Docker MongoDB: mongodump backup

This is a script to run mongodump in a running MongoDB container, and backup to the local server as a tgz file.
1.) Runs mongodump
2.) Creates a tgz file where the script is ran
3.) Removes any old tgz files that are in the same directory

// My MongoDB is container is running in Docker Swarm mode to use Docker Secrets.

#!/bin/bash

set -euo pipefail

# Create a temp directory for the backup
TMPDIR="$(mktemp -d)"
trap "rm -rf $TMPDIR" EXIT

# Get the running MongoDB container ID
CONTAINER_ID=$(docker ps --filter "name=btc_mongodb" --format "{{.ID}}" | head -n 1)
if [ -z "$CONTAINER_ID" ]; then
  echo "No running container found with 'btc_mongodb' in its name."
  exit 1
fi

# Retrieve MongoDB credentials from secrets in the container
USERNAME=$(docker exec "$CONTAINER_ID" cat /run/secrets/mongo_root_username)
PASSWORD=$(docker exec "$CONTAINER_ID" cat /run/secrets/mongo_root_password)

# Run mongodump inside the container, outputting to /tmp
docker exec "$CONTAINER_ID" mongodump \
  --uri="mongodb://$USERNAME:$PASSWORD@localhost:27017/" \
  --out /tmp/mongodump

# Copy the mongodump from the container to the host's temp directory
docker cp "$CONTAINER_ID":/tmp/mongodump "$TMPDIR"

# Create the archive in the current directory
BACKUP_FILENAME="$(date +%Y-%m%d-%H%M)-btcMongo.tgz"
tar -czf "$BACKUP_FILENAME" -C "$TMPDIR/mongodump" .

# Remove any previous *-btcMongo.tgz except the newly created one
for f in *-btcMongo.tgz; do
  if [[ "$f" != "$BACKUP_FILENAME" ]]; then
    rm -f -- "$f"
  fi
done

echo "Backup complete: $BACKUP_FILENAME"