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Go join string

last modified April 11, 2024

In this article we show how to join strings in Golang.

To join strings, we can use the + operator, fmt.Sprintf function, and strings.Join function. 

$ go version
go version go1.22.2 linux/amd64

We use Go version 1.22.2.

Go join strings with + operator

Many programming languages use the + operator to join strings.

main.go
package main

import "fmt"

func main() {

    w1 := "old"
    w2 := "falcon"

    msg := w1 + " " + w2

    fmt.Println(msg)
}

Two words are joined in the example. We also add a space character between them. 

$ go run main.go 
old falcon

Go join strings with fmt.Sprintf

The fmt.Sprintf function builds a string according to the given format specifiers and returns the resulting string.

main.go
package main

import "fmt"

func main() {

    w1 := "old"
    w2 := "falcon"

    msg := fmt.Sprintf("%s %s", w1, w2)

    fmt.Println(msg)
}

The example builds a message by joining two words.

Go join strings with bytes.Buffer

A bytes.Buffer is a variable-sized buffer of bytes with Read and Write methods.

main.go
package main

import (
    "bytes"
    "fmt"
)

func main() {

    var buf bytes.Buffer

    buf.WriteString("an ")
    buf.WriteString("old ")
    buf.WriteString("falcon")

    fmt.Println(buf.String())
}

In the example, we write strings to the bytes buffer with WriteString and then convert the bytes into a final string with String function. 

$ go run main.go 
an old falcon

Go strings.Join

The strings.Join function joins string elements of a slice/array into one string. The separator string is placed between elements in the resulting string.

fmt_funs.go
package main

import (
    "fmt"
    "strings"
)

func main() {

    words := []string{"an", "old", "falcon"}
    msg := strings.Join(words, " ")

    fmt.Println(msg)
}

We have a slice of words. We join them with strings.Join, utilizing a single space as a separator.

Go String function

The String function of an object is called when it is passed to any of the print functions. It is commonly used to display a human-readable representation of the object.

main.go
package main

import (
    "fmt"
)

type User struct {
    Name       string
    Occupation string
}

func (u User) String() string {

    return fmt.Sprintf("%s is a(n) %s", u.Name, u.Occupation)
}

func main() {

    u1 := User{"John Doe", "gardener"}
    u2 := User{"Roger Roe", "driver"}

    fmt.Println(u1)
    fmt.Println(u2)
}

In the example, we use the fmt.Sprintf function to generate an output of a User type. 

$ go run main.go 
John Doe is a(n) gardener
Roger Roe is a(n) driver

Source

The Go Programming Language Specification

In this article we have showed how to join strings in Golang.

Author

My name is Jan Bodnar and I am a passionate programmer with many years of programming experience. I have been writing programming articles since 2007. So far, I have written over 1400 articles and 8 e-books. I have over eight years of experience in teaching programming.

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