strings
import "strings"
Package strings implements simple functions to manipulate UTF-8 encoded strings. For information about UTF-8 strings in Go, see https://blog.golang.org/strings.
Go 1.26.1
Functions
func Clone(s string) string
Clone returns a fresh copy of s. It guarantees to make a copy of s into a new allocation, which can be important when retaining only a small substring of a much larger string. Using Clone can help such programs use less memory. Of course, since using Clone makes a copy, overuse of Clone can make programs use more memory. Clone should typically be used only rarely, and only when profiling indicates that it is needed. For strings of length zero the string "" will be returned and no allocation i...
strings/clone.go:21
func Compare(a string, b string) int
Compare returns an integer comparing two strings lexicographically. The result will be 0 if a == b, -1 if a < b, and +1 if a > b. Use Compare when you need to perform a three-way comparison (with [slices.SortFunc], for example). It is usually clearer and always faster to use the built-in string comparison operators ==, <, >, and so on.
strings/compare.go:15
func Contains(s string, substr string) bool
Contains reports whether substr is within s.
strings/strings.go:62
func ContainsAny(s string, chars string) bool
ContainsAny reports whether any Unicode code points in chars are within s.
strings/strings.go:67
func ContainsFunc(s string, f func(...)) bool
ContainsFunc reports whether any Unicode code points r within s satisfy f(r).
strings/strings.go:77
func ContainsRune(s string, r rune) bool
ContainsRune reports whether the Unicode code point r is within s.
strings/strings.go:72
func Count(s string, substr string) int
Count counts the number of non-overlapping instances of substr in s. If substr is an empty string, Count returns 1 + the number of Unicode code points in s.
strings/strings.go:42
func Cut(s string, sep string) (string, bool)
Cut slices s around the first instance of sep, returning the text before and after sep. The found result reports whether sep appears in s. If sep does not appear in s, cut returns s, "", false.
strings/strings.go:1273
func CutPrefix(s string, prefix string) (string, bool)
CutPrefix returns s without the provided leading prefix string and reports whether it found the prefix. If s doesn't start with prefix, CutPrefix returns s, false. If prefix is the empty string, CutPrefix returns s, true.
strings/strings.go:1281
func CutSuffix(s string, suffix string) (string, bool)
CutSuffix returns s without the provided ending suffix string and reports whether it found the suffix. If s doesn't end with suffix, CutSuffix returns s, false. If suffix is the empty string, CutSuffix returns s, true.
strings/strings.go:1289
func EqualFold(s string, t string) bool
EqualFold reports whether s and t, interpreted as UTF-8 strings, are equal under simple Unicode case-folding, which is a more general form of case-insensitivity.
strings/strings.go:1187
func Fields(s string) []string
Fields splits the string s around each instance of one or more consecutive white space characters, as defined by [unicode.IsSpace], returning a slice of substrings of s or an empty slice if s contains only white space. Every element of the returned slice is non-empty. Unlike [Split], leading and trailing runs of white space characters are discarded.
strings/strings.go:384
func FieldsFunc(s string, f func(...)) []string
FieldsFunc splits the string s at each run of Unicode code points c satisfying f(c) and returns an array of slices of s. If all code points in s satisfy f(c) or the string is empty, an empty slice is returned. Every element of the returned slice is non-empty. Unlike [Split], leading and trailing runs of code points satisfying f(c) are discarded. FieldsFunc makes no guarantees about the order in which it calls f(c) and assumes that f always returns the same value for a given c.
strings/strings.go:441
func FieldsFuncSeq(s string, f func(...)) interface{}FieldsFuncSeq returns an iterator over substrings of s split around runs of Unicode code points satisfying f(c). The iterator yields the same strings that would be returned by [FieldsFunc](s), but without constructing the slice.
strings/iter.go:116
func FieldsSeq(s string) interface{}FieldsSeq returns an iterator over substrings of s split around runs of whitespace characters, as defined by [unicode.IsSpace]. The iterator yields the same strings that would be returned by [Fields](s), but without constructing the slice.
strings/iter.go:83
func HasPrefix(s string, prefix string) bool
HasPrefix reports whether the string s begins with prefix.
strings/strings.go:520
func HasSuffix(s string, suffix string) bool
HasSuffix reports whether the string s ends with suffix.
