Golang : Compress and decompress file with compress/flate example

A quick and simple tutorial on how to compress a file with Golang's compress/flate package. Package flate implements the DEFLATE compressed data format, as described in RFC 1951.

To compress a file, pipe and flush the data out with NewWriter() function :

 package main

 import (
 "compress/flate"
 "fmt"
 "io"
 "os"
 )

 func main() {
 inputFile, err := os.Open("file.txt")

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

 defer inputFile.Close()

 outputFile, err := os.Create("file.txt.compressed")

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

 defer outputFile.Close()

 flateWriter, err := flate.NewWriter(outputFile, flate.BestCompression)

 if err != nil {
 fmt.Println("NewWriter error ", err)
 os.Exit(1)
 }

 defer flateWriter.Close()
 io.Copy(flateWriter, inputFile)

 flateWriter.Flush()
 }

Sample test data :

>cat file.txt

This is a test file for Golang Compress/Flate

This is a test file for Golang Compress/Flate

This is a test file for Golang Compress/Flate

This is a test file for Golang Compress/Flate

This is a test file for Golang Compress/Flate

This is a test file for Golang Compress/Flate

>cat file.txt.compressed

��,V�D������T���"��ļt��܂���b}��ĒT�Q�#U5����

To decompress the file, read in the compressed data with NewReader() function before piping out the decompressed data to file

 package main

 import (
 "compress/flate"
 "fmt"
 "io"
 "os"
 )

 func main() {
 inputFile, err := os.Open("file.txt.compressed")

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

 defer inputFile.Close()

 outputFile, err := os.Create("file.txt.decompressed")

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

 defer outputFile.Close()

 flateReader := flate.NewReader(inputFile)

 defer flateReader.Close()
 io.Copy(outputFile, flateReader)

 }

Happy coding!

Reference :

https://golang.org/pkg/compress/flate/