Source file src/flag/flag.go
Documentation: flag
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, -n, stored in the pointer nFlag, with type *int: 13 import "flag" 14 var nFlag = flag.Int("n", 1234, "help message for flag n") 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 type funcValue func(string) error 282 283 func (f funcValue) Set(s string) error { return f(s) } 284 285 func (f funcValue) String() string { return "" } 286 287 // Value is the interface to the dynamic value stored in a flag. 288 // (The default value is represented as a string.) 289 // 290 // If a Value has an IsBoolFlag() bool method returning true, 291 // the command-line parser makes -name equivalent to -name=true 292 // rather than using the next command-line argument. 293 // 294 // Set is called once, in command line order, for each flag present. 295 // The flag package may call the String method with a zero-valued receiver, 296 // such as a nil pointer. 297 type Value interface { 298 String() string 299 Set(string) error 300 } 301 302 // Getter is an interface that allows the contents of a Value to be retrieved. 303 // It wraps the Value interface, rather than being part of it, because it 304 // appeared after Go 1 and its compatibility rules. All Value types provided 305 // by this package satisfy the Getter interface, except the type used by Func. 306 type Getter interface { 307 Value 308 Get() interface{} 309 } 310 311 // ErrorHandling defines how FlagSet.Parse behaves if the parse fails. 312 type ErrorHandling int 313 314 // These constants cause FlagSet.Parse to behave as described if the parse fails. 315 const ( 316 ContinueOnError ErrorHandling = iota // Return a descriptive error. 317 ExitOnError // Call os.Exit(2) or for -h/-help Exit(0). 318 PanicOnError // Call panic with a descriptive error. 319 ) 320 321 // A FlagSet represents a set of defined flags. The zero value of a FlagSet 322 // has no name and has ContinueOnError error handling. 323 // 324 // Flag names must be unique within a FlagSet. An attempt to define a flag whose 325 // name is already in use will cause a panic. 326 type FlagSet struct { 327 // Usage is the function called when an error occurs while parsing flags. 328 // The field is a function (not a method) that may be changed to point to 329 // a custom error handler. What happens after Usage is called depends 330 // on the ErrorHandling setting; for the command line, this defaults 331 // to ExitOnError, which exits the program after calling Usage. 332 Usage func() 333 334 name string 335 parsed bool 336 actual map[string]*Flag 337 formal map[string]*Flag 338 args []string // arguments after flags 339 errorHandling ErrorHandling 340 output io.Writer // nil means stderr; use Output() accessor 341 } 342 343 // A Flag represents the state of a flag. 344 type Flag struct { 345 Name string // name as it appears on command line 346 Usage string // help message 347 Value Value // value as set 348 DefValue string // default value (as text); for usage message 349 } 350 351 // sortFlags returns the flags as a slice in lexicographical sorted order. 352 func sortFlags(flags map[string]*Flag) []*Flag { 353 result := make([]*Flag, len(flags)) 354 i := 0 355 for _, f := range flags { 356 result[i] = f 357 i++ 358 } 359 sort.Slice(result, func(i, j int) bool { 360 return result[i].Name < result[j].Name 361 }) 362 return result 363 } 364 365 // Output returns the destination for usage and error messages. os.Stderr is returned if 366 // output was not set or was set to nil. 367 func (f *FlagSet) Output() io.Writer { 368 if f.output == nil { 369 return os.Stderr 370 } 371 return f.output 372 } 373 374 // Name returns the name of the flag set. 375 func (f *FlagSet) Name() string { 376 return f.name 377 } 378 379 // ErrorHandling returns the error handling behavior of the flag set. 380 func (f *FlagSet) ErrorHandling() ErrorHandling { 381 return f.errorHandling 382 } 383 384 // SetOutput sets the destination for usage and error messages. 