How to print the bytes while the file is being downloaded ? -golang

Question

I\'m wondering if it\'s possible to count and print the number of bytes downloaded while the file is being downloaded.

out, err := os.Create(\"file.txt\")
    d         


        

Answer 1

The stdlib now provides something like jimt's PassThru: io.TeeReader. It helps simplify things a bit:

// WriteCounter counts the number of bytes written to it.
type WriteCounter struct {
    Total int64 // Total # of bytes transferred
}

// Write implements the io.Writer interface.  
// 
// Always completes and never returns an error.
func (wc *WriteCounter) Write(p []byte) (int, error) {
    n := len(p)
    wc.Total += int64(n)
    fmt.Printf("Read %d bytes for a total of %d\n", n, wc.Total)
    return n, nil
}

func main() {

    // ...    

    // Wrap it with our custom io.Reader.
    src = io.TeeReader(src, &WriteCounter{})

    // ...
}

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