You can use 10 GiB of Object Storage and 10 GiB of Archive Storage for free in your home region.
To delete all files from a bucket...
oci os object bulk-delete -bn mybucket
Pre-authenticated requests provide a way to let users access a bucket or an object without having their own credentials. When you create a pre-authenticated request, a unique URL is generated. Users in your organization, partners, or third parties can use this URL to access the targets identified in the pre-authenticated request. (1)
To show the pre-authenticated requests for a bucket...
oci os preauth-request list -bn mybucket
oci os preauth-request create --namespace mynamespace --bucket-name mybucket --name myPAR --access-type AnyObjectReadWrite --time-expires="2022-11-21T23:00:00+00:00" --bucket-listing-action ListObjects
This will return an access-uri (amongst other things). You should make a note of this URI as it's not possible to retrieve it again later.
To delete all pre-authenticated requests for a bucket...
for idz in `oci os preauth-request list -bn mybucket |\
grep id | awk '{print $2}' | sed 's/",//g' | sed 's/"//g'`; \
do echo y | \
oci os preauth-request delete -bn mybucket --par-id $idz ; \
done