Golang : Gzip file example



Tags : golang gzip gz

This tutorial is to fulfill a request from a student learning Golang in Senegal.

His question is how to gzip a file in Golang. Most of the online articles he found only show how to compress some bytes of text but not how to compress a file. This tutorial will show how to read an uncompress file content into a buffer, gzip the buffer and write out the buffer content into a new file.

Here we go :

 package main

 import (
 "bufio"
 "bytes"
 "compress/gzip"
 "flag"
 "fmt"
 "io/ioutil"
 "os"
 )

 func main() {

 flag.Parse() // get the arguments from command line

 filename := flag.Arg(0)

 if filename == "" {
 fmt.Println("Usage : go-gzip sourcefile")
 os.Exit(1)
 }

 rawfile, err := os.Open(filename)

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }
 defer rawfile.Close()

 // calculate the buffer size for rawfile
 info, _ := rawfile.Stat()

 var size int64 = info.Size()
 rawbytes := make([]byte, size)

 // read rawfile content into buffer
 buffer := bufio.NewReader(rawfile)
 _, err = buffer.Read(rawbytes)

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 var buf bytes.Buffer
 writer := gzip.NewWriter(&buf)
 writer.Write(rawbytes)
 writer.Close()

 err = ioutil.WriteFile(filename+".gz", buf.Bytes(), info.Mode())
 // use 0666 to replace info.Mode() if you prefer

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 fmt.Printf("%s compressed to %s\n", filename, filename + ".gz")

 }

Sample tests result :

./go-gzip

Usage : go-gzip sourcefile

./go-gzip uncompressed.txt

uncompressed.txt compressed to uncompressed.txt.gz

References :

http://golang.org/pkg/compress/gzip/#NewWriter

https://www.socketloop.com/tutorials/golang-read-binary-file-into-memory

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  See also : Golang : Gunzip file



Tags : golang gzip gz

By Adam Ng

IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.


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