Is there an Go function for truncating string?

Question

Please help me write a function that takes input of a string and a number and outputs a shortened string to the number + "...". If the string does not exceed the size (number), then just output this string, but without the "...". Also, our string uses only single-byte characters and the number is strictly greater than zero.

My two attempts:

package main

import (
        "fmt"
)
func main() {
var text string
var width int
fmt.Scanf("%s %d",&text,&width)
res := text[:width]
fmt.Println(res+"...")
}

But this function adds "..." even if the string does not exceed the width.

package main
import (
        "fmt"
)
var text string
var width int
fmt.Scanf("%s %d",&text,&width)
if width <= 0 {
    fmt.Println("")
}
res := ""
count := 0
for _, char := range text {
res += string(char)
    count++
    if count >= width {
        break
    }
}
fmt.Println(res+"...")
}

This function works the same way.

The easiest would be to convert the string to `[]rune`, so you can check how many runes it has. Only slice it and append `...` if it's greater than the limit. — icza, Oct 11 '21 at 14:37
dup with good answers https://stackoverflow.com/questions/46415894/golang-truncate-strings-with-special-characters-without-corrupting-data — , Oct 16 '21 at 09:36

score 1 · Answer 1 · answered Oct 13 '21 at 03:42

To continue with what @Marcelloh said

Here's an example of using runes instead of bytes.

package main

import (
    "fmt"
)

func Truncate(text string, width int) (string, error) {
    if width < 0 {
        return "", fmt.Errorf("invalid width size")
    }
    
    r := []rune(text)
    trunc := r[:width]
    return string(trunc)+ "...", nil
}

func main() {
    word, err := Truncate("Hello, World", 3)
    if err != nil {
        fmt.Println(err.Error())
    }
    fmt.Println(word)
    // Output: Hel...
}

mb chars version https://play.golang.org/p/BGRXm3sM4_g – Oct 16 '21 at 09:25 — , Oct 16 '21 at 09:25

score 0 · Answer 2 · answered Oct 11 '21 at 15:34

0

Just a basic example that can get you going :-)

func main() {
    var text string
    var width int = 12
    text = "a ver long string of text to be shortened"
    if len(text) > width {
        text = string([]byte(text)[:width])

    }
    fmt.Println(text + "...")
}

Of course, you need to read about runes, and some "strings" have a length of 3, while you see only one. But for normal ASCII, the above would do the trick.

answered Oct 11 '21 at 15:34

Marcelloh

82
1
5

I have plussed, but please add a comment about the matters about why runes, bytes etc https://play.golang.org/p/ayMp_gpRrag – Oct 16 '21 at 09:23
Look at this to understand why runes are a bit different in their length: https://goplay.space/#fSmFO6SLIDQ – Marcelloh Oct 18 '21 at 06:34

score -1 · Answer 3 · edited Oct 16 '21 at 08:24

-1

package main

import (
    "fmt"
)

func main(){
    var text string
    var width int
    fmt.Scanf("%s %d",&text,&width)
    res := []rune(text)
    if len(res) > width {
        res = res[:width]
        fmt.Println(string(res)+"...")
    } else {
        fmt.Println(string(res))
    }
}

edited Oct 16 '21 at 08:24

Ryan M

18,333
31
67
74

answered Oct 15 '21 at 13:09

Илья Калошин

3
1
2

Is there an Go function for truncating string?

3 Answers3