Filter S3 list-objects results to find a key matching a pattern

Question

I would like to use the AWS CLI to query the contents of a bucket and see if a particular file exists, but the bucket contains thousands of files. How can I filter the results to only show key names that match a pattern? For example:

aws s3api list-objects --bucket myBucketName --query "Contents[?Key==*mySearchPattern*]"

Solution

The --query argument uses JMESPath expressions. JMESPath has an internal function contains that allows you to search for a string pattern.

This should give the desired results:

aws s3api list-objects --bucket myBucketName --query "Contents[?contains(Key, `mySearchPattern`)]"

(With Linux I needed to use single quotes ' rather than back ticks ` around mySearchPattern.)

If you want to search for keys starting with certain characters, you can also use the --prefix argument:

aws s3api list-objects --bucket myBucketName --prefix "myPrefixToSearchFor"