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 var b strings.Builder 512 fmt.Fprintf(&b, " -%s", flag.Name) // Two spaces before -; see next two comments. 513 name, usage := UnquoteUsage(flag) 514 if len(name) > 0 { 515 b.WriteString(" ") 516 b.WriteString(name) 517 } 518 // Boolean flags of one ASCII letter are so common we 519 // treat them specially, putting their usage on the same line. 520 if b.Len() <= 4 { // space, space, '-', 'x'. 521 b.WriteString("\t") 522 } else { 523 // Four spaces before the tab triggers good alignment 524 // for both 4- and 8-space tab stops. 525 b.WriteString("\n \t") 526 } 527 b.WriteString(strings.ReplaceAll(usage, "\n", "\n \t")) 528 529 if !isZeroValue(flag, flag.DefValue) { 530 if _, ok := flag.Value.(*stringValue); ok { 531 // put quotes on the value 532 fmt.Fprintf(&b, " (default %q)", flag.DefValue) 533 } else { 534 fmt.Fprintf(&b, " (default %v)", flag.DefValue) 535 } 536 } 537 fmt.Fprint(f.Output(), b.String(), "\n") 538 }) 539 } 540 541 // PrintDefaults prints, to standard error unless configured otherwise, 542 // a usage message showing the default settings of all defined 543 // command-line flags. 544 // For an integer valued flag x, the default output has the form 545 // -x int 546 // usage-message-for-x (default 7) 547 // The usage message will appear on a separate line for anything but 548 // a bool flag with a one-byte name. For bool flags, the type is 549 // omitted and if the flag name is one byte the usage message appears 550 // on the same line. The parenthetical default is omitted if the 551 // default is the zero value for the type. The listed type, here int, 552 // can be changed by placing a back-quoted name in the flag's usage 553 // string; the first such item in the message is taken to be a parameter 554 // name to show in the message and the back quotes are stripped from 555 // the message when displayed. For instance, given 556 // flag.String("I", "", "search `directory` for include files") 557 // the output will be 558 // -I directory 559 // search directory for include files. 560 // 561 // To change the destination for flag messages, call CommandLine.SetOutput. 562 func PrintDefaults() { 563 CommandLine.PrintDefaults() 564 } 565 566 // defaultUsage is the default function to print a usage message. 567 func (f *FlagSet) defaultUsage() { 568 if f.name == "" { 569 fmt.Fprintf(f.Output(), "Usage:\n") 570 } else { 571 fmt.Fprintf(f.Output(), "Usage of %s:\n", f.name) 572 } 573 f.PrintDefaults() 574 } 575 576 // NOTE: Usage is not just defaultUsage(CommandLine) 577 // because it serves (via godoc flag Usage) as the example 578 // for how to write your own usage function. 579 580 // Usage prints a usage message documenting all defined command-line flags 581 // to CommandLine's output, which by default is os.Stderr. 582 // It is called when an error occurs while parsing flags. 583 // The function is a variable that may be changed to point to a custom function. 584 // By default it prints a simple header and calls PrintDefaults; for details about the 585 // format of the output and how to control it, see the documentation for PrintDefaults. 586 // Custom usage functions may choose to exit the program; by default exiting 587 // happens anyway as the command line's error handling strategy is set to 588 // ExitOnError. 589 var Usage = func() { 590 fmt.Fprintf(CommandLine.Output(), "Usage of %s:\n", os.Args[0]) 591 PrintDefaults() 592 } 593 594 // NFlag returns the number of flags that have been set. 595 func (f *FlagSet) NFlag() int { return len(f.actual) } 596 597 // NFlag returns the number of command-line flags that have been set. 598 func NFlag() int { return len(CommandLine.actual) } 599 600 // Arg returns the i'th argument. Arg(0) is the first remaining argument 601 // after flags have been processed. Arg returns an empty string if the 602 // requested element does not exist. 603 func (f *FlagSet) Arg(i int) string { 604 if i < 0 || i >= len(f.args) { 605 return "" 606 } 607 return f.args[i] 608 } 609 610 // Arg returns the i'th command-line argument. Arg(0) is the first remaining argument 611 // after flags have been processed. Arg returns an empty string if the 612 // requested element does not exist. 613 func Arg(i int) string { 614 return CommandLine.Arg(i) 615 } 616 617 // NArg is the number of arguments remaining after flags have been processed. 618 func (f *FlagSet) NArg() int { return len(f.args) } 619 620 // NArg is the number of arguments remaining after flags have been processed. 621 func NArg() int { return len(CommandLine.args) } 622 623 // Args returns the non-flag arguments. 624 func (f *FlagSet) Args() []string { return f.args } 625 626 // Args returns the non-flag command-line arguments. 