Go: strings Index | Examples | Files

package 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.

Index

Examples

Package Files

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

func Compare Uses

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.

func Contains Uses

func Contains(s, substr string) bool

Contains reports whether substr is within s.

Code:play 

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 Uses

func ContainsAny(s, chars string) bool

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

Code:play 

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 Uses

func ContainsRune(s string, r rune) bool

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

func Count Uses

func Count(s, sep string) int

Count counts the number of non-overlapping instances of sep in s. If sep is an empty string, Count returns 1 + the number of Unicode code points in s.

Code:play 

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

Output:

3
5

func EqualFold Uses

func EqualFold(s, t string) bool

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

Code:play 

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

Output:

true

func Fields Uses

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 an array of substrings of s or an empty list if s contains only white space.

Code:play 

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

Output:

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

func FieldsFunc Uses

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.

Code:play 

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 Uses

func HasPrefix(s, prefix string) bool

HasPrefix tests whether the string s begins with prefix.

Code:play 

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

Output:

true
false
true

func HasSuffix Uses

func HasSuffix(s, suffix string) bool

HasSuffix tests whether the string s ends with suffix.

Code:play 

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 Uses

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.

Code:play 

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

Output:

4
-1

func IndexAny Uses

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.

Code:play 

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

Output:

2
-1

func IndexByte Uses

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.

func IndexFunc Uses

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.

Code:play 

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 Uses

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.

Code:play 

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

Output:

4
-1

func Join Uses

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.

Code:play 

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

Output:

foo, bar, baz

func LastIndex Uses

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.

Code:play 

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 Uses

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 LastIndexByte Uses

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.

func LastIndexFunc Uses

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 Uses

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.

Code:play 

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 Uses

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.

Code:play 

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

Output:

banana

func Replace Uses

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.

Code:play 

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 Uses

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.

Code:play 

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 Uses

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.

Code:play 

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

Output:

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

func SplitAfterN Uses

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

Code:play 

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

Output:

["a," "b,c"]

func SplitN Uses

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

Code:play 

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 Uses

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.

Code:play 

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

Output:

Her Royal Highness

func ToLower Uses

func ToLower(s string) string

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

Code:play 

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

Output:

gopher

func ToLowerSpecial Uses

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.

func ToTitle Uses

func ToTitle(s string) string

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

Code:play 

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

Output:

LOUD NOISES
ХЛЕБ

func ToTitleSpecial Uses

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.

func ToUpper Uses

func ToUpper(s string) string

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

Code:play 

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

Output:

GOPHER

func ToUpperSpecial Uses

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.

func Trim Uses

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.

Code:play 

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

Output:

["Achtung! Achtung"]

func TrimFunc Uses

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 Uses

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 Uses

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 TrimPrefix Uses

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.

Code:play 

var s = "Goodbye,, world!"
s = strings.TrimPrefix(s, "Goodbye,")
s = strings.TrimPrefix(s, "Howdy,")
fmt.Print("Hello" + s)

Output:

Hello, world!

func TrimRight Uses

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 Uses

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 Uses

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.

Code:play 

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

Output:

a lone gopher

func TrimSuffix Uses

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.

Code:play 

var s = "Hello, goodbye, etc!"
s = strings.TrimSuffix(s, "goodbye, etc!")
s = strings.TrimSuffix(s, "planet")
fmt.Print(s, "world!")

Output:

Hello, world!

type Reader Uses

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 Uses

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 Uses

func (r *Reader) Len() int

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

func (*Reader) Read Uses

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

func (*Reader) ReadAt Uses

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

func (*Reader) ReadByte Uses

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

func (*Reader) ReadRune Uses

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

func (*Reader) Reset Uses

func (r *Reader) Reset(s string)

Reset resets the Reader to be reading from s.

func (*Reader) Seek Uses

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

Seek implements the io.Seeker interface.

func (*Reader) Size Uses

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 Uses

func (r *Reader) UnreadByte() error

func (*Reader) UnreadRune Uses

func (r *Reader) UnreadRune() error

func (*Reader) WriteTo Uses

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

WriteTo implements the io.WriterTo interface.

type Replacer Uses

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 Uses

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.

Code:play 

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 Uses

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

Replace returns a copy of s with all replacements performed.

func (*Replacer) WriteString Uses

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.

Package strings imports 4 packages (graph) and is imported by 103680 packages. Updated 2017-02-17. Refresh now. Tools for package owners.