recompress.go

package main

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

func compress(name string, level int) error {
	// 由于压缩率影响，需要重新压缩文件
	f, err := os.OpenFile(name, os.O_RDONLY, 0644)
	if err != nil {
		return err
	}
	defer f.Close()

	zr, err := gzip.NewReader(f)
	if err != nil {
		return err
	}
	defer zr.Close()

	tmpf, err := os.OpenFile(fmt.Sprintf("%s.tmp", name), os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return err
	}
	defer f.Close()

	zw, err := gzip.NewWriterLevel(tmpf, level)
	if err != nil {
		return err
	}
	defer zw.Close()

	if _, err := io.Copy(zw, zr); err != nil {
		return err
	}

	// os.Rename(tmpf.Name(), f.Name())
	fmt.Println("rename to success", tmpf.Name())
	return nil
}

func main() {
	var (
		filename string
		level    int
	)

	flag.StringVar(&filename, "f", "", "special file")
	flag.IntVar(&level, "l", 5, "compress level")
	flag.Parse()
	if filename != "" {
		if err := compress(filename, level); err != nil {
			fmt.Println(err.Error())
		}
	}
}