Package regexp
import "regexp"
Package regexp implements a simple regular expression library.
The syntax of the regular expressions accepted is:
regexp:
concatenation { '|' concatenation }
concatenation:
{ closure }
closure:
term [ '*' | '+' | '?' ]
term:
'^'
'$'
'.'
character
'[' [ '^' ] { character-range } ']'
'(' regexp ')'
character-range:
character [ '-' character ]
All characters are UTF-8-encoded code points. Backslashes escape special characters, including inside character classes.
There are 16 methods of Regexp that match a regular expression and identify the matched text. Their names are matched by this regular expression:
Find(All)?(String)?(Submatch)?(Index)?
If 'All' is present, the routine matches successive non-overlapping matches of the entire expression. Empty matches abutting a preceding match are ignored. The return value is a slice containing the successive return values of the corresponding non-'All' routine. These routines take an extra integer argument, n; if n >= 0, the function returns at most n matches/submatches.
If 'String' is present, the argument is a string; otherwise it is a slice of bytes; return values are adjusted as appropriate.
If 'Submatch' is present, the return value is a slice identifying the successive submatches of the expression. Submatches are matches of parenthesized subexpressions within the regular expression, numbered from left to right in order of opening parenthesis. Submatch 0 is the match of the entire expression, submatch 1 the match of the first parenthesized subexpression, and so on.
If 'Index' is present, matches and submatches are identified by byte index pairs within the input string: result[2*n:2*n+1] identifies the indexes of the nth submatch. The pair for n==0 identifies the match of the entire expression. If 'Index' is not present, the match is identified by the text of the match/submatch. If an index is negative, it means that subexpression did not match any string in the input.
(There are a few other methods that do not match this pattern.)
Package files
regexp.goVariables
Error codes returned by failures to parse an expression.
var (
ErrInternal = Error("internal error")
ErrUnmatchedLpar = Error("unmatched '('")
ErrUnmatchedRpar = Error("unmatched ')'")
ErrUnmatchedLbkt = Error("unmatched '['")
ErrUnmatchedRbkt = Error("unmatched ']'")
ErrBadRange = Error("bad range in character class")
ErrExtraneousBackslash = Error("extraneous backslash")
ErrBadClosure = Error("repeated closure (**, ++, etc.)")
ErrBareClosure = Error("closure applies to nothing")
ErrBadBackslash = Error("illegal backslash escape")
)
func Match
func Match(pattern string, b []byte) (matched bool, error os.Error)
Match checks whether a textual regular expression matches a byte slice. More complicated queries need to use Compile and the full Regexp interface.
func MatchString
func MatchString(pattern string, s string) (matched bool, error os.Error)
MatchString checks whether a textual regular expression matches a string. More complicated queries need to use Compile and the full Regexp interface.
func QuoteMeta
func QuoteMeta(s string) string
QuoteMeta returns a string that quotes all regular expression metacharacters inside the argument text; the returned string is a regular expression matching the literal text. For example, QuoteMeta(`[foo]`) returns `\[foo\]`.
type Error
Error is the local type for a parsing error.
type Error string
func (Error) String
func (e Error) String() string
type Regexp
Regexp is the representation of a compiled regular expression. The public interface is entirely through methods.
type Regexp struct {
// contains unexported fields
}
func Compile
func Compile(str string) (regexp *Regexp, error os.Error)
Compile parses a regular expression and returns, if successful, a Regexp object that can be used to match against text.
func MustCompile
func MustCompile(str string) *Regexp
MustCompile is like Compile but panics if the expression cannot be parsed. It simplifies safe initialization of global variables holding compiled regular expressions.
func (*Regexp) AllMatchesIter
func (re *Regexp) AllMatchesIter(b []byte, n int) <-chan []byte
AllMatchesIter slices the byte slice b into substrings that are successive matches of the Regexp within b. If n > 0, the function returns at most n matches. Text that does not match the expression will be skipped. Empty matches abutting a preceding match are ignored. The function returns a channel that iterates over the matching substrings.
func (*Regexp) AllMatchesStringIter
func (re *Regexp) AllMatchesStringIter(s string, n int) <-chan string
AllMatchesStringIter slices the string s into substrings that are successive matches of the Regexp within s. If n > 0, the function returns at most n matches. Text that does not match the expression will be skipped. Empty matches abutting a preceding match are ignored. The function returns a channel that iterates over the matching substrings.
func (*Regexp) Find
func (re *Regexp) Find(b []byte) []byte
Find returns a slice holding the text of the leftmost match in b of the regular expression. A return value of nil indicates no match.