385 // If output is nil, os.Stderr is used. 386 func (f *FlagSet) SetOutput(output io.Writer) { 387 f.output = output 388 } 389 390 // VisitAll visits the flags in lexicographical order, calling fn for each. 391 // It visits all flags, even those not set. 392 func (f *FlagSet) VisitAll(fn func(*Flag)) { 393 for _, flag := range sortFlags(f.formal) { 394 fn(flag) 395 } 396 } 397 398 // VisitAll visits the command-line flags in lexicographical order, calling 399 // fn for each. It visits all flags, even those not set. 400 func VisitAll(fn func(*Flag)) { 401 CommandLine.VisitAll(fn) 402 } 403 404 // Visit visits the flags in lexicographical order, calling fn for each. 405 // It visits only those flags that have been set. 406 func (f *FlagSet) Visit(fn func(*Flag)) { 407 for _, flag := range sortFlags(f.actual) { 408 fn(flag) 409 } 410 } 411 412 // Visit visits the command-line flags in lexicographical order, calling fn 413 // for each. It visits only those flags that have been set. 414 func Visit(fn func(*Flag)) { 415 CommandLine.Visit(fn) 416 } 417 418 // Lookup returns the Flag structure of the named flag, returning nil if none exists. 419 func (f *FlagSet) Lookup(name string) *Flag { 420 return f.formal[name] 421 } 422 423 // Lookup returns the Flag structure of the named command-line flag, 424 // returning nil if none exists. 425 func Lookup(name string) *Flag { 426 return CommandLine.formal[name] 427 } 428 429 // Set sets the value of the named flag. 430 func (f *FlagSet) Set(name, value string) error { 431 flag, ok := f.formal[name] 432 if !ok { 433 return fmt.Errorf("no such flag -%v", name) 434 } 435 err := flag.Value.Set(value) 436 if err != nil { 437 return err 438 } 439 if f.actual == nil { 440 f.actual = make(map[string]*Flag) 441 } 442 f.actual[name] = flag 443 return nil 444 } 445 446 // Set sets the value of the named command-line flag. 447 func Set(name, value string) error { 448 return CommandLine.Set(name, value) 449 } 450 451 // isZeroValue determines whether the string represents the zero 452 // value for a flag. 453 func isZeroValue(flag *Flag, value string) bool { 454 // Build a zero value of the flag's Value type, and see if the 455 // result of calling its String method equals the value passed in. 456 // This works unless the Value type is itself an interface type. 457 typ := reflect.TypeOf(flag.Value) 458 var z reflect.Value 459 if typ.Kind() == reflect.Ptr { 460 z = reflect.New(typ.Elem()) 461 } else { 462 z = reflect.Zero(typ) 463 } 464 return value == z.Interface().(Value).String() 465 } 466 467 // UnquoteUsage extracts a back-quoted name from the usage 468 // string for a flag and returns it and the un-quoted usage. 469 // Given "a `name` to show" it returns ("name", "a name to show"). 470 // If there are no back quotes, the name is an educated guess of the 471 // type of the flag's value, or the empty string if the flag is boolean. 472 func UnquoteUsage(flag *Flag) (name string, usage string) { 473 // Look for a back-quoted name, but avoid the strings package. 474 usage = flag.Usage 475 for i := 0; i < len(usage); i++ { 476 if usage[i] == '`' { 477 for j := i + 1; j < len(usage); j++ { 478 if usage[j] == '`' { 479 name = usage[i+1 : j] 480 usage = usage[:i] + name + usage[j+1:] 481 return name, usage 482 } 483 } 484 break // Only one back quote; use type name. 485 } 486 } 487 // No explicit name, so use type if we can find one. 488 name = "value" 489 switch flag.Value.(type) { 490 case boolFlag: 491 name = "" 492 case *durationValue: 493 name = "duration" 494 case *float64Value: 495 name = "float" 496 case *intValue, *int64Value: 497 name = "int" 498 case *stringValue: 499 name = "string" 500 case *uintValue, *uint64Value: 501 name = "uint" 502 } 503 return 504 } 505 506 // PrintDefaults prints, to standard error unless configured otherwise, the 507 // default values of all defined command-line flags in the set. See the 508 // documentation for the global function PrintDefaults for more information. 509 func (f *FlagSet) PrintDefaults() { 510 f.VisitAll(func(flag *Flag) { 511 s := fmt.Sprintf(" -%s", flag.Name) // Two spaces before -; see next two comments. 512 name, usage := UnquoteUsage(flag) 513 if len(name) > 0 { 514 s += " " + name 515 } 516 // Boolean flags of one ASCII letter are so common we 517 // treat them specially, putting their usage on the same line. 518 if len(s) <= 4 { // space, space, '-', 'x'. 519 s += "\t" 520 } else { 521 // Four spaces before the tab triggers good alignment 522 // for both 4- and 8-space tab stops. 523 s += "\n \t" 524 } 525 s += strings.ReplaceAll(usage, "\n", "\n \t") 526 527 if !isZeroValue(flag, flag.DefValue) { 528 if _, ok := flag.Value.