After parsing, the arguments after the flag are available as the
slice flag.Args() or individually as flag.Arg(i).
- The arguments are indexed from 0 up to flag.NArg().
+ The arguments are indexed from 0 through flag.NArg()-1.
Command line flag syntax:
-flag
func (b *boolValue) String() string { return fmt.Sprintf("%v", *b) }
+func (b *boolValue) IsBoolFlag() bool { return true }
+
+// optional interface to indicate boolean flags that can be
+// supplied without "=value" text
+type boolFlag interface {
+ Value
+ IsBoolFlag() bool
+}
+
// -- int Value
type intValue int
// Value is the interface to the dynamic value stored in a flag.
// (The default value is represented as a string.)
+//
+// If a Value has an IsBoolFlag() bool method returning true,
+// the command-line parser makes -name equivalent to -name=true
+// rather than using the next command-line argument.
type Value interface {
String() string
Set(string) error
}
return false, f.failf("flag provided but not defined: -%s", name)
}
- if fv, ok := flag.Value.(*boolValue); ok { // special case: doesn't need an arg
+ if fv, ok := flag.Value.(boolFlag); ok && fv.IsBoolFlag() { // special case: doesn't need an arg
if has_value {
if err := fv.Set(value); err != nil {
- f.failf("invalid boolean value %q for -%s: %v", value, name, err)
+ return false, f.failf("invalid boolean value %q for -%s: %v", value, name, err)
}
} else {
fv.Set("true")