strings/strings.go:525
func Index(s string, substr string) int
Index returns the index of the first instance of substr in s, or -1 if substr is not present in s.
strings/strings.go:1265
func IndexAny(s string, chars string) int
IndexAny returns the index of the first instance of any Unicode code point from chars in s, or -1 if no Unicode code point from chars is present in s.
strings/strings.go:201
func IndexByte(s string, c byte) int
IndexByte returns the index of the first instance of c in s, or -1 if c is not present in s.
strings/strings.go:119
func IndexFunc(s string, f func(...)) int
IndexFunc returns the index into s of the first Unicode code point satisfying f(c), or -1 if none do.
strings/strings.go:916
func IndexRune(s string, r rune) int
IndexRune returns the index of the first instance of the Unicode code point r, or -1 if rune is not present in s. If r is [utf8.RuneError], it returns the first instance of any invalid UTF-8 byte sequence.
strings/strings.go:127
func Join(elems []string, sep string) string
Join concatenates the elements of its first argument to create a single string. The separator string sep is placed between elements in the resulting string.
strings/strings.go:487
func LastIndex(s string, substr string) int
LastIndex returns the index of the last instance of substr in s, or -1 if substr is not present in s.
strings/strings.go:82
func LastIndexAny(s string, chars string) int
LastIndexAny returns the index of the last instance of any Unicode code point from chars in s, or -1 if no Unicode code point from chars is present in s.
strings/strings.go:235
func LastIndexByte(s string, c byte) int
LastIndexByte returns the index of the last instance of c in s, or -1 if c is not present in s.
strings/strings.go:285
func LastIndexFunc(s string, f func(...)) int
LastIndexFunc returns the index into s of the last Unicode code point satisfying f(c), or -1 if none do.
strings/strings.go:922
func Lines(s string) interface{}Lines returns an iterator over the newline-terminated lines in the string s. The lines yielded by the iterator include their terminating newlines. If s is empty, the iterator yields no lines at all. If s does not end in a newline, the final yielded line will not end in a newline. It returns a single-use iterator.
strings/iter.go:18
func Map(mapping func(...), s string) string
Map returns a copy of the string s with all its characters modified according to the mapping function. If mapping returns a negative value, the character is dropped from the string with no replacement.
strings/strings.go:532
func NewReader(s string) *Reader
NewReader returns a new [Reader] reading from s. It is similar to [bytes.NewBufferString] but more efficient and non-writable.
strings/reader.go:156
func NewReplacer(oldnew ...string) *Replacer
NewReplacer returns a new [Replacer] from a list of old, new string pairs. Replacements are performed in the order they appear in the target string, without overlapping matches. The old string comparisons are done in argument order. NewReplacer panics if given an odd number of arguments.
strings/replace.go:32
func Repeat(s string, count int) string
Repeat returns a new string consisting of count copies of the string s. It panics if count is negative or if the result of (len(s) * count) overflows.
strings/strings.go:616
func Replace(s string, old string, new string, n int) string
Replace returns a copy of the string s with the first n non-overlapping instances of old replaced by new. If old is empty, it matches at the beginning of the string and after each UTF-8 sequence, yielding up to k+1 replacements for a k-rune string. If n < 0, there is no limit on the number of replacements.
strings/strings.go:1138
func ReplaceAll(s string, old string, new string) string
ReplaceAll returns a copy of the string s with all non-overlapping instances of old replaced by new. If old is empty, it matches at the beginning of the string and after each UTF-8 sequence, yielding up to k+1 replacements for a k-rune string.
strings/strings.go:1180
func Split(s string, sep string) []string
Split slices s into all substrings separated by sep and returns a slice of the substrings between those separators. If s does not contain sep and sep is not empty, Split returns a slice of length 1 whose only element is s. If sep is empty, Split splits after each UTF-8 sequence. If both s and sep are empty, Split returns an empty slice. It is equivalent to [SplitN] with a count of -1. To split around the first instance of a separator, see [Cut].
strings/strings.go:361
func SplitAfter(s string, sep string) []string
SplitAfter slices s into all substrings after each instance of sep and returns a slice of those substrings. If s does not contain sep and sep is not empty, SplitAfter returns a slice of length 1 whose only element is s. If sep is empty, SplitAfter splits after each UTF-8 sequence. If both s and sep are empty, SplitAfter returns an empty slice. It is equivalent to [SplitAfterN] with a count of -1.