(*stringValue); ok { 529 // put quotes on the value 530 s += fmt.Sprintf(" (default %q)", flag.DefValue) 531 } else { 532 s += fmt.Sprintf(" (default %v)", flag.DefValue) 533 } 534 } 535 fmt.Fprint(f.Output(), s, "\n") 536 }) 537 } 538 539 // PrintDefaults prints, to standard error unless configured otherwise, 540 // a usage message showing the default settings of all defined 541 // command-line flags. 542 // For an integer valued flag x, the default output has the form 543 // -x int 544 // usage-message-for-x (default 7) 545 // The usage message will appear on a separate line for anything but 546 // a bool flag with a one-byte name. For bool flags, the type is 547 // omitted and if the flag name is one byte the usage message appears 548 // on the same line. The parenthetical default is omitted if the 549 // default is the zero value for the type. The listed type, here int, 550 // can be changed by placing a back-quoted name in the flag's usage 551 // string; the first such item in the message is taken to be a parameter 552 // name to show in the message and the back quotes are stripped from 553 // the message when displayed. For instance, given 554 // flag.String("I", "", "search `directory` for include files") 555 // the output will be 556 // -I directory 557 // search directory for include files. 558 // 559 // To change the destination for flag messages, call CommandLine.SetOutput. 560 func PrintDefaults() { 561 CommandLine.PrintDefaults() 562 } 563 564 // defaultUsage is the default function to print a usage message. 565 func (f *FlagSet) defaultUsage() { 566 if f.name == "" { 567 fmt.Fprintf(f.Output(), "Usage:\n") 568 } else { 569 fmt.Fprintf(f.Output(), "Usage of %s:\n", f.name) 570 } 571 f.PrintDefaults() 572 } 573 574 // NOTE: Usage is not just defaultUsage(CommandLine) 575 // because it serves (via godoc flag Usage) as the example 576 // for how to write your own usage function. 577 578 // Usage prints a usage message documenting all defined command-line flags 579 // to CommandLine's output, which by default is os.Stderr. 580 // It is called when an error occurs while parsing flags. 581 // The function is a variable that may be changed to point to a custom function. 582 // By default it prints a simple header and calls PrintDefaults; for details about the 583 // format of the output and how to control it, see the documentation for PrintDefaults. 584 // Custom usage functions may choose to exit the program; by default exiting 585 // happens anyway as the command line's error handling strategy is set to 586 // ExitOnError. 587 var Usage = func() { 588 fmt.Fprintf(CommandLine.Output(), "Usage of %s:\n", os.Args[0]) 589 PrintDefaults() 590 } 591 592 // NFlag returns the number of flags that have been set. 593 func (f *FlagSet) NFlag() int { return len(f.actual) } 594 595 // NFlag returns the number of command-line flags that have been set. 596 func NFlag() int { return len(CommandLine.actual) } 597 598 // Arg returns the i'th argument. Arg(0) is the first remaining argument 599 // after flags have been processed. Arg returns an empty string if the 600 // requested element does not exist. 601 func (f *FlagSet) Arg(i int) string { 602 if i < 0 || i >= len(f.args) { 603 return "" 604 } 605 return f.args[i] 606 } 607 608 // Arg returns the i'th command-line argument. Arg(0) is the first remaining argument 609 // after flags have been processed. Arg returns an empty string if the 610 // requested element does not exist. 611 func Arg(i int) string { 612 return CommandLine.Arg(i) 613 } 614 615 // NArg is the number of arguments remaining after flags have been processed. 616 func (f *FlagSet) NArg() int { return len(f.args) } 617 618 // NArg is the number of arguments remaining after flags have been processed. 619 func NArg() int { return len(CommandLine.args) } 620 621 // Args returns the non-flag arguments. 622 func (f *FlagSet) Args() []string { return f.args } 623 624 // Args returns the non-flag command-line arguments. 625 func Args() []string { return CommandLine.args } 626 627 // BoolVar defines a bool flag with specified name, default value, and usage string. 628 // The argument p points to a bool variable in which to store the value of the flag. 629 func (f *FlagSet) BoolVar(p *bool, name string, value bool, usage string) { 630 f.Var(newBoolValue(value, p), name, usage) 631 } 632 633 // BoolVar defines a bool flag with specified name, default value, and usage string. 