version: 1.10

package strings

import "strings"

Overview

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.

Index

Examples

Package files

builder.go compare.go reader.go replace.go search.go strings.go strings_amd64.go strings_decl.go

func Compare


  1. 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.


Example:

fmt.Println(strings.Compare(“a”, “b”))
fmt.Println(strings.Compare(“a”, “a”))
fmt.Println(strings.Compare(“b”, “a”))
// Output:
// -1
// 0
// 1

func Contains


  1. func Contains(s, substr string) bool


Contains reports whether substr is within s.


Example:

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


  1. func ContainsAny(s, chars string) bool


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


Example:

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


  1. func ContainsRune(s string, r rune) bool


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


Example:

// 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))
// Output:
// true
// false

func Count


  1. 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.


Example:

fmt.Println(strings.Count(“cheese”, “e”))
fmt.Println(strings.Count(“five”, “”)) // before & after each rune
// Output:
// 3
// 5

func EqualFold


  1. func EqualFold(s, t string) bool


EqualFold reports whether s and t, interpreted as UTF-8 strings, are equal under
Unicode case-folding.


Example:

fmt.Println(strings.EqualFold(“Go”, “go”))
// Output: true

func Fields


  1. 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.


Example:

fmt.Printf(“Fields are: %q”, strings.Fields(“ foo bar baz “))
// Output: Fields are: [“foo” “bar” “baz”]

func FieldsFunc


  1. 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). If f does not return
consistent results for a given c, FieldsFunc may crash.


Example:

f := func(c rune) bool {
return !unicode.IsLetter(c) && !unicode.IsNumber(c)
}
fmt.Printf(“Fields are: %q”, strings.FieldsFunc(“ foo1;bar2,baz3…”, f))
// Output: Fields are: [“foo1” “bar2” “baz3”]

func HasPrefix


  1. func HasPrefix(s, prefix string) bool


HasPrefix tests whether the string s begins with prefix.


Example:

fmt.Println(strings.HasPrefix(“Gopher”, “Go”))
fmt.Println(strings.HasPrefix(“Gopher”, “C”))
fmt.Println(strings.HasPrefix(“Gopher”, “”))
// Output:
// true
// false
// true

func HasSuffix


  1. func HasSuffix(s, suffix string) bool


HasSuffix tests whether the string s ends with suffix.


Example:

fmt.Println(strings.HasSuffix(“Amigo”, “go”))
fmt.Println(strings.HasSuffix(“Amigo”, “O”))
fmt.Println(strings.HasSuffix(“Amigo”, “Ami”))
fmt.Println(strings.HasSuffix(“Amigo”, “”))
// Output:
// true
// false
// false
// true

func Index


  1. 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.


Example:

fmt.Println(strings.Index(“chicken”, “ken”))
fmt.Println(strings.Index(“chicken”, “dmr”))
// Output:
// 4
// -1

func IndexAny


  1. 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.


Example:

fmt.Println(strings.IndexAny(“chicken”, “aeiouy”))
fmt.Println(strings.IndexAny(“crwth”, “aeiouy”))
// Output:
// 2
// -1

func IndexByte


  1. 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.


Example:

fmt.Println(strings.IndexByte(“golang”, ‘g’))
fmt.Println(strings.IndexByte(“gophers”, ‘h’))
fmt.Println(strings.IndexByte(“golang”, ‘x’))
// Output:
// 0
// 3
// -1

func IndexFunc


  1. 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.


Example:

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))
// Output:
// 7
// -1

func IndexRune


  1. 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.


Example:

fmt.Println(strings.IndexRune(“chicken”, ‘k’))
fmt.Println(strings.IndexRune(“chicken”, ‘d’))
// Output:
// 4
// -1

func Join


  1. 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:

s := []string{“foo”, “bar”, “baz”}
fmt.Println(strings.Join(s, “, “))
// Output: foo, bar, baz

func LastIndex


  1. 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.


Example:

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


  1. 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.


Example:

fmt.Println(strings.LastIndexAny(“go gopher”, “go”))
fmt.Println(strings.LastIndexAny(“go gopher”, “rodent”))
fmt.Println(strings.LastIndexAny(“go gopher”, “fail”))
// Output:
// 4
// 8
// -1

func LastIndexByte


  1. 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.


Example:

fmt.Println(strings.LastIndexByte(“Hello, world”, ‘l’))
fmt.Println(strings.LastIndexByte(“Hello, world”, ‘o’))
fmt.Println(strings.LastIndexByte(“Hello, world”, ‘x’))
// Output:
// 10
// 8
// -1

func LastIndexFunc


  1. 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.


Example:

fmt.Println(strings.LastIndexFunc(“go 123”, unicode.IsNumber))
fmt.Println(strings.LastIndexFunc(“123 go”, unicode.IsNumber))
fmt.Println(strings.LastIndexFunc(“go”, unicode.IsNumber))
// Output:
// 5
// 2
// -1

func Map


  1. 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:

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


  1. 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.


Example:

fmt.Println(“ba” + strings.Repeat(“na”, 2))
// Output: banana

func Replace


  1. 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.


Example:

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


  1. 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.


Example:

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


  1. 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.


Example:

fmt.Printf(“%q\n”, strings.SplitAfter(“a,b,c”, “,”))
// Output: [“a,” “b,” “c”]

func SplitAfterN


  1. 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.


