Truncate

To truncate the content of a file under a certain dimension, and leave the file untouched if it's smaller, there is the os.Truncate method. Its usage is pretty simple, as shown in the following code:

package main

import "os"

func main() {
    // let's keep thing under 4kB
    if err := os.Truncate("file.txt", 4096); err != nil {
        fmt.Println("Error:", err)
    }
}