func (*Regexp) FindAll
func (re *Regexp) FindAll(b []byte, n int) [][]byte
FindAll is the 'All' version of Find; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindAllIndex
func (re *Regexp) FindAllIndex(b []byte, n int) [][]int
FindAllIndex is the 'All' version of FindIndex; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindAllString
func (re *Regexp) FindAllString(s string, n int) []string
FindAllString is the 'All' version of FindString; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindAllStringIndex
func (re *Regexp) FindAllStringIndex(s string, n int) [][]int
FindAllStringIndex is the 'All' version of FindStringIndex; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindAllStringSubmatch
func (re *Regexp) FindAllStringSubmatch(s string, n int) [][]string
FindAllStringSubmatch is the 'All' version of FindStringSubmatch; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindAllStringSubmatchIndex
func (re *Regexp) FindAllStringSubmatchIndex(s string, n int) [][]int
FindAllStringSubmatchIndex is the 'All' version of FindStringSubmatchIndex; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindAllSubmatch
func (re *Regexp) FindAllSubmatch(b []byte, n int) [][][]byte
FindAllSubmatch is the 'All' version of FindSubmatch; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindAllSubmatchIndex
func (re *Regexp) FindAllSubmatchIndex(b []byte, n int) [][]int
FindAllSubmatchIndex is the 'All' version of FindSubmatchIndex; it returns a slice of all successive matches of the expression, as defined by the 'All' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindIndex
func (re *Regexp) FindIndex(b []byte) (loc []int)
FindIndex returns a two-element slice of integers defining the location of the leftmost match in b of the regular expression. The match itself is at b[loc[0]:loc[1]]. A return value of nil indicates no match.
func (*Regexp) FindString
func (re *Regexp) FindString(s string) string
FindString returns a string holding the text of the leftmost match in s of the regular expression. If there is no match, the return value is an empty string, but it will also be empty if the regular expression successfully matches an empty string. Use FindStringIndex or FindStringSubmatch if it is necessary to distinguish these cases.
func (*Regexp) FindStringIndex
func (re *Regexp) FindStringIndex(s string) []int
FindStringIndex returns a two-element slice of integers defining the location of the leftmost match in s of the regular expression. The match itself is at s[loc[0]:loc[1]]. A return value of nil indicates no match.
func (*Regexp) FindStringSubmatch
func (re *Regexp) FindStringSubmatch(s string) []string
FindStringSubmatch returns a slice of strings holding the text of the leftmost match of the regular expression in s and the matches, if any, of its subexpressions, as defined by the 'Submatch' description in the package comment. A return value of nil indicates no match.
func (*Regexp) FindStringSubmatchIndex
func (re *Regexp) FindStringSubmatchIndex(s string) []int
FindStringSubmatchIndex returns a slice holding the index pairs identifying the leftmost match of the regular expression in s and the matches, if any, of its subexpressions, as defined by the 'Submatch' and 'Index' descriptions in the package comment. A return value of nil indicates no match.
func (*Regexp) FindSubmatch
func (re *Regexp) FindSubmatch(b []byte) [][]byte
FindSubmatch returns a slice of slices holding the text of the leftmost match of the regular expression in b and the matches, if any, of its subexpressions, as defined by the 'Submatch' descriptions in the package comment. A return value of nil indicates no match.
func (*Regexp) FindSubmatchIndex
func (re *Regexp) FindSubmatchIndex(b []byte) []int
FindSubmatchIndex returns a slice holding the index pairs identifying the leftmost match of the regular expression in b and the matches, if any, of its subexpressions, as defined by the 'Submatch' and 'Index' descriptions in the package comment. A return value of nil indicates no match.
func (*Regexp) Match
func (re *Regexp) Match(b []byte) bool
Match returns whether the Regexp matches the byte slice b. The return value is a boolean: true for match, false for no match.
func (*Regexp) MatchString
func (re *Regexp) MatchString(s string) bool
MatchString returns whether the Regexp matches the string s. The return value is a boolean: true for match, false for no match.
func (*Regexp) NumSubexp
func (re *Regexp) NumSubexp() int
NumSubexp returns the number of parenthesized subexpressions in this Regexp.
func (*Regexp) ReplaceAll
func (re *Regexp) ReplaceAll(src, repl []byte) []byte
ReplaceAll returns a copy of src in which all matches for the Regexp have been replaced by repl. No support is provided for expressions (e.g. \1 or $1) in the replacement text.
func (*Regexp) ReplaceAllFunc
func (re *Regexp) ReplaceAllFunc(src []byte, repl func([]byte) []byte) []byte
ReplaceAllFunc returns a copy of src in which all matches for the Regexp have been replaced by the return value of of function repl (whose first argument is the matched []byte). No support is provided for expressions (e.g. \1 or $1) in the replacement string.
func (*Regexp) ReplaceAllString
func (re *Regexp) ReplaceAllString(src, repl string) string
ReplaceAllString returns a copy of src in which all matches for the Regexp have been replaced by repl. No support is provided for expressions (e.g. \1 or $1) in the replacement string.
func (*Regexp) ReplaceAllStringFunc
func (re *Regexp) ReplaceAllStringFunc(src string, repl func(string) string) string
ReplaceAllStringFunc returns a copy of src in which all matches for the Regexp have been replaced by the return value of of function repl (whose first argument is the matched string). No support is provided for expressions (e.g. \1 or $1) in the replacement string.