strings - The Go Programming Language

Golang

Package strings

import "strings"
Overview
Index
Examples

Overview ?

Overview ?

Package strings implements simple functions to manipulate strings.

Index

func Contains(s, substr string) bool
func ContainsAny(s, chars string) bool
func ContainsRune(s string, r rune) bool
func Count(s, sep string) int
func EqualFold(s, t string) bool
func Fields(s string) []string
func FieldsFunc(s string, f func(rune) bool) []string
func HasPrefix(s, prefix string) bool
func HasSuffix(s, suffix string) bool
func Index(s, sep string) int
func IndexAny(s, chars string) int
func IndexFunc(s string, f func(rune) bool) int
func IndexRune(s string, r rune) int
func Join(a []string, sep string) string
func LastIndex(s, sep string) int
func LastIndexAny(s, chars string) int
func LastIndexFunc(s string, f func(rune) bool) int
func Map(mapping func(rune) rune, s string) string
func Repeat(s string, count int) string
func Replace(s, old, new string, n int) string
func Split(s, sep string) []string
func SplitAfter(s, sep string) []string
func SplitAfterN(s, sep string, n int) []string
func SplitN(s, sep string, n int) []string
func Title(s string) string
func ToLower(s string) string
func ToLowerSpecial(_case unicode.SpecialCase, s string) string
func ToTitle(s string) string
func ToTitleSpecial(_case unicode.SpecialCase, s string) string
func ToUpper(s string) string
func ToUpperSpecial(_case unicode.SpecialCase, s string) string
func Trim(s string, cutset string) string
func TrimFunc(s string, f func(rune) bool) string
func TrimLeft(s string, cutset string) string
func TrimLeftFunc(s string, f func(rune) bool) string
func TrimRight(s string, cutset string) string
func TrimRightFunc(s string, f func(rune) bool) string
func TrimSpace(s string) string
type Reader
    func NewReader(s string) *Reader
    func (r *Reader) Len() int
    func (r *Reader) Read(b []byte) (n int, err error)
    func (r *Reader) ReadAt(b []byte, off int64) (n int, err error)
    func (r *Reader) ReadByte() (b byte, err error)
    func (r *Reader) ReadRune() (ch rune, size int, err error)
    func (r *Reader) Seek(offset int64, whence int) (int64, error)
    func (r *Reader) UnreadByte() error
    func (r *Reader) UnreadRune() error
type Replacer
    func NewReplacer(oldnew ...string) *Replacer
    func (r *Replacer) Replace(s string) string
    func (r *Replacer) WriteString(w io.Writer, s string) (n int, err error)
Bugs

Examples

Contains
ContainsAny
Count
EqualFold
Fields
Index
IndexRune
Join
LastIndex
Map
NewReplacer
Repeat
Replace
Split
SplitAfter
SplitAfterN
SplitN
Title
ToLower
ToTitle
ToUpper
Trim
TrimSpace

Package files

reader.go replace.go strings.go

func Contains

func Contains(s, substr string) bool

Contains returns true if substr is within s.

? Example

? Example

Code:

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

Output:

true
false
true
true

func ContainsAny

func ContainsAny(s, chars string) bool

ContainsAny returns true if any Unicode code points in chars are within s.

? Example

? Example

Code:

fmt.Println(strings.ContainsAny("team", "i"))
fmt.Println(strings.ContainsAny("failure", "u & i"))
fmt.Println(strings.ContainsAny("foo", ""))
fmt.Println(strings.ContainsAny("", ""))

Output:

false
true
false
false

func ContainsRune

func ContainsRune(s string, r rune) bool

ContainsRune returns true if the Unicode code point r is within s.

func Count

func Count(s, sep string) int

Count counts the number of non-overlapping instances of sep in s.

? Example

? Example

Code:

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

Output:

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.

? Example

? Example

Code:

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

Output:

true

func Fields

func Fields(s string) []string

Fields splits the string s around each instance of one or more consecutive white space characters, returning an array of substrings of s or an empty list if s contains only white space.

