Golang：为什么compress / gzip Read函数不能读取文件内容？

I made a text file, that I then compressed with gzip. I then run the following go program to read the contents of that compressed file.

package main

import (
    "compress/gzip"
    "fmt"
    "os"
)

func main() {
    handle, err := os.Open("zipfile.gz")
    if err != nil {
        fmt.Println("[ERROR] File Open:", err)
    }
    defer handle.Close()

    zipReader, err := gzip.NewReader(handle)
    if err != nil {
        fmt.Println("[ERROR] New gzip reader:", err)
    }
    defer zipReader.Close()

    var fileContents []byte
    bytesRead, err := zipReader.Read(fileContents)
    if err != nil {
        fmt.Println("[ERROR] Reading gzip file:", err)
    }
    fmt.Println("[INFO] Number of bytes read from the file:", bytesRead)
    fmt.Printf("[INFO] Uncompressed contents: '%s'
", fileContents)
}

The response that I get is the following:

$ go run zipRead.go
[INFO] Number of bytes read from the file: 0
[INFO] Uncompressed contents: ''

Why am I not getting any contents from the file?

I have created zip files on both OS X and Ubuntu. I have build this go program on both OS X and Ubuntu with the same result.

io.Reader.Read will only read up to len(b) bytes. Since your fileContents is nil, its length is 0. Allocate some space for it to read into:

fileContents := make([]byte, 1024) // Read by 1 KiB.
bytesRead, err := zipReader.Read(fileContents)
if err != nil {
    fmt.Println("[ERROR] Reading gzip file:", err)
}
fileContents = fileContents[:bytesRead]

If you want to read the whole file, you'll have to either use Read several times, or use things like ioutil.ReadAll (which may be bad for big files).