If you find yourself using a named profile for every awscli command, you can set it temporarily.
Listing a bucket with a named profile.
aws s3 ls --profile=yourprofile |
If you set AWS_PROFILE, you can then list a bucket without a named profile.
export AWS_PROFILE=yourprofile aws s3 ls |
After you are done, you can reset it back to default.
export AWS_PROFILE=default |