DownloadObject.go

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

// snippet-start:[s3.go.download_object]
package main

// snippet-start:[s3.go.download_object.imports]
import (
	"flag"
	"fmt"
	"os"

	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/aws/aws-sdk-go/service/s3/s3manager"
)

// snippet-end:[s3.go.download_object.imports]

// DownloadObject downloads a file from a bucket
// Inputs:
//
//	sess is the current session, which provides configuration for the SDK's service clients
//	filename is the name of the file
//	bucket is the name of the bucket
//
// Output:
//
//	If success, nil
//	Otherwise, an error from the call to Create or Download
func DownloadObject(sess *session.Session, filename *string, bucket *string) error {
	// snippet-start:[s3.go.download_object.create]
	file, err := os.Create(*filename)
	// snippet-end:[s3.go.download_object.create]
	if err != nil {
		return err
	}

	defer file.Close()

	// snippet-start:[s3.go.download_object.call]
	downloader := s3manager.NewDownloader(sess)

	_, err = downloader.Download(file,
		&s3.GetObjectInput{
			Bucket: bucket,
			Key:    filename,
		})
	// snippet-end:[s3.go.download_object.call]
	if err != nil {
		return err
	}

	return nil
}

func main() {
	// snippet-start:[s3.go.download_object.args]
	bucket := flag.String("b", "", "The bucket to download from")
	filename := flag.String("f", "", "The name of the file to download")
	flag.Parse()

	if *bucket == "" || *filename == "" {
		fmt.Println("You must specify a bucket name (-b BUCKET) and filename (-f FILENAME")
		return
	}
	// snippet-end:[s3.go.download_object.args]

	// snippet-start:[s3.go.download_object.session]
	sess := session.Must(session.NewSessionWithOptions(session.Options{
		SharedConfigState: session.SharedConfigEnable,
	}))
	// snippet-end:[s3.go.download_object.session]

	err := DownloadObject(sess, filename, bucket)
	if err != nil {
		fmt.Println("Got error downloading " + *filename + ":")
		fmt.Println(err)
		return
	}

	fmt.Println("Downloaded " + *filename)
}

// snippet-end:[s3.go.download_object]