Golang : Gzip file example
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
See also : Golang : Gunzip file
By Adam Ng
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