Package strings

func Compare ¶ 1.5

func Compare(a, 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.

Compare is included only for symmetry with package bytes. It is usually clearer and always faster to use the built-in string comparison operators ==, <, >, and so on.

fmt.Println(strings.Compare("a", "b"))
fmt.Println(strings.Compare("a", "a"))
fmt.Println(strings.Compare("b", "a"))

-1
0
1

func Contains ¶

func Contains(s, substr string) bool

Contains reports whether substr is within s.

fmt.Println(strings.Contains("seafood", "foo"))
fmt.Println(strings.Contains("seafood", "bar"))
fmt.Println(strings.Contains("seafood", ""))
fmt.Println(strings.Contains("", ""))

true
false
true
true

func ContainsAny ¶

func ContainsAny(s, chars string) bool

ContainsAny reports whether any Unicode code points in chars are within s.

fmt.Println(strings.ContainsAny("team", "i"))
fmt.Println(strings.ContainsAny("fail", "ui"))
fmt.Println(strings.ContainsAny("ure", "ui"))
fmt.Println(strings.ContainsAny("failure", "ui"))
fmt.Println(strings.ContainsAny("foo", ""))
fmt.Println(strings.ContainsAny("", ""))

false
true
true
true
false
false

func ContainsRune ¶

func ContainsRune(s string, r rune) bool

ContainsRune reports whether the Unicode code point r is within s.

// Finds whether a string contains a particular Unicode code point.
// The code point for the lowercase letter "a", for example, is 97.
fmt.Println(strings.ContainsRune("aardvark", 97))
fmt.Println(strings.ContainsRune("timeout", 97))

true
false

func Count ¶

func Count(s, 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.

fmt.Println(strings.Count("cheese", "e"))
fmt.Println(strings.Count("five", "")) // before & after each rune

3
5

func EqualFold ¶

func EqualFold(s, t string) bool

EqualFold reports whether s and t, interpreted as UTF-8 strings, are equal under Unicode case-folding, which is a more general form of case-insensitivity.

fmt.Println(strings.EqualFold("Go", "go"))

true

func Fields ¶

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.

fmt.Printf("Fields are: %q", strings.Fields("	foo bar	baz	 "))

Fields are: ["foo" "bar" "baz"]

func FieldsFunc ¶

func FieldsFunc(s string, f func(rune) bool) []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.

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.

f := func(c rune) bool {
		return !unicode.IsLetter(c) && !unicode.IsNumber(c)
}
fmt.Printf("Fields are: %q", strings.FieldsFunc("	foo1;bar2,baz3...", f))

Fields are: ["foo1" "bar2" "baz3"]

func HasPrefix ¶

func HasPrefix(s, prefix string) bool

HasPrefix tests whether the string s begins with prefix.

fmt.Println(strings.HasPrefix("Gopher", "Go"))
fmt.Println(strings.HasPrefix("Gopher", "C"))
fmt.Println(strings.HasPrefix("Gopher", ""))

true
false
true

func HasSuffix ¶

func HasSuffix(s, suffix string) bool

HasSuffix tests whether the string s ends with suffix.

fmt.Println(strings.HasSuffix("Amigo", "go"))
fmt.Println(strings.HasSuffix("Amigo", "O"))
fmt.Println(strings.HasSuffix("Amigo", "Ami"))
fmt.Println(strings.HasSuffix("Amigo", ""))

true
false
false
true

func Index ¶

func Index(s, substr string) int

Index returns the index of the first instance of substr in s, or -1 if substr is not present in s.

fmt.Println(strings.Index("chicken", "ken"))
fmt.Println(strings.Index("chicken", "dmr"))

4
-1

func IndexAny ¶

func IndexAny(s, 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.

fmt.Println(strings.IndexAny("chicken", "aeiouy"))
fmt.Println(strings.IndexAny("crwth", "aeiouy"))

2
-1

func IndexByte ¶ 1.2

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.

fmt.Println(strings.IndexByte("golang", 'g'))
fmt.Println(strings.IndexByte("gophers", 'h'))
fmt.Println(strings.IndexByte("golang", 'x'))

0
3
-1

func IndexFunc ¶

func IndexFunc(s string, f func(rune) bool) int

IndexFunc returns the index into s of the first Unicode code point satisfying f(c), or -1 if none do.