strings/strings.go:373
func SplitAfterN(s string, sep string, n int) []string
SplitAfterN slices s into substrings after each instance of sep and returns a slice of those substrings. The count determines the number of substrings to return: - n > 0: at most n substrings; the last substring will be the unsplit remainder; - n == 0: the result is nil (zero substrings); - n < 0: all substrings. Edge cases for s and sep (for example, empty strings) are handled as described in the documentation for [SplitAfter].
strings/strings.go:345
func SplitAfterSeq(s string, sep string) interface{}SplitAfterSeq returns an iterator over substrings of s split after each instance of sep. The iterator yields the same strings that would be returned by [SplitAfter](s, sep), but without constructing the slice. It returns a single-use iterator.
strings/iter.go:75
func SplitN(s string, sep string, n int) []string
SplitN slices s into substrings separated by sep and returns a slice of the substrings between those separators. The count determines the number of substrings to return: - n > 0: at most n substrings; the last substring will be the unsplit remainder; - n == 0: the result is nil (zero substrings); - n < 0: all substrings. Edge cases for s and sep (for example, empty strings) are handled as described in the documentation for [Split]. To split around the first instance of a separator, s...
strings/strings.go:333
func SplitSeq(s string, sep string) interface{}SplitSeq returns an iterator over all substrings of s separated by sep. The iterator yields the same strings that would be returned by [Split](s, sep), but without constructing the slice. It returns a single-use iterator.
strings/iter.go:67
func Title(s string) string
Title returns a copy of the string s with all Unicode letters that begin words mapped to their Unicode title case. Deprecated: The rule Title uses for word boundaries does not handle Unicode punctuation properly. Use golang.org/x/text/cases instead.
strings/strings.go:868
func ToLower(s string) string
ToLower returns s with all Unicode letters mapped to their lower case.
strings/strings.go:727
func ToLowerSpecial(c unicode.SpecialCase, s string) string
ToLowerSpecial returns a copy of the string s with all Unicode letters mapped to their lower case using the case mapping specified by c.
strings/strings.go:778
func ToTitle(s string) string
ToTitle returns a copy of the string s with all Unicode letters mapped to their Unicode title case.
strings/strings.go:768
func ToTitleSpecial(c unicode.SpecialCase, s string) string
ToTitleSpecial returns a copy of the string s with all Unicode letters mapped to their Unicode title case, giving priority to the special casing rules.
strings/strings.go:784
func ToUpper(s string) string
ToUpper returns s with all Unicode letters mapped to their upper case.
strings/strings.go:687
func ToUpperSpecial(c unicode.SpecialCase, s string) string
ToUpperSpecial returns a copy of the string s with all Unicode letters mapped to their upper case using the case mapping specified by c.
strings/strings.go:772
func ToValidUTF8(s string, replacement string) string
ToValidUTF8 returns a copy of the string s with each run of invalid UTF-8 byte sequences replaced by the replacement string, which may be empty.
strings/strings.go:790
func Trim(s string, cutset string) string
Trim returns a slice of the string s with all leading and trailing Unicode code points contained in cutset removed.
strings/strings.go:982
func TrimFunc(s string, f func(...)) string
TrimFunc returns a slice of the string s with all leading and trailing Unicode code points c satisfying f(c) removed.
strings/strings.go:910
func TrimLeft(s string, cutset string) string
TrimLeft returns a slice of the string s with all leading Unicode code points contained in cutset removed. To remove a prefix, use [TrimPrefix] instead.
strings/strings.go:999
func TrimLeftFunc(s string, f func(...)) string
TrimLeftFunc returns a slice of the string s with all leading Unicode code points c satisfying f(c) removed.
strings/strings.go:887
func TrimPrefix(s string, prefix string) string
TrimPrefix returns s without the provided leading prefix string. If s doesn't start with prefix, s is returned unchanged.
strings/strings.go:1122
func TrimRight(s string, cutset string) string
TrimRight returns a slice of the string s, with all trailing Unicode code points contained in cutset removed. To remove a suffix, use [TrimSuffix] instead.
strings/strings.go:1044
func TrimRightFunc(s string, f func(...)) string
TrimRightFunc returns a slice of the string s with all trailing Unicode code points c satisfying f(c) removed.