627 func Args() []string { return CommandLine.args } 628 629 // BoolVar defines a bool flag with specified name, default value, and usage string. 630 // The argument p points to a bool variable in which to store the value of the flag. 631 func (f *FlagSet) BoolVar(p *bool, name string, value bool, usage string) { 632 f.Var(newBoolValue(value, p), name, usage) 633 } 634 635 // BoolVar defines a bool flag with specified name, default value, and usage string. 636 // The argument p points to a bool variable in which to store the value of the flag. 637 func BoolVar(p *bool, name string, value bool, usage string) { 638 CommandLine.Var(newBoolValue(value, p), name, usage) 639 } 640 641 // Bool defines a bool flag with specified name, default value, and usage string. 642 // The return value is the address of a bool variable that stores the value of the flag. 643 func (f *FlagSet) Bool(name string, value bool, usage string) *bool { 644 p := new(bool) 645 f.BoolVar(p, name, value, usage) 646 return p 647 } 648 649 // Bool defines a bool flag with specified name, default value, and usage string. 650 // The return value is the address of a bool variable that stores the value of the flag. 651 func Bool(name string, value bool, usage string) *bool { 652 return CommandLine.Bool(name, value, usage) 653 } 654 655 // IntVar defines an int flag with specified name, default value, and usage string. 656 // The argument p points to an int variable in which to store the value of the flag. 657 func (f *FlagSet) IntVar(p *int, name string, value int, usage string) { 658 f.Var(newIntValue(value, p), name, usage) 659 } 660 661 // IntVar defines an int flag with specified name, default value, and usage string. 662 // The argument p points to an int variable in which to store the value of the flag. 663 func IntVar(p *int, name string, value int, usage string) { 664 CommandLine.Var(newIntValue(value, p), name, usage) 665 } 666 667 // Int defines an int flag with specified name, default value, and usage string. 668 // The return value is the address of an int variable that stores the value of the flag. 669 func (f *FlagSet) Int(name string, value int, usage string) *int { 670 p := new(int) 671 f.IntVar(p, name, value, usage) 672 return p 673 } 674 675 // Int defines an int flag with specified name, default value, and usage string. 676 // The return value is the address of an int variable that stores the value of the flag. 677 func Int(name string, value int, usage string) *int { 678 return CommandLine.Int(name, value, usage) 679 } 680 681 // Int64Var defines an int64 flag with specified name, default value, and usage string. 682 // The argument p points to an int64 variable in which to store the value of the flag. 683 func (f *FlagSet) Int64Var(p *int64, name string, value int64, usage string) { 684 f.Var(newInt64Value(value, p), name, usage) 685 } 686 687 // Int64Var defines an int64 flag with specified name, default value, and usage string. 688 // The argument p points to an int64 variable in which to store the value of the flag. 689 func Int64Var(p *int64, name string, value int64, usage string) { 690 CommandLine.Var(newInt64Value(value, p), name, usage) 691 } 692 693 // Int64 defines an int64 flag with specified name, default value, and usage string. 694 // The return value is the address of an int64 variable that stores the value of the flag. 695 func (f *FlagSet) Int64(name string, value int64, usage string) *int64 { 696 p := new(int64) 697 f.Int64Var(p, name, value, usage) 698 return p 699 } 700 701 // Int64 defines an int64 flag with specified name, default value, and usage string. 702 // The return value is the address of an int64 variable that stores the value of the flag. 703 func Int64(name string, value int64, usage string) *int64 { 704 return CommandLine.Int64(name, value, usage) 705 } 706 707 // UintVar defines a uint flag with specified name, default value, and usage string. 708 // The argument p points to a uint variable in which to store the value of the flag. 709 func (f *FlagSet) UintVar(p *uint, name string, value uint, usage string) { 710 f.Var(newUintValue(value, p), name, usage) 711 } 712 713 // UintVar defines a uint flag with specified name, default value, and usage string. 714 // The argument p points to a uint variable in which to store the value of the flag. 715 func UintVar(p *uint, name string, value uint, usage string) { 716 CommandLine.Var(newUintValue(value, p), name, usage) 717 } 718 719 // Uint defines a uint flag with specified name, default value, and usage string. 720 // The return value is the address of a uint variable that stores the value of the flag. 721 func (f *FlagSet) Uint(name string, value uint, usage string) *uint { 722 p := new(uint) 723 f.UintVar(p, name, value, usage) 724 return p 725 } 726 727 // Uint defines a uint flag with specified name, default value, and usage string. 