f := func(c rune) bool {
		return unicode.Is(unicode.Han, c)
}
fmt.Println(strings.IndexFunc("Hello, 世界", f))
fmt.Println(strings.IndexFunc("Hello, world", f))

7
-1

func IndexRune ¶

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.

fmt.Println(strings.IndexRune("chicken", 'k'))
fmt.Println(strings.IndexRune("chicken", 'd'))

4
-1

func Join ¶

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.

s := []string{"foo", "bar", "baz"}
fmt.Println(strings.Join(s, ", "))

foo, bar, baz

func LastIndex ¶

func LastIndex(s, substr string) int

LastIndex returns the index of the last instance of substr in s, or -1 if substr is not present in s.

fmt.Println(strings.Index("go gopher", "go"))
fmt.Println(strings.LastIndex("go gopher", "go"))
fmt.Println(strings.LastIndex("go gopher", "rodent"))

0
3
-1

func LastIndexAny ¶

func LastIndexAny(s, 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.

fmt.Println(strings.LastIndexAny("go gopher", "go"))
fmt.Println(strings.LastIndexAny("go gopher", "rodent"))
fmt.Println(strings.LastIndexAny("go gopher", "fail"))

4
8
-1

func LastIndexByte ¶ 1.5

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.

fmt.Println(strings.LastIndexByte("Hello, world", 'l'))
fmt.Println(strings.LastIndexByte("Hello, world", 'o'))
fmt.Println(strings.LastIndexByte("Hello, world", 'x'))

10
8
-1

func LastIndexFunc ¶

func LastIndexFunc(s string, f func(rune) bool) int

LastIndexFunc returns the index into s of the last Unicode code point satisfying f(c), or -1 if none do.

fmt.Println(strings.LastIndexFunc("go 123", unicode.IsNumber))
fmt.Println(strings.LastIndexFunc("123 go", unicode.IsNumber))
fmt.Println(strings.LastIndexFunc("go", unicode.IsNumber))

5
2
-1

func Map ¶

func Map(mapping func(rune) rune, 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.

rot13 := func(r rune) rune {
		switch {
		case r >= 'A' && r <= 'Z':
				return 'A' + (r-'A'+13)%26
		case r >= 'a' && r <= 'z':
				return 'a' + (r-'a'+13)%26
		}
		return r
}
fmt.Println(strings.Map(rot13, "'Twas brillig and the slithy gopher..."))

'Gjnf oevyyvt naq gur fyvgul tbcure...

func Repeat ¶

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.

fmt.Println("ba" + strings.Repeat("na", 2))

banana

func Replace ¶

func Replace(s, old, 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.

fmt.Println(strings.Replace("oink oink oink", "k", "ky", 2))
fmt.Println(strings.Replace("oink oink oink", "oink", "moo", -1))

oinky oinky oink
moo moo moo

func ReplaceAll ¶ 1.12

func ReplaceAll(s, old, 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.

fmt.Println(strings.ReplaceAll("oink oink oink", "oink", "moo"))

moo moo moo

func Split ¶

func Split(s, 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.

fmt.Printf("%q\n", strings.Split("a,b,c", ","))
fmt.Printf("%q\n", strings.Split("a man a plan a canal panama", "a "))
fmt.Printf("%q\n", strings.Split(" xyz ", ""))
fmt.Printf("%q\n", strings.Split("", "Bernardo O'Higgins"))

["a" "b" "c"]
["" "man " "plan " "canal panama"]
[" " "x" "y" "z" " "]
[""]

func SplitAfter ¶

func SplitAfter(s, 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.

fmt.Printf("%q\n", strings.SplitAfter("a,b,c", ","))

["a," "b," "c"]

func SplitAfterN ¶

func SplitAfterN(s, 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.

fmt.Printf("%q\n", strings.SplitAfterN("a,b,c", ",", 2))

["a," "b,c"]

func SplitN ¶

func SplitN(s, 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.

fmt.Printf("%q\n", strings.SplitN("a,b,c", ",", 2))
z := strings.SplitN("a,b,c", ",", 0)
fmt.Printf("%q (nil = %v)\n", z, z == nil)

["a" "b,c"]
[] (nil = true)

func Title ¶

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.

BUG(rsc): The rule Title uses for word boundaries does not handle Unicode punctuation properly.