strings/strings.go:897
func TrimSpace(s string) string
TrimSpace returns a slice (substring) of the string s, with all leading and trailing white space removed, as defined by Unicode.
strings/strings.go:1091
func TrimSuffix(s string, suffix string) string
TrimSuffix returns s without the provided trailing suffix string. If s doesn't end with suffix, s is returned unchanged.
strings/strings.go:1128
Types
type Builder struct {
// contains filtered or unexported fields
}A Builder is used to efficiently build a string using [Builder.Write] methods. It minimizes memory copying. The zero value is ready to use. Do not copy a non-zero Builder.
strings/builder.go:17
func (b *Builder) Cap() int
Cap returns the capacity of the builder's underlying byte slice. It is the total space allocated for the string being built and includes any bytes already written.
strings/builder.go:56
func (b *Builder) Grow(n int)
Grow grows b's capacity, if necessary, to guarantee space for another n bytes. After Grow(n), at least n bytes can be written to b without another allocation. If n is negative, Grow panics.
strings/builder.go:75
func (b *Builder) Len() int
Len returns the number of accumulated bytes; b.Len() == len(b.String()).
strings/builder.go:51
func (b *Builder) Reset()
Reset resets the [Builder] to be empty.
strings/builder.go:59
func (b *Builder) String() string
String returns the accumulated string.
strings/builder.go:46
func (b *Builder) Write(p []byte) (int, error)
Write appends the contents of p to b's buffer. Write always returns len(p), nil.
strings/builder.go:87
func (b *Builder) WriteByte(c byte) error
WriteByte appends the byte c to b's buffer. The returned error is always nil.
strings/builder.go:95
func (b *Builder) WriteRune(r rune) (int, error)
WriteRune appends the UTF-8 encoding of Unicode code point r to b's buffer. It returns the length of r and a nil error.
strings/builder.go:103
func (b *Builder) WriteString(s string) (int, error)
WriteString appends the contents of s to b's buffer. It returns the length of s and a nil error.
strings/builder.go:112
type Reader struct {
// contains filtered or unexported fields
}A Reader implements the [io.Reader], [io.ReaderAt], [io.ByteReader], [io.ByteScanner], [io.RuneReader], [io.RuneScanner], [io.Seeker], and [io.WriterTo] interfaces by reading from a string. The zero value for Reader operates like a Reader of an empty string.
strings/reader.go:17
func (r *Reader) Len() int
Len returns the number of bytes of the unread portion of the string.
strings/reader.go:25
func (r *Reader) Read(b []byte) (int, error)
Read implements the [io.Reader] interface.
strings/reader.go:39
func (r *Reader) ReadAt(b []byte, off int64) (int, error)
ReadAt implements the [io.ReaderAt] interface.
strings/reader.go:50
func (r *Reader) ReadByte() (byte, error)
ReadByte implements the [io.ByteReader] interface.
strings/reader.go:66
func (r *Reader) ReadRune() (rune, int, error)
ReadRune implements the [io.RuneReader] interface.
strings/reader.go:87
func (r *Reader) Reset(s string)
Reset resets the [Reader] to be reading from s.
strings/reader.go:152
func (r *Reader) Seek(offset int64, whence int) (int64, error)
Seek implements the [io.Seeker] interface.
strings/reader.go:112
func (r *Reader) Size() int64
Size returns the original length of the underlying string. Size is the number of bytes available for reading via [Reader.ReadAt]. The returned value is always the same and is not affected by calls to any other method.
strings/reader.go:36
func (r *Reader) UnreadByte() error
UnreadByte implements the [io.ByteScanner] interface.
strings/reader.go:77
func (r *Reader) UnreadRune() error
UnreadRune implements the [io.RuneScanner] interface.
strings/reader.go:99
func (r *Reader) WriteTo(w io.Writer) (int64, error)
WriteTo implements the [io.WriterTo] interface.
strings/reader.go:133
type Replacer struct {
// contains filtered or unexported fields
}Replacer replaces a list of strings with replacements. It is safe for concurrent use by multiple goroutines.
strings/replace.go:14
func (r *Replacer) Replace(s string) string
Replace returns a copy of s with all replacements performed.
strings/replace.go:95
func (r *Replacer) WriteString(w io.Writer, s string) (int, error)
WriteString writes s to w with all replacements performed.
strings/replace.go:101