634 // The argument p points to a bool variable in which to store the value of the flag. 635 func BoolVar(p *bool, name string, value bool, usage string) { 636 CommandLine.Var(newBoolValue(value, p), name, usage) 637 } 638 639 // Bool defines a bool flag with specified name, default value, and usage string. 640 // The return value is the address of a bool variable that stores the value of the flag. 641 func (f *FlagSet) Bool(name string, value bool, usage string) *bool { 642 p := new(bool) 643 f.BoolVar(p, name, value, usage) 644 return p 645 } 646 647 // Bool defines a bool flag with specified name, default value, and usage string. 648 // The return value is the address of a bool variable that stores the value of the flag. 649 func Bool(name string, value bool, usage string) *bool { 650 return CommandLine.Bool(name, value, usage) 651 } 652 653 // IntVar defines an int flag with specified name, default value, and usage string. 654 // The argument p points to an int variable in which to store the value of the flag. 655 func (f *FlagSet) IntVar(p *int, name string, value int, usage string) { 656 f.Var(newIntValue(value, p), name, usage) 657 } 658 659 // IntVar defines an int flag with specified name, default value, and usage string. 660 // The argument p points to an int variable in which to store the value of the flag. 661 func IntVar(p *int, name string, value int, usage string) { 662 CommandLine.Var(newIntValue(value, p), name, usage) 663 } 664 665 // Int defines an int flag with specified name, default value, and usage string. 666 // The return value is the address of an int variable that stores the value of the flag. 667 func (f *FlagSet) Int(name string, value int, usage string) *int { 668 p := new(int) 669 f.IntVar(p, name, value, usage) 670 return p 671 } 672 673 // Int defines an int flag with specified name, default value, and usage string. 674 // The return value is the address of an int variable that stores the value of the flag. 675 func Int(name string, value int, usage string) *int { 676 return CommandLine.Int(name, value, usage) 677 } 678 679 // Int64Var defines an int64 flag with specified name, default value, and usage string. 680 // The argument p points to an int64 variable in which to store the value of the flag. 681 func (f *FlagSet) Int64Var(p *int64, name string, value int64, usage string) { 682 f.Var(newInt64Value(value, p), name, usage) 683 } 684 685 // Int64Var defines an int64 flag with specified name, default value, and usage string. 686 // The argument p points to an int64 variable in which to store the value of the flag. 687 func Int64Var(p *int64, name string, value int64, usage string) { 688 CommandLine.Var(newInt64Value(value, p), name, usage) 689 } 690 691 // Int64 defines an int64 flag with specified name, default value, and usage string. 692 // The return value is the address of an int64 variable that stores the value of the flag. 693 func (f *FlagSet) Int64(name string, value int64, usage string) *int64 { 694 p := new(int64) 695 f.Int64Var(p, name, value, usage) 696 return p 697 } 698 699 // Int64 defines an int64 flag with specified name, default value, and usage string. 700 // The return value is the address of an int64 variable that stores the value of the flag. 701 func Int64(name string, value int64, usage string) *int64 { 702 return CommandLine.Int64(name, value, usage) 703 } 704 705 // UintVar defines a uint flag with specified name, default value, and usage string. 706 // The argument p points to a uint variable in which to store the value of the flag. 707 func (f *FlagSet) UintVar(p *uint, name string, value uint, usage string) { 708 f.Var(newUintValue(value, p), name, usage) 709 } 710 711 // UintVar defines a uint flag with specified name, default value, and usage string. 712 // The argument p points to a uint variable in which to store the value of the flag. 713 func UintVar(p *uint, name string, value uint, usage string) { 714 CommandLine.Var(newUintValue(value, p), name, usage) 715 } 716 717 // Uint defines a uint flag with specified name, default value, and usage string. 718 // The return value is the address of a uint variable that stores the value of the flag. 719 func (f *FlagSet) Uint(name string, value uint, usage string) *uint { 720 p := new(uint) 721 f.UintVar(p, name, value, usage) 722 return p 723 } 724 725 // Uint defines a uint flag with specified name, default value, and usage string. 