// Compare this example to the ToTitle example.
fmt.Println(strings.Title("her royal highness"))
fmt.Println(strings.Title("loud noises"))
fmt.Println(strings.Title("хлеб"))

Her Royal Highness
Loud Noises
Хлеб

func ToLower ¶

func ToLower(s string) string

ToLower returns s with all Unicode letters mapped to their lower case.

fmt.Println(strings.ToLower("Gopher"))

gopher

func ToLowerSpecial ¶

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.

fmt.Println(strings.ToLowerSpecial(unicode.TurkishCase, "Önnek İş"))

önnek iş

func ToTitle ¶

func ToTitle(s string) string

ToTitle returns a copy of the string s with all Unicode letters mapped to their Unicode title case.

// Compare this example to the Title example.
fmt.Println(strings.ToTitle("her royal highness"))
fmt.Println(strings.ToTitle("loud noises"))
fmt.Println(strings.ToTitle("хлеб"))

HER ROYAL HIGHNESS
LOUD NOISES
ХЛЕБ

func ToTitleSpecial ¶

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.

fmt.Println(strings.ToTitleSpecial(unicode.TurkishCase, "dünyanın ilk borsa yapısı Aizonai kabul edilir"))

DÜNYANIN İLK BORSA YAPISI AİZONAİ KABUL EDİLİR

func ToUpper ¶

func ToUpper(s string) string

ToUpper returns s with all Unicode letters mapped to their upper case.

fmt.Println(strings.ToUpper("Gopher"))

GOPHER

func ToUpperSpecial ¶

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.

fmt.Println(strings.ToUpperSpecial(unicode.TurkishCase, "örnek iş"))

ÖRNEK İŞ

func ToValidUTF8 ¶ 1.13

func ToValidUTF8(s, 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.

func Trim ¶

func Trim(s, cutset string) string

Trim returns a slice of the string s with all leading and trailing Unicode code points contained in cutset removed.

fmt.Print(strings.Trim("¡¡¡Hello, Gophers!!!", "!¡"))

Hello, Gophers

func TrimFunc ¶

func TrimFunc(s string, f func(rune) bool) string

TrimFunc returns a slice of the string s with all leading and trailing Unicode code points c satisfying f(c) removed.

fmt.Print(strings.TrimFunc("¡¡¡Hello, Gophers!!!", func(r rune) bool {
		return !unicode.IsLetter(r) && !unicode.IsNumber(r)
}))

Hello, Gophers

func TrimLeft ¶

func TrimLeft(s, 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.

fmt.Print(strings.TrimLeft("¡¡¡Hello, Gophers!!!", "!¡"))

Hello, Gophers!!!

func TrimLeftFunc ¶

func TrimLeftFunc(s string, f func(rune) bool) string

TrimLeftFunc returns a slice of the string s with all leading Unicode code points c satisfying f(c) removed.

fmt.Print(strings.TrimLeftFunc("¡¡¡Hello, Gophers!!!", func(r rune) bool {
		return !unicode.IsLetter(r) && !unicode.IsNumber(r)
}))

Hello, Gophers!!!

func TrimPrefix ¶ 1.1

func TrimPrefix(s, prefix string) string

TrimPrefix returns s without the provided leading prefix string. If s doesn't start with prefix, s is returned unchanged.

var s = "¡¡¡Hello, Gophers!!!"
s = strings.TrimPrefix(s, "¡¡¡Hello, ")
s = strings.TrimPrefix(s, "¡¡¡Howdy, ")
fmt.Print(s)

Gophers!!!

func TrimRight ¶

func TrimRight(s, 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.

fmt.Print(strings.TrimRight("¡¡¡Hello, Gophers!!!", "!¡"))

¡¡¡Hello, Gophers

func TrimRightFunc ¶

func TrimRightFunc(s string, f func(rune) bool) string

TrimRightFunc returns a slice of the string s with all trailing Unicode code points c satisfying f(c) removed.

fmt.Print(strings.TrimRightFunc("¡¡¡Hello, Gophers!!!", func(r rune) bool {
		return !unicode.IsLetter(r) && !unicode.IsNumber(r)
}))

¡¡¡Hello, Gophers

func TrimSpace ¶

func TrimSpace(s string) string

TrimSpace returns a slice of the string s, with all leading and trailing white space removed, as defined by Unicode.

fmt.Println(strings.TrimSpace(" \t\n Hello, Gophers \n\t\r\n"))

Hello, Gophers

func TrimSuffix ¶ 1.1

func TrimSuffix(s, suffix string) string

TrimSuffix returns s without the provided trailing suffix string. If s doesn't end with suffix, s is returned unchanged.