Example:

fmt.Printf(“%q\n”, strings.SplitAfterN(“a,b,c”, “,”, 2))
// Output: [“a,” “b,c”]

func SplitN


  1. 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.


Example:

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


  1. 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.

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


Example:

fmt.Println(strings.Title(“her royal highness”))
// Output: Her Royal Highness

func ToLower


  1. func ToLower(s string) string


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


Example:

fmt.Println(strings.ToLower(“Gopher”))
// Output: gopher

func ToLowerSpecial


  1. 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, giving priority to the special casing rules.


Example:

fmt.Println(strings.ToLowerSpecial(unicode.TurkishCase, “Önnek İş”))
// Output: önnek iş

func ToTitle


  1. func ToTitle(s string) string


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


Example:

fmt.Println(strings.ToTitle(“loud noises”))
fmt.Println(strings.ToTitle(“хлеб”))
// Output:
// LOUD NOISES
// ХЛЕБ

func ToTitleSpecial


  1. func ToTitleSpecial(c 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.


Example:

fmt.Println(strings.ToTitleSpecial(unicode.TurkishCase, “dünyanın ilk borsa yapısı Aizonai kabul edilir”))
// Output:
// DÜNYANIN İLK BORSA YAPISI AİZONAİ KABUL EDİLİR

func ToUpper


  1. func ToUpper(s string) string


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


Example:

fmt.Println(strings.ToUpper(“Gopher”))
// Output: GOPHER

func ToUpperSpecial


  1. 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, giving priority to the special casing rules.


Example:

fmt.Println(strings.ToUpperSpecial(unicode.TurkishCase, “örnek iş”))
// Output: ÖRNEK İŞ

func Trim


  1. 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:

fmt.Print(strings.Trim(“¡¡¡Hello, Gophers!!!”, “!¡”))
// Output: Hello, Gophers

func TrimFunc


  1. 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.


Example:

fmt.Print(strings.TrimFunc(“¡¡¡Hello, Gophers!!!”, func(r rune) bool {
return !unicode.IsLetter(r) && !unicode.IsNumber(r)
}))
// Output: Hello, Gophers

func TrimLeft


  1. 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.


Example:

fmt.Print(strings.TrimLeft(“¡¡¡Hello, Gophers!!!”, “!¡”))
// Output: Hello, Gophers!!!

func TrimLeftFunc


  1. 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.


Example:

fmt.Print(strings.TrimLeftFunc(“¡¡¡Hello, Gophers!!!”, func(r rune) bool {
return !unicode.IsLetter(r) && !unicode.IsNumber(r)
}))
// Output: Hello, Gophers!!!

func TrimPrefix


  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.


Example:

var s = “¡¡¡Hello, Gophers!!!”
s = strings.TrimPrefix(s, “¡¡¡Hello, “)
s = strings.TrimPrefix(s, “¡¡¡Howdy, “)
fmt.Print(s)
// Output: Gophers!!!

func TrimRight


  1. 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.


Example:

fmt.Print(strings.TrimRight(“¡¡¡Hello, Gophers!!!”, “!¡”))
// Output: ¡¡¡Hello, Gophers

func TrimRightFunc


  1. 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.


Example:

fmt.Print(strings.TrimRightFunc(“¡¡¡Hello, Gophers!!!”, func(r rune) bool {
return !unicode.IsLetter(r) && !unicode.IsNumber(r)
}))
// Output: ¡¡¡Hello, Gophers

func TrimSpace


  1. 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:

fmt.Println(strings.TrimSpace(“ \t\n Hello, Gophers \n\t\r\n”))
// Output: Hello, Gophers

func TrimSuffix


  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.


Example:

var s = “¡¡¡Hello, Gophers!!!”
s = strings.TrimSuffix(s, “, Gophers!!!”)
s = strings.TrimSuffix(s, “, Marmots!!!”)
fmt.Print(s)
// Output: ¡¡¡Hello

type Builder


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


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.


Example:

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

// Output: 3…2…1…ignition

func (Builder) Grow


  1. 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. func (b Builder) Len() int


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

func (Builder) Reset


  1. func (b Builder) Reset()


Reset resets the Builder to be empty.

func (Builder) String


  1. func (b Builder) String() string


String returns the accumulated string.

func (Builder) Write


  1. 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. 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. 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. 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


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


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

func NewReader


  1. 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


  1. func (r Reader) Len() int


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

func (Reader) Read


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



func (Reader) ReadAt


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



func (Reader) ReadByte


  1. func (r Reader) ReadByte() (byte, error)



func (Reader) ReadRune


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



func (Reader) Reset


  1. func (r Reader) Reset(s string)


Reset resets the Reader to be reading from s.

func (Reader) Seek


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


Seek implements the io.Seeker interface.

func (Reader) Size


  1. 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


  1. func (r Reader) UnreadByte() error



func (Reader) UnreadRune


  1. func (r Reader) UnreadRune() error



func (Reader) WriteTo


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


WriteTo implements the io.WriterTo interface.

type Replacer


  1. 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.

func NewReplacer


  1. 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:

r := strings.NewReplacer(“<”, “<”, “>”, “>”)
fmt.Println(r.Replace(“This is HTML!”))
// Output: This is <b>HTML</b>!

func (Replacer) Replace


  1. func (r Replacer) Replace(s string) string


Replace returns a copy of s with all replacements performed.

func (Replacer) WriteString


  1. 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.