728 // The return value is the address of a uint variable that stores the value of the flag. 729 func Uint(name string, value uint, usage string) *uint { 730 return CommandLine.Uint(name, value, usage) 731 } 732 733 // Uint64Var defines a uint64 flag with specified name, default value, and usage string. 734 // The argument p points to a uint64 variable in which to store the value of the flag. 735 func (f *FlagSet) Uint64Var(p *uint64, name string, value uint64, usage string) { 736 f.Var(newUint64Value(value, p), name, usage) 737 } 738 739 // Uint64Var defines a uint64 flag with specified name, default value, and usage string. 740 // The argument p points to a uint64 variable in which to store the value of the flag. 741 func Uint64Var(p *uint64, name string, value uint64, usage string) { 742 CommandLine.Var(newUint64Value(value, p), name, usage) 743 } 744 745 // Uint64 defines a uint64 flag with specified name, default value, and usage string. 746 // The return value is the address of a uint64 variable that stores the value of the flag. 747 func (f *FlagSet) Uint64(name string, value uint64, usage string) *uint64 { 748 p := new(uint64) 749 f.Uint64Var(p, name, value, usage) 750 return p 751 } 752 753 // Uint64 defines a uint64 flag with specified name, default value, and usage string. 754 // The return value is the address of a uint64 variable that stores the value of the flag. 755 func Uint64(name string, value uint64, usage string) *uint64 { 756 return CommandLine.Uint64(name, value, usage) 757 } 758 759 // StringVar defines a string flag with specified name, default value, and usage string. 760 // The argument p points to a string variable in which to store the value of the flag. 761 func (f *FlagSet) StringVar(p *string, name string, value string, usage string) { 762 f.Var(newStringValue(value, p), name, usage) 763 } 764 765 // StringVar defines a string flag with specified name, default value, and usage string. 766 // The argument p points to a string variable in which to store the value of the flag. 767 func StringVar(p *string, name string, value string, usage string) { 768 CommandLine.Var(newStringValue(value, p), name, usage) 769 } 770 771 // String defines a string flag with specified name, default value, and usage string. 772 // The return value is the address of a string variable that stores the value of the flag. 773 func (f *FlagSet) String(name string, value string, usage string) *string { 774 p := new(string) 775 f.StringVar(p, name, value, usage) 776 return p 777 } 778 779 // String defines a string flag with specified name, default value, and usage string. 780 // The return value is the address of a string variable that stores the value of the flag. 781 func String(name string, value string, usage string) *string { 782 return CommandLine.String(name, value, usage) 783 } 784 785 // Float64Var defines a float64 flag with specified name, default value, and usage string. 786 // The argument p points to a float64 variable in which to store the value of the flag. 787 func (f *FlagSet) Float64Var(p *float64, name string, value float64, usage string) { 788 f.Var(newFloat64Value(value, p), name, usage) 789 } 790 791 // Float64Var defines a float64 flag with specified name, default value, and usage string. 792 // The argument p points to a float64 variable in which to store the value of the flag. 793 func Float64Var(p *float64, name string, value float64, usage string) { 794 CommandLine.Var(newFloat64Value(value, p), name, usage) 795 } 796 797 // Float64 defines a float64 flag with specified name, default value, and usage string. 798 // The return value is the address of a float64 variable that stores the value of the flag. 799 func (f *FlagSet) Float64(name string, value float64, usage string) *float64 { 800 p := new(float64) 801 f.Float64Var(p, name, value, usage) 802 return p 803 } 804 805 // Float64 defines a float64 flag with specified name, default value, and usage string. 806 // The return value is the address of a float64 variable that stores the value of the flag. 807 func Float64(name string, value float64, usage string) *float64 { 808 return CommandLine.Float64(name, value, usage) 809 } 810 811 // DurationVar defines a time.Duration flag with specified name, default value, and usage string. 812 // The argument p points to a time.Duration variable in which to store the value of the flag. 813 // The flag accepts a value acceptable to time.ParseDuration. 