726 // The return value is the address of a uint variable that stores the value of the flag. 727 func Uint(name string, value uint, usage string) *uint { 728 return CommandLine.Uint(name, value, usage) 729 } 730 731 // Uint64Var defines a uint64 flag with specified name, default value, and usage string. 732 // The argument p points to a uint64 variable in which to store the value of the flag. 733 func (f *FlagSet) Uint64Var(p *uint64, name string, value uint64, usage string) { 734 f.Var(newUint64Value(value, p), name, usage) 735 } 736 737 // Uint64Var defines a uint64 flag with specified name, default value, and usage string. 738 // The argument p points to a uint64 variable in which to store the value of the flag. 739 func Uint64Var(p *uint64, name string, value uint64, usage string) { 740 CommandLine.Var(newUint64Value(value, p), name, usage) 741 } 742 743 // Uint64 defines a uint64 flag with specified name, default value, and usage string. 744 // The return value is the address of a uint64 variable that stores the value of the flag. 745 func (f *FlagSet) Uint64(name string, value uint64, usage string) *uint64 { 746 p := new(uint64) 747 f.Uint64Var(p, name, value, usage) 748 return p 749 } 750 751 // Uint64 defines a uint64 flag with specified name, default value, and usage string. 752 // The return value is the address of a uint64 variable that stores the value of the flag. 753 func Uint64(name string, value uint64, usage string) *uint64 { 754 return CommandLine.Uint64(name, value, usage) 755 } 756 757 // StringVar defines a string flag with specified name, default value, and usage string. 758 // The argument p points to a string variable in which to store the value of the flag. 759 func (f *FlagSet) StringVar(p *string, name string, value string, usage string) { 760 f.Var(newStringValue(value, p), name, usage) 761 } 762 763 // StringVar defines a string flag with specified name, default value, and usage string. 764 // The argument p points to a string variable in which to store the value of the flag. 765 func StringVar(p *string, name string, value string, usage string) { 766 CommandLine.Var(newStringValue(value, p), name, usage) 767 } 768 769 // String defines a string flag with specified name, default value, and usage string. 770 // The return value is the address of a string variable that stores the value of the flag. 771 func (f *FlagSet) String(name string, value string, usage string) *string { 772 p := new(string) 773 f.StringVar(p, name, value, usage) 774 return p 775 } 776 777 // String defines a string flag with specified name, default value, and usage string. 778 // The return value is the address of a string variable that stores the value of the flag. 779 func String(name string, value string, usage string) *string { 780 return CommandLine.String(name, value, usage) 781 } 782 783 // Float64Var defines a float64 flag with specified name, default value, and usage string. 784 // The argument p points to a float64 variable in which to store the value of the flag. 785 func (f *FlagSet) Float64Var(p *float64, name string, value float64, usage string) { 786 f.Var(newFloat64Value(value, p), name, usage) 787 } 788 789 // Float64Var defines a float64 flag with specified name, default value, and usage string. 790 // The argument p points to a float64 variable in which to store the value of the flag. 791 func Float64Var(p *float64, name string, value float64, usage string) { 792 CommandLine.Var(newFloat64Value(value, p), name, usage) 793 } 794 795 // Float64 defines a float64 flag with specified name, default value, and usage string. 796 // The return value is the address of a float64 variable that stores the value of the flag. 797 func (f *FlagSet) Float64(name string, value float64, usage string) *float64 { 798 p := new(float64) 799 f.Float64Var(p, name, value, usage) 800 return p 801 } 802 803 // Float64 defines a float64 flag with specified name, default value, and usage string. 804 // The return value is the address of a float64 variable that stores the value of the flag. 805 func Float64(name string, value float64, usage string) *float64 { 806 return CommandLine.Float64(name, value, usage) 807 } 808 809 // DurationVar defines a time.Duration flag with specified name, default value, and usage string. 810 // The argument p points to a time.Duration variable in which to store the value of the flag. 811 // The flag accepts a value acceptable to time.ParseDuration. 