Count S3 objects and total their size

Part 41 of AWS from Zero. This lesson keeps the scope to one S3 behavior you can verify from the terminal.

What we are learning

A query can turn an object listing into a quick inventory summary without a separate script.

Before you run it

aws sts get-caller-identity
REGION="ap-south-1"
BUCKET="replace-with-your-private-demo-bucket"

Use a private general purpose bucket that you own. Replace every placeholder before running a write or delete command.

The command

aws s3api list-objects-v2 \
  --bucket "$BUCKET" \
  --query "{ObjectCount:length(Contents),TotalBytes:sum(Contents[].Size)}"

A successful configuration command may return no output. Treat inspection as a separate required step.

Inspect the result

aws s3api list-objects-v2 \
  --bucket "$BUCKET" \
  --prefix "reports/" \
  --query "{ObjectCount:length(Contents),TotalBytes:sum(Contents[].Size)}" \
  --output table

The count and sum apply to the objects returned by the command after prefix and pagination behavior.

One tiny variation

aws s3 ls "s3://$BUCKET/" --recursive --summarize

The high-level command prints a human-oriented total. The API query is easier to compose into scripts.

Common mistake

For very large buckets, a live listing is not a cheap analytics system. S3 Inventory is usually better for repeated full-bucket reporting.

Cleanup

# This lesson does not require an additional persistent resource.
aws s3api head-bucket --bucket "$BUCKET"

Keep the shared demo bucket for the next lesson, or remove only the configuration and objects created here.

Next, we will learn Upload an S3 object with a SHA-256 checksum.

Official AWS CLI reference