var s = "¡¡¡Hello, Gophers!!!"
s = strings.TrimSuffix(s, ", Gophers!!!")
s = strings.TrimSuffix(s, ", Marmots!!!")
fmt.Print(s)

¡¡¡Hello

type Builder ¶ 1.10

A Builder is used to efficiently build a string using Write methods. It minimizes memory copying. The zero value is ready to use. Do not copy a non-zero Builder.

type Builder struct {
		// contains filtered or unexported fields
}

var b strings.Builder
for i := 3; i >= 1; i-- {
		fmt.Fprintf(&b, "%d...", i)
}
b.WriteString("ignition")
fmt.Println(b.String())

3...2...1...ignition

func (*Builder) Cap ¶ 1.12

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.

func (*Builder) Grow ¶ 1.10

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.

func (*Builder) Len ¶ 1.10

func (b *Builder) Len() int

Len returns the number of accumulated bytes; b.Len() == len(b.String()).

func (*Builder) Reset ¶ 1.10

func (b *Builder) Reset()

Reset resets the Builder to be empty.

func (*Builder) String ¶ 1.10

func (b *Builder) String() string

String returns the accumulated string.

func (*Builder) Write ¶ 1.10

func (b *Builder) Write(p []byte) (int, error)

Write appends the contents of p to b's buffer. Write always returns len(p), nil.

func (*Builder) WriteByte ¶ 1.10

func (b *Builder) WriteByte(c byte) error

WriteByte appends the byte c to b's buffer. The returned error is always nil.

func (*Builder) WriteRune ¶ 1.10

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.

func (*Builder) WriteString ¶ 1.10

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.

type Reader ¶

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.

type Reader struct {
		// contains filtered or unexported fields
}

func NewReader ¶

func NewReader(s string) *Reader

NewReader returns a new Reader reading from s. It is similar to bytes.NewBufferString but more efficient and read-only.

func (*Reader) Len ¶

func (r *Reader) Len() int

Len returns the number of bytes of the unread portion of the string.

func (*Reader) Read ¶

func (r *Reader) Read(b []byte) (n int, err error)

Read implements the io.Reader interface.

func (*Reader) ReadAt ¶

func (r *Reader) ReadAt(b []byte, off int64) (n int, err error)

ReadAt implements the io.ReaderAt interface.

func (*Reader) ReadByte ¶

func (r *Reader) ReadByte() (byte, error)

ReadByte implements the io.ByteReader interface.

func (*Reader) ReadRune ¶

func (r *Reader) ReadRune() (ch rune, size int, err error)

ReadRune implements the io.RuneReader interface.

func (*Reader) Reset ¶ 1.7

func (r *Reader) Reset(s string)

Reset resets the Reader to be reading from s.

func (*Reader) Seek ¶

func (r *Reader) Seek(offset int64, whence int) (int64, error)

Seek implements the io.Seeker interface.

func (*Reader) Size ¶ 1.5

func (r *Reader) Size() int64

Size returns the original length of the underlying string. Size is the number of bytes available for reading via ReadAt. The returned value is always the same and is not affected by calls to any other method.

func (*Reader) UnreadByte ¶

func (r *Reader) UnreadByte() error

UnreadByte implements the io.ByteScanner interface.

func (*Reader) UnreadRune ¶

func (r *Reader) UnreadRune() error

UnreadRune implements the io.RuneScanner interface.

func (*Reader) WriteTo ¶ 1.1

func (r *Reader) WriteTo(w io.Writer) (n int64, err error)

WriteTo implements the io.WriterTo interface.

type Replacer ¶

Replacer replaces a list of strings with replacements. It is safe for concurrent use by multiple goroutines.

type Replacer struct {
		// contains filtered or unexported fields
}

func NewReplacer ¶

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.

r := strings.NewReplacer("<", "&lt;", ">", "&gt;")
fmt.Println(r.Replace("This is <b>HTML</b>!"))

This is <b>HTML</b>!

func (*Replacer) Replace ¶

func (r *Replacer) Replace(s string) string

Replace returns a copy of s with all replacements performed.

func (*Replacer) WriteString ¶

func (r *Replacer) WriteString(w io.Writer, s string) (n int, err error)

WriteString writes s to w with all replacements performed.

Bugs

• ☞

  The rule Title uses for word boundaries does not handle Unicode punctuation properly.