Quickly list sizes of AWS S3 buckets without traversing all objects.

ls-s3-sizes.sh

#!/bin/bash
# Justin Miller 12/01/17
# Script to calculate the human readable size of S3 buckets
# The script uses cloudwatch metrics.  These may need time to update if you've added data to a bucket within 24hrs.
# It happily DOES NOT need to travese potentially millions of files to calculate your S3 bucket sizes.
#
# Usage:
#       ./ls-s3-sizes.sh
#
# TODO: Could be further parameterised depending on usage requirements.

PROFILE="default" # update to relect the Credentials profile you'd like to use, typicaly in ~/.aws/credentials
REGION="eu-west-1" # specify a region
STORAGE_CLASS="StandardIAStorage" # a storage class is required.  Either "StandardStorage" or "StandardIAStorage" for infrequent access
SHOW_ZERO_SIZE_BUCKETS="false"

# Check if jq is available
type jq >/dev/null 2>&1 || { echo >&2 "The jq utility is required for this script to run."; exit 1; }

# Check if aws cli is available
type aws >/dev/null 2>&1 || { echo >&2 "The aws cli is required for this script to run."; exit 1; }

BUCKETS=$(aws --profile $PROFILE s3 ls | cut -d' ' -f3)

function BucketSize () {
        BUCKET=$1
        NOW=$(date +%s)
        BUCKET_SIZE_BYTES=$(aws --profile $PROFILE cloudwatch \
                                get-metric-statistics \
                                --namespace AWS/S3 \
                                --start-time "$(echo "$NOW - 86400" | bc)" \
                                --end-time "$NOW" \
                                --period 86400 \
                                --statistics Average \
                                --region $REGION \
                                --metric-name BucketSizeBytes \
                                --dimensions \
                                Name=BucketName,Value="$BUCKET" \
                                Name=StorageType,Value=$STORAGE_CLASS | jq '.Datapoints[].Average')

        if [[ $BUCKET_SIZE_BYTES > 1 ]]; then
                BUCKET_SIZE_GB=$(echo "scale=2; $BUCKET_SIZE_BYTES/1073741824" | bc -l)
                echo -e "${BUCKET_SIZE_GB}GB - $BUCKET"
        else
                BUCKET_SIZE_GB=0
                if [ $SHOW_ZERO_SIZE_BUCKETS == "true" ]; then
                        echo -e "${BUCKET_SIZE_GB}GB - $BUCKET"
                fi
        fi
}

TOTAL_SIZE=0
for MYBUCKET in ${BUCKETS[*]}; do
        BucketSize "$MYBUCKET"
        TOTAL_SIZE=$(echo "scale=2; $TOTAL_SIZE+$BUCKET_SIZE_GB" | bc -l)
done

echo "${TOTAL_SIZE}GB - GRAND TOTAL"

didn't work for me.