Using AWS CLI
aws s3 ls s3://mybucket/ --recursive | wc -l
or
aws cloudwatch get-metric-statistics
--namespace AWS/S3 --metric-name NumberOfObjects
--dimensions Name=BucketName,Value=BUCKETNAME
Name=StorageType,Value=AllStorageTypes
--start-time 2016-11-05T00:00 --end-time 2016-11-05T00:10
--period 60 --statistic Average
Note: The above cloudwatch command seems to work for some while not for others. Discussed here: https://forums.aws.amazon.com/thread.jspa?threadID=217050
Using AWS Web Console
You can look at cloudwatch's metric section to get approx number of objects stored.
I have approx 50 Million products and it took more than an hour to count using aws s3 ls
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…