从文件获取倒数第二行

Question

I found a method how to read last line in file, but last line in my file is empty, I need to read the next-to-last line and I have no idea how to do it, please help a bit.

func ll(z string) string {

    f, err := os.Open(z)
    if err != nil {
        log.Fatal(err)
    }
    bf := bufio.NewReader(f)
    for {
        switch line, err := bf.ReadString('
'); err {
        case nil:
        // valid line, echo it.  note that line contains trailing 
.
        fmt.Println(line)

        case io.EOF:
            if line > "" {
                // last line of file missing 
, but still valid
                    fmt.Println(line, "in func")
            }
            return  line
        default:
            log.Fatal(err)
        }
    }
}

Answer 1

Just save the current line every iteration, so that when you encounter the last one, you can return prev_line:

func next_to_last(z string) string {
    f, err := os.Open(z)
    if err != nil {
        log.Fatal(err)
    }
    bf := bufio.NewReader(f)
    prev_line := ""

    for {
        switch line, err := bf.ReadString('
'); err {

        case nil:
        // valid line, echo it.  note that line contains trailing 
.
        fmt.Println(line)
        prev_line = line // Save line as previous

        case io.EOF:
            if line > "" {
                // last line of file missing 
, but still valid
                    fmt.Println(line, "in func")
            }
            return  prev_line // Return previous line

        default:
            log.Fatal(err)
        }
    }
}