812 func (f *FlagSet) DurationVar(p *time.Duration, name string, value time.Duration, usage string) { 813 f.Var(newDurationValue(value, p), name, usage) 814 } 815 816 // DurationVar defines a time.Duration flag with specified name, default value, and usage string. 817 // The argument p points to a time.Duration variable in which to store the value of the flag. 818 // The flag accepts a value acceptable to time.ParseDuration. 819 func DurationVar(p *time.Duration, name string, value time.Duration, usage string) { 820 CommandLine.Var(newDurationValue(value, p), name, usage) 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 (f *FlagSet) Duration(name string, value time.Duration, usage string) *time.Duration { 827 p := new(time.Duration) 828 f.DurationVar(p, name, value, usage) 829 return p 830 } 831 832 // Duration defines a time.Duration flag with specified name, default value, and usage string. 833 // The return value is the address of a time.Duration variable that stores the value of the flag. 834 // The flag accepts a value acceptable to time.ParseDuration. 835 func Duration(name string, value time.Duration, usage string) *time.Duration { 836 return CommandLine.Duration(name, value, usage) 837 } 838 839 // Func defines a flag with the specified name and usage string. 840 // Each time the flag is seen, fn is called with the value of the flag. 841 // If fn returns a non-nil error, it will be treated as a flag value parsing error. 842 func (f *FlagSet) Func(name, usage string, fn func(string) error) { 843 f.Var(funcValue(fn), name, usage) 844 } 845 846 // Func defines a flag with the specified name and usage string. 847 // Each time the flag is seen, fn is called with the value of the flag. 848 // If fn returns a non-nil error, it will be treated as a flag value parsing error. 849 func Func(name, usage string, fn func(string) error) { 850 CommandLine.Func(name, usage, fn) 851 } 852 853 // Var defines a flag with the specified name and usage string. The type and 854 // value of the flag are represented by the first argument, of type Value, which 855 // typically holds a user-defined implementation of Value. For instance, the 856 // caller could create a flag that turns a comma-separated string into a slice 857 // of strings by giving the slice the methods of Value; in particular, Set would 858 // decompose the comma-separated string into the slice. 859 func (f *FlagSet) Var(value Value, name string, usage string) { 860 // Remember the default value as a string; it won't change. 861 flag := &Flag{name, usage, value, value.String()} 862 _, alreadythere := f.formal[name] 863 if alreadythere { 864 var msg string 865 if f.name == "" { 866 msg = fmt.Sprintf("flag redefined: %s", name) 867 } else { 868 msg = fmt.Sprintf("%s flag redefined: %s", f.name, name) 869 } 870 fmt.Fprintln(f.Output(), msg) 871 panic(msg) // Happens only if flags are declared with identical names 872 } 873 if f.formal == nil { 874 f.formal = make(map[string]*Flag) 875 } 876 f.formal[name] = flag 877 } 878 879 // Var defines a flag with the specified name and usage string. The type and 880 // value of the flag are represented by the first argument, of type Value, which 881 // typically holds a user-defined implementation of Value. For instance, the 882 // caller could create a flag that turns a comma-separated string into a slice 883 // of strings by giving the slice the methods of Value; in particular, Set would 884 // decompose the comma-separated string into the slice. 885 func Var(value Value, name string, usage string) { 886 CommandLine.Var(value, name, usage) 887 } 888 889 // failf prints to standard error a formatted error and usage message and 890 // returns the error. 891 func (f *FlagSet) failf(format string, a ...interface{}) error { 892 err := fmt.Errorf(format, a...) 893 fmt.Fprintln(f.Output(), err) 894 f.usage() 895 return err 896 } 897 898 // usage calls the Usage method for the flag set if one is specified, 899 // or the appropriate default usage function otherwise. 900 func (f *FlagSet) usage() { 901 if f.Usage == nil { 902 f.defaultUsage() 903 } else { 904 f.Usage() 905 } 906 } 907 908 // parseOne parses one flag. It reports whether a flag was seen. 909 func (f *FlagSet) parseOne() (bool, error) { 910 if len(f.args) == 0 { 911 return false, nil 912 } 913 s := f.args[0] 914 if len(s) < 2 || s[0] != '-' { 915 return false, nil 916 } 917 numMinuses := 1 918 if s[1] == '-' { 919 numMinuses++ 920 if len(s) == 2 { // "--" terminates the flags 921 f.args = f.args[1:] 922 return false, nil 923 } 924 } 925 name := s[numMinuses:] 926 if len(name) == 0 || name[0] == '-' || name[0] == '=' { 927 return false, f.failf("bad flag syntax: %s", s) 928 } 929 930 // it's a flag. does it have an argument? 