814 func (f *FlagSet) DurationVar(p *time.Duration, name string, value time.Duration, usage string) { 815 f.Var(newDurationValue(value, p), name, usage) 816 } 817 818 // DurationVar defines a time.Duration flag with specified name, default value, and usage string. 819 // The argument p points to a time.Duration variable in which to store the value of the flag. 820 // The flag accepts a value acceptable to time.ParseDuration. 821 func DurationVar(p *time.Duration, name string, value time.Duration, usage string) { 822 CommandLine.Var(newDurationValue(value, p), name, usage) 823 } 824 825 // Duration defines a time.Duration flag with specified name, default value, and usage string. 826 // The return value is the address of a time.Duration variable that stores the value of the flag. 827 // The flag accepts a value acceptable to time.ParseDuration. 828 func (f *FlagSet) Duration(name string, value time.Duration, usage string) *time.Duration { 829 p := new(time.Duration) 830 f.DurationVar(p, name, value, usage) 831 return p 832 } 833 834 // Duration defines a time.Duration flag with specified name, default value, and usage string. 835 // The return value is the address of a time.Duration variable that stores the value of the flag. 836 // The flag accepts a value acceptable to time.ParseDuration. 837 func Duration(name string, value time.Duration, usage string) *time.Duration { 838 return CommandLine.Duration(name, value, usage) 839 } 840 841 // Func defines a flag with the specified name and usage string. 842 // Each time the flag is seen, fn is called with the value of the flag. 843 // If fn returns a non-nil error, it will be treated as a flag value parsing error. 844 func (f *FlagSet) Func(name, usage string, fn func(string) error) { 845 f.Var(funcValue(fn), name, usage) 846 } 847 848 // Func defines a flag with the specified name and usage string. 849 // Each time the flag is seen, fn is called with the value of the flag. 850 // If fn returns a non-nil error, it will be treated as a flag value parsing error. 851 func Func(name, usage string, fn func(string) error) { 852 CommandLine.Func(name, usage, fn) 853 } 854 855 // Var defines a flag with the specified name and usage string. The type and 856 // value of the flag are represented by the first argument, of type Value, which 857 // typically holds a user-defined implementation of Value. For instance, the 858 // caller could create a flag that turns a comma-separated string into a slice 859 // of strings by giving the slice the methods of Value; in particular, Set would 860 // decompose the comma-separated string into the slice. 861 func (f *FlagSet) Var(value Value, name string, usage string) { 862 // Flag must not begin "-" or contain "=". 863 if strings.HasPrefix(name, "-") { 864 panic(f.sprintf("flag %q begins with -", name)) 865 } else if strings.Contains(name, "=") { 866 panic(f.sprintf("flag %q contains =", name)) 867 } 868 869 // Remember the default value as a string; it won't change. 870 flag := &Flag{name, usage, value, value.String()} 871 _, alreadythere := f.formal[name] 872 if alreadythere { 873 var msg string 874 if f.name == "" { 875 msg = f.sprintf("flag redefined: %s", name) 876 } else { 877 msg = f.sprintf("%s flag redefined: %s", f.name, name) 878 } 879 panic(msg) // Happens only if flags are declared with identical names 880 } 881 if f.formal == nil { 882 f.formal = make(map[string]*Flag) 883 } 884 f.formal[name] = flag 885 } 886 887 // Var defines a flag with the specified name and usage string. The type and 888 // value of the flag are represented by the first argument, of type Value, which 889 // typically holds a user-defined implementation of Value. For instance, the 890 // caller could create a flag that turns a comma-separated string into a slice 891 // of strings by giving the slice the methods of Value; in particular, Set would 892 // decompose the comma-separated string into the slice. 893 func Var(value Value, name string, usage string) { 894 CommandLine.Var(value, name, usage) 895 } 896 897 // sprintf formats the message, prints it to output, and returns it. 898 func (f *FlagSet) sprintf(format string, a ...interface{}) string { 899 msg := fmt.Sprintf(format, a...) 900 fmt.Fprintln(f.Output(), msg) 901 return msg 902 } 903 904 // failf prints to standard error a formatted error and usage message and 905 // returns the error. 906 func (f *FlagSet) failf(format string, a ...interface{}) error { 907 msg := f.sprintf(format, a...) 908 f.usage() 909 return errors.New(msg) 910 } 911 912 // usage calls the Usage method for the flag set if one is specified, 913 // or the appropriate default usage function otherwise. 