🪓 8 ways to split a string in Go

String splitting is one of the most common actions in everyday programming. Often, one single string has to be split into a list of substrings according to a specific separator, such as when parsing user-entered arguments, environment variables, or column data from a CSV file row. In Go, there are many different ways to split strings. We found 8 of them in the standard packages, so you have a wide range of tools you can use to perform this task.

Split a string by separator

To split a string in Go, use the strings.Split() function from the strings package. It splits a string into a list of substrings using the specified delimiter. The output substrings do not contain the separator.

The function signature is

• s is the string to split
• sep is a separator (delimiter) by which the string is split

Example

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "strawberry, blueberry, raspberry"
    fmt.Printf("strings.Split(): %#v\n", strings.Split(str, ", "))
}

Output:

strings.Split(): []string{"strawberry", "blueberry", "raspberry"}

Split a string without removing the separator

To split a string in Go into substrings containing the separator by which they were split, use the strings.SplitAfter() function. It splits a string after each occurrence of the delimiter.

The functions signature:

• s is the string to split
• sep is a separator (delimiter) by which the string is split

Example

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "strawberry, blueberry, raspberry"
    fmt.Printf("strings.SplitAfter(): %#v\n", strings.SplitAfter(str, ", "))
}

Output:

strings.SplitAfter(): []string{"strawberry, ", "blueberry, ", "raspberry"}

Cut a string into 2 parts

To cut a string on the first occurrence of the delimiter in Go, use the strings.Cut() function. It slices a string and returns the text before and after the separator.

The function signature:

Example

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "strawberry, blueberry, raspberry"
    before, after, found := strings.Cut(str, ", ")
    fmt.Printf("strings.Cut():\nbefore: %s\nafter: %s\nseparator found: %t\n", before, after, found)
}

Output:

strings.Cut():
before: strawberry
after: blueberry, raspberry
separator found: true

Split a string to at most n substrings

To split a string in Go and receive at most n substrings, use the strings.SplitN() function. The last substring in this case will be the unsplit remainder.

The function signature:

The strings.SplitN() function works the same way as strings.Split() except that it finishes after n substrings.

Example

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "strawberry, blueberry, raspberry"
    fmt.Printf("strings.SplitN(): %#v\n", strings.SplitN(str, ", ", 2))
}

Output:

strings.SplitN(): []string{"strawberry", "blueberry, raspberry"}

Split a string without removing the separator to at most n substrings

To split a string in Go into output substrings containing a separator and getting at most n substrings, use the strings.SplitAfterN() function. It splits a string after each occurrence of the delimiter, and the last substring will be the unsplit remainder.

The function signature:

The strings.SplitAfterN() function works the same way as strings.SplitAfter() except that it finishes after n substrings.

Example

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "strawberry, blueberry, raspberry"
    fmt.Printf("strings.SplitAfterN(): %#v\n", strings.SplitAfterN(str, ", ", 2))
}

Output:

strings.SplitAfterN(): []string{"strawberry, ", "blueberry, raspberry"}

Split a string by white space characters

To split a string by white space characters in Go, use the strings.Fields() function. It takes a string as an argument and splits it according to the white space characters defined by the unicode.IsSpace() function.

The function signature:

Example

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "strawberry, blueberry, raspberry"
    fmt.Printf("strings.Fields(): %#v\n", strings.Fields(str))
}

Output:

strings.Fields(): []string{"strawberry,", "blueberry,", "raspberry"}

Split a string by a splitting function

To split a string according to a custom split function in Go, use the strings.FieldsFunc(). As arguments, it gets the string to split and the func(rune) bool function, which should return true if splitting should be done for a given rune.

The function signature:

Example

In the example, the string is split on runes that are not Unicode letters.

package main

import (
    "fmt"
    "strings"
    "unicode"
)

func main() {
    str := "strawberry, blueberry, raspberry"
    fmt.Printf("strings.FieldsFunc(): %#v\n", strings.FieldsFunc(str, func(r rune) bool {
        return !unicode.IsLetter(r)
    }))
}

strings.FieldsFunc(): []string{"strawberry", "blueberry", "raspberry"}

Split a string using the regexp

In Go, you can also split a string using a Regular Expression. To do this, you must first create a new regular expression object Regexp, for example, by calling the regexp.MustCompile() function. The Regexp object has the Split() method that splits a given string s by the regular expression into at most n substrings (the last substring will be the unsplit remainder).

The method signature:

Example

package main

import (
    "fmt"
    "regexp"
)

func main() {
    str := "strawberry,blueberry,    raspberry"

    regex := regexp.MustCompile(",\\s*")

    fmt.Printf("Regexp.Split(): %#v\n", regex.Split(str, -1))
}

Output:

Regexp.Split(): []string{"strawberry", "blueberry", "raspberry"}