s3-cat is a simple command line utility that lets you search many S3 files quickly.
gem install s3_cat$ s3-cat s3://my_s3_bucket/directory/path/ | grep "searched pattern"
s3-cat prints content of all the files within directory/path/ to standard output.
It can be later processed with any other tool.
The gem is available as open source under the terms of the MIT License.