list s3 directory by depth

main.go

// usage:
// $ AWS_PROFILE=foo AWS_REGION=us-east-1 go run . example-bucket 3
package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"strconv"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/service/s3"
)

type S3Lister interface {
	ListObjectsV2(ctx context.Context, params *s3.ListObjectsV2Input, optFns ...func(*s3.Options)) (*s3.ListObjectsV2Output, error)
}

func main() {

	// args
	args := os.Args[1:]
	if len(args) != 2 {
		fmt.Println("must give 2 args: BucketName and Depth")
		os.Exit(1)
	}

	Bucket := args[0]
	Depth, err := strconv.Atoi(args[1])
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	ctx := context.TODO()

	// Load the Shared AWS Configuration (~/.aws/config)
	cfg, err := config.LoadDefaultConfig(ctx)
	if err != nil {
		log.Fatal(err)
	}

	// begin
	if err := step(s3.NewFromConfig(cfg), ctx, Bucket, nil, uint(Depth), func(object string) {
		fmt.Println(object)
	}); err != nil {
		log.Fatal(err)
	}
}

func step(
	client S3Lister,
	ctx context.Context,
	Bucket string,
	Prefix *string,
	depth uint,
	fn func(p string),
) error {

	// emit if at desired depth
	if depth == 0 {
		fn(*Prefix)
		return nil
	}

	// list
	output, err := client.ListObjectsV2(ctx, &s3.ListObjectsV2Input{
		Bucket:    &Bucket,
		Prefix:    Prefix,
		Delimiter: aws.String("/"),
	})
	if err != nil {
		return err
	}

	// recurse
	for _, CommonPrefix := range output.CommonPrefixes {
		if err := step(client, ctx, Bucket, CommonPrefix.Prefix, depth-1, fn); err != nil {
			return err
		}
	}

	return nil
}

ever wanted to ls an s3 bucket with a directory depth? Now you can!

Known issues:

• paginate if more than 1000 items exist within a delimiter prefix
• mix of log.Fatal and fmt.Print + os.Exit (pick one)