declared with identical names 849 } 850 if f.formal == nil { 851 f.formal = make(map[string]*Flag) 852 } 853 f.formal[name] = flag 854 } 855 856 // Var defines a flag with the specified name and usage string. The type and 857 // value of the flag are represented by the first argument, of type Value, which 858 // typically holds a user-defined implementation of Value. For instance, the 859 // caller could create a flag that turns a comma-separated string into a slice 860 // of strings by giving the slice the methods of Value; in particular, Set would 861 // decompose the comma-separated string into the slice. 862 func Var(value Value, name string, usage string) { 863 CommandLine.Var(value, name, usage) 864 } 865 866 // failf prints to standard error a formatted error and usage message and 867 // returns the error. 868 func (f *FlagSet) failf(format string, a ...interface{}) error { 869 err := fmt.Errorf(format, a...) 870 fmt.Fprintln(f.Output(), err) 871 f.usage() 872 return err 873 } 874 875 // usage calls the Usage method for the flag set if one is specified, 876 // or the appropriate default usage function otherwise. 877 func (f *FlagSet) usage() { 878 if f.Usage == nil { 879 f.defaultUsage() 880 } else { 881 f.Usage() 882 } 883 } 884 885 // parseOne parses one flag. It reports whether a flag was seen. 886 func (f *FlagSet) parseOne() (bool, error) { 887 if len(f.args) == 0 { 888 return false, nil 889 } 890 s := f.args[0] 891 if len(s) < 2 || s[0] != '-' { 892 return false, nil 893 } 894 numMinuses := 1 895 if s[1] == '-' { 896 numMinuses++ 897 if len(s) == 2 { // "--" terminates the flags 898 f.args = f.args[1:] 899 return false, nil 900 } 901 } 902 name := s[numMinuses:] 903 if len(name) == 0 || name[0] == '-' || name[0] == '=' { 904 return false, f.failf("bad flag syntax: %s", s) 905 } 906 907 // it's a flag. does it have an argument? 908 f.args = f.args[1:] 909 hasValue := false 910 value := "" 911 for i := 1; i < len(name); i++ { // equals cannot be first 912 if name[i] == '=' { 913 value = name[i+1:] 914 hasValue = true 915 name = name[0:i] 916 break 917 } 918 } 919 m := f.formal 920 flag, alreadythere := m[name] // BUG 921 if !alreadythere { 922 if name == "help" || name == "h" { // special case for nice help message. 923 f.usage() 924 return false, ErrHelp 925 } 926 return false, f.failf("flag provided but not defined: -%s", name) 927 } 928 929 if fv, ok := flag.Value.(boolFlag); ok && fv.IsBoolFlag() { // special case: doesn't need an arg 930 if hasValue { 931 if err := fv.Set(value); err != nil { 932 return false, f.failf("invalid boolean value %q for -%s: %v", value, name, err) 933 } 934 } else { 935 if err := fv.Set("true"); err != nil { 936 return false, f.failf("invalid boolean flag %s: %v", name, err) 937 } 938 } 939 } else { 940 // It must have a value, which might be the next argument. 941 if !hasValue && len(f.args) > 0 { 942 // value is the next arg 943 hasValue = true 944 value, f.args = f.args[0], f.args[1:] 945 } 946 if !hasValue { 947 return false, f.failf("flag needs an argument: -%s", name) 948 } 949 if err := flag.Value.Set(value); err != nil { 950 return false, f.failf("invalid value %q for flag -%s: %v", value, name, err) 951 } 952 } 953 if f.actual == nil { 954 f.actual = make(map[string]*Flag) 955 } 956 f.actual[name] = flag 957 return true, nil 958 } 959 960 // Parse parses flag definitions from the argument list, which should not 961 // include the command name. Must be called after all flags in the FlagSet 962 // are defined and before flags are accessed by the program. 963 // The return value will be ErrHelp if -help or -h were set but not defined. 964 func (f *FlagSet) Parse(arguments []string) error { 965 f.parsed = true 966 f.args = arguments 967 for { 968 seen, err := f.parseOne() 969 if seen { 970 continue 971 } 972 if err == nil { 973 break 974 } 975 switch f.errorHandling { 976 case ContinueOnError: 977 return err 978 case ExitOnError: 979 os.Exit(2) 980 case PanicOnError: 981 panic(err) 982 } 983 } 984 return nil 985 } 986 987 // Parsed reports whether f.Parse has been called. 988 func (f *FlagSet) Parsed() bool { 989 return f.parsed 990 } 991 992 // Parse parses the command-line flags from os.Args[1:]. Must be called 993 // after all flags are defined and before flags are accessed by the program. 994 func Parse() { 995 // Ignore errors; CommandLine is set for ExitOnError. 996 CommandLine.Parse(os.Args[1:]) 997 } 998 999 // Parsed reports whether the command-line flags have been parsed. 1000 func Parsed() bool { 1001 return CommandLine.Parsed() 1002 } 1003 1004 // CommandLine is the default set of command-line flags, parsed from os.Args. 1005 // The top-level functions such as BoolVar, Arg, and so on are wrappers for the 1006 // methods of CommandLine. 1007 var CommandLine = NewFlagSet(os.Args[0], ExitOnError) 1008 1009 func init() { 1010 // Override generic FlagSet default Usage with call to global Usage. 1011 // Note: This is not CommandLine.Usage = Usage, 1012 // because we want any eventual call to use any updated value of Usage, 1013 // not the value it has when this line is run. 1014 CommandLine.Usage = commandLineUsage 1015 } 1016 1017 func commandLineUsage() { 1018 Usage() 1019 } 1020 1021 // NewFlagSet returns a new, empty flag set with the specified name and 1022 // error handling property. If the name is not empty, it will be printed 1023 // in the default usage message and in error messages. 1024 func NewFlagSet(name string, errorHandling ErrorHandling) *FlagSet { 1025 f := &FlagSet{ 1026 name: name, 1027 errorHandling: errorHandling, 1028 } 1029 f.Usage = f.defaultUsage 1030 return f 1031 } 1032 1033 // Init sets the name and error handling property for a flag set. 1034 // By default, the zero FlagSet uses an empty name and the 1035 // ContinueOnError error handling policy. 1036 func (f *FlagSet) Init(name string, errorHandling ErrorHandling) { 1037 f.name = name 1038 f.errorHandling = errorHandling 1039 } 1040