获取写入文件的字节的偏移量/位置

Question

I'm writing a string to a file, and I'd like to get the offset of the string which was just written. Here is the code writing the file:

package main

import (
    "os"
)

func main() {
    path := "test_file.txt"
    byteString := []byte("string to write")

    f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0600)
    if err != nil {
        panic(err)
    }

    defer f.Close()

    if _, err = f.Write(byteString); err != nil {
        panic(err)
    }
}

How can I get the offset after having written the line ?

Answer 1

os.Write only returns the length of the bytes written. If you want the offset, you can either:

1. Call os.Stat before writing, and then use os.WriteAt to write at the offset for the end of the file provided by the FileInfo structure.
2. Call os.Stat after writing, and subtract the length written to the file from the new size.