914 func (f *FlagSet) usage() { 915 if f.Usage == nil { 916 f.defaultUsage() 917 } else { 918 f.Usage() 919 } 920 } 921 922 // parseOne parses one flag. It reports whether a flag was seen. 923 func (f *FlagSet) parseOne() (bool, error) { 924 if len(f.args) == 0 { 925 return false, nil 926 } 927 s := f.args[0] 928 if len(s) < 2 || s[0] != '-' { 929 return false, nil 930 } 931 numMinuses := 1 932 if s[1] == '-' { 933 numMinuses++ 934 if len(s) == 2 { // "--" terminates the flags 935 f.args = f.args[1:] 936 return false, nil 937 } 938 } 939 name := s[numMinuses:] 940 if len(name) == 0 || name[0] == '-' || name[0] == '=' { 941 return false, f.failf("bad flag syntax: %s", s) 942 } 943 944 // it's a flag. does it have an argument? 945 f.args = f.args[1:] 946 hasValue := false 947 value := "" 948 for i := 1; i < len(name); i++ { // equals cannot be first 949 if name[i] == '=' { 950 value = name[i+1:] 951 hasValue = true 952 name = name[0:i] 953 break 954 } 955 } 956 m := f.formal 957 flag, alreadythere := m[name] // BUG 958 if !alreadythere { 959 if name == "help" || name == "h" { // special case for nice help message. 960 f.usage() 961 return false, ErrHelp 962 } 963 return false, f.failf("flag provided but not defined: -%s", name) 964 } 965 966 if fv, ok := flag.Value.(boolFlag); ok && fv.IsBoolFlag() { // special case: doesn't need an arg 967 if hasValue { 968 if err := fv.Set(value); err != nil { 969 return false, f.failf("invalid boolean value %q for -%s: %v", value, name, err) 970 } 971 } else { 972 if err := fv.Set("true"); err != nil { 973 return false, f.failf("invalid boolean flag %s: %v", name, err) 974 } 975 } 976 } else { 977 // It must have a value, which might be the next argument. 978 if !hasValue && len(f.args) > 0 { 979 // value is the next arg 980 hasValue = true 981 value, f.args = f.args[0], f.args[1:] 982 } 983 if !hasValue { 984 return false, f.failf("flag needs an argument: -%s", name) 985 } 986 if err := flag.Value.Set(value); err != nil { 987 return false, f.failf("invalid value %q for flag -%s: %v", value, name, err) 988 } 989 } 990 if f.actual == nil { 991 f.actual = make(map[string]*Flag) 992 } 993 f.actual[name] = flag 994 return true, nil 995 } 996 997 // Parse parses flag definitions from the argument list, which should not 998 // include the command name. Must be called after all flags in the FlagSet 999 // are defined and before flags are accessed by the program. 1000 // The return value will be ErrHelp if -help or -h were set but not defined. 1001 func (f *FlagSet) Parse(arguments []string) error { 1002 f.parsed = true 1003 f.args = arguments 1004 for { 1005 seen, err := f.parseOne() 1006 if seen { 1007 continue 1008 } 1009 if err == nil { 1010 break 1011 } 1012 switch f.errorHandling { 1013 case ContinueOnError: 1014 return err 1015 case ExitOnError: 1016 if err == ErrHelp { 1017 os.Exit(0) 1018 } 1019 os.Exit(2) 1020 case PanicOnError: 1021 panic(err) 1022 } 1023 } 1024 return nil 1025 } 1026 1027 // Parsed reports whether f.Parse has been called. 1028 func (f *FlagSet) Parsed() bool { 1029 return f.parsed 1030 } 1031 1032 // Parse parses the command-line flags from os.Args[1:]. Must be called 1033 // after all flags are defined and before flags are accessed by the program. 1034 func Parse() { 1035 // Ignore errors; CommandLine is set for ExitOnError. 1036 CommandLine.Parse(os.Args[1:]) 1037 } 1038 1039 // Parsed reports whether the command-line flags have been parsed. 1040 func Parsed() bool { 1041 return CommandLine.Parsed() 1042 } 1043 1044 // CommandLine is the default set of command-line flags, parsed from os.Args. 1045 // The top-level functions such as BoolVar, Arg, and so on are wrappers for the 1046 // methods of CommandLine. 1047 var CommandLine = NewFlagSet(os.Args[0], ExitOnError) 1048 1049 func init() { 1050 // Override generic FlagSet default Usage with call to global Usage. 1051 // Note: This is not CommandLine.Usage = Usage, 1052 // because we want any eventual call to use any updated value of Usage, 1053 // not the value it has when this line is run. 1054 CommandLine.Usage = commandLineUsage 1055 } 1056 1057 func commandLineUsage() { 1058 Usage() 1059 } 1060 1061 // NewFlagSet returns a new, empty flag set with the specified name and 1062 // error handling property. If the name is not empty, it will be printed 1063 // in the default usage message and in error messages. 1064 func NewFlagSet(name string, errorHandling ErrorHandling) *FlagSet { 1065 f := &FlagSet{ 1066 name: name, 1067 errorHandling: errorHandling, 1068 } 1069 f.Usage = f.defaultUsage 1070 return f 1071 } 1072 1073 // Init sets the name and error handling property for a flag set. 1074 // By default, the zero FlagSet uses an empty name and the 1075 // ContinueOnError error handling policy. 1076 func (f *FlagSet) Init(name string, errorHandling ErrorHandling) { 1077 f.name = name 1078 f.errorHandling = errorHandling 1079 } 1080