? Example

? Example

Code:

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

Output:

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.

func HasPrefix

func HasPrefix(s, prefix string) bool

HasPrefix tests whether the string s begins with prefix.

func HasSuffix

func HasSuffix(s, suffix string) bool

HasSuffix tests whether the string s ends with suffix.

func Index

func Index(s, sep string) int

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

? Example

? Example

Code:

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

Output:

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.

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.

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.

? Example

? Example

Code:

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

Output:

4
-1

func Join

func Join(a []string, sep string) string

Join concatenates the elements of a to create a single string. The separator string sep is placed between elements in the resulting string.

? Example

? Example

Code:

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

Output:

foo, bar, baz

func LastIndex

func LastIndex(s, sep string) int

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

? Example

? Example

Code:

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

Output:

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.

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.

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.

? Example

? Example

Code:

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..."))

Output:

'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.

? Example

? Example

Code:

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

Output:

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 n < 0, there is no limit on the number of replacements.

? Example

? Example

Code:

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

Output:

oinky oinky oink
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 sep is empty, Split splits after each UTF-8 sequence. It is equivalent to SplitN with a count of -1.

? Example

? Example

Code:

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"))

Output:

["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 sep is empty, SplitAfter splits after each UTF-8 sequence. It is equivalent to SplitAfterN with a count of -1.

? Example

? Example

Code:

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

Output:

["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. If sep is empty, SplitAfterN splits after each UTF-8 sequence. 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

? Example

? Example

Code:

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

Output:

["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. If sep is empty, SplitN splits after each UTF-8 sequence. 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

? Example

? Example

Code:

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)

Output:

["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 title case.

? Example

? Example

Code:

fmt.Println(strings.Title("her royal highness"))

Output:

Her Royal Highness

func ToLower

func ToLower(s string) string

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

? Example

? Example

Code:

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

Output:

gopher

func ToLowerSpecial

func ToLowerSpecial(_case unicode.SpecialCase, s string) string

ToLowerSpecial returns a copy of the string s with all Unicode letters mapped to their lower case, giving priority to the special casing rules.

func ToTitle

func ToTitle(s string) string

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

? Example

? Example

Code:

fmt.Println(strings.ToTitle("loud noises"))
fmt.Println(strings.ToTitle("ݧ֧"))

Output:

LOUD NOISES

func ToTitleSpecial

func ToTitleSpecial(_case unicode.SpecialCase, s string) string

ToTitleSpecial returns a copy of the string s with all Unicode letters mapped to their title case, giving priority to the special casing rules.

func ToUpper

func ToUpper(s string) string

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

? Example

? Example

Code:

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

Output:

GOPHER

func ToUpperSpecial

func ToUpperSpecial(_case unicode.SpecialCase, s string) string

ToUpperSpecial returns a copy of the string s with all Unicode letters mapped to their upper case, giving priority to the special casing rules.

func Trim

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.

? Example

? Example

Code:

fmt.Printf("[%q]", strings.Trim(" !!! Achtung !!! ", "! "))

Output:

["Achtung"]

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.

func TrimLeft

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.

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.

func TrimRight

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.

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.

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.

? Example

? Example

Code:

fmt.Println(strings.TrimSpace(" \t\n a lone gopher \n\t\r\n"))

Output:

a lone gopher

type Reader

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

A Reader implements the io.Reader, io.ReaderAt, io.Seeker, io.ByteScanner, and io.RuneScanner interfaces by reading from a string.

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)

func (*Reader) ReadAt

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

func (*Reader) ReadByte

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

func (*Reader) ReadRune

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

func (*Reader) Seek

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

Seek implements the io.Seeker interface.

func (*Reader) UnreadByte

func (r *Reader) UnreadByte() error

func (*Reader) UnreadRune

func (r *Reader) UnreadRune() error

type Replacer

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

A Replacer replaces a list of strings with replacements.

func NewReplacer

func NewReplacer(oldnew ...string) *Replacer

NewReplacer returns a new Replacer from a list of old, new string pairs. Replacements are performed in order, without overlapping matches.

? Example

? Example

Code:

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

Output:

This is &lt;b&gt;HTML&lt;/b&gt;!

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.