931 f.args = f.args[1:] 932 hasValue := false 933 value := "" 934 for i := 1; i < len(name); i++ { // equals cannot be first 935 if name[i] == '=' { 936 value = name[i+1:] 937 hasValue = true 938 name = name[0:i] 939 break 940 } 941 } 942 m := f.formal 943 flag, alreadythere := m[name] // BUG 944 if !alreadythere { 945 if name == "help" || name == "h" { // special case for nice help message. 946 f.usage() 947 return false, ErrHelp 948 } 949 return false, f.failf("flag provided but not defined: -%s", name) 950 } 951 952 if fv, ok := flag.Value.(boolFlag); ok && fv.IsBoolFlag() { // special case: doesn't need an arg 953 if hasValue { 954 if err := fv.Set(value); err != nil { 955 return false, f.failf("invalid boolean value %q for -%s: %v", value, name, err) 956 } 957 } else { 958 if err := fv.Set("true"); err != nil { 959 return false, f.failf("invalid boolean flag %s: %v", name, err) 960 } 961 } 962 } else { 963 // It must have a value, which might be the next argument. 964 if !hasValue && len(f.args) > 0 { 965 // value is the next arg 966 hasValue = true 967 value, f.args = f.args[0], f.args[1:] 968 } 969 if !hasValue { 970 return false, f.failf("flag needs an argument: -%s", name) 971 } 972 if err := flag.Value.Set(value); err != nil { 973 return false, f.failf("invalid value %q for flag -%s: %v", value, name, err) 974 } 975 } 976 if f.actual == nil { 977 f.actual = make(map[string]*Flag) 978 } 979 f.actual[name] = flag 980 return true, nil 981 } 982 983 // Parse parses flag definitions from the argument list, which should not 984 // include the command name. Must be called after all flags in the FlagSet 985 // are defined and before flags are accessed by the program. 986 // The return value will be ErrHelp if -help or -h were set but not defined. 987 func (f *FlagSet) Parse(arguments []string) error { 988 f.parsed = true 989 f.args = arguments 990 for { 991 seen, err := f.parseOne() 992 if seen { 993 continue 994 } 995 if err == nil { 996 break 997 } 998 switch f.errorHandling { 999 case ContinueOnError: 1000 return err 1001 case ExitOnError: 1002 if err == ErrHelp { 1003 os.Exit(0) 1004 } 1005 os.Exit(2) 1006 case PanicOnError: 1007 panic(err) 1008 } 1009 } 1010 return nil 1011 } 1012 1013 // Parsed reports whether f.Parse has been called. 1014 func (f *FlagSet) Parsed() bool { 1015 return f.parsed 1016 } 1017 1018 // Parse parses the command-line flags from os.Args[1:]. Must be called 1019 // after all flags are defined and before flags are accessed by the program. 1020 func Parse() { 1021 // Ignore errors; CommandLine is set for ExitOnError. 1022 CommandLine.Parse(os.Args[1:]) 1023 } 1024 1025 // Parsed reports whether the command-line flags have been parsed. 1026 func Parsed() bool { 1027 return CommandLine.Parsed() 1028 } 1029 1030 // CommandLine is the default set of command-line flags, parsed from os.Args. 1031 // The top-level functions such as BoolVar, Arg, and so on are wrappers for the 1032 // methods of CommandLine. 1033 var CommandLine = NewFlagSet(os.Args[0], ExitOnError) 1034 1035 func init() { 1036 // Override generic FlagSet default Usage with call to global Usage. 1037 // Note: This is not CommandLine.Usage = Usage, 1038 // because we want any eventual call to use any updated value of Usage, 1039 // not the value it has when this line is run. 1040 CommandLine.Usage = commandLineUsage 1041 } 1042 1043 func commandLineUsage() { 1044 Usage() 1045 } 1046 1047 // NewFlagSet returns a new, empty flag set with the specified name and 1048 // error handling property. If the name is not empty, it will be printed 1049 // in the default usage message and in error messages. 1050 func NewFlagSet(name string, errorHandling ErrorHandling) *FlagSet { 1051 f := &FlagSet{ 1052 name: name, 1053 errorHandling: errorHandling, 1054 } 1055 f.Usage = f.defaultUsage 1056 return f 1057 } 1058 1059 // Init sets the name and error handling property for a flag set. 1060 // By default, the zero FlagSet uses an empty name and the 1061 // ContinueOnError error handling policy. 1062 func (f *FlagSet) Init(name string, errorHandling ErrorHandling) { 1063 f.name = name 1064 f.errorHandling = errorHandling 1065 } 1066