You can use the -L option to generate a manifest file of all files that were copied. From the documentation:
-L <file> Outputs a manifest log file with detailed information about each item that was copied. This manifest contains the following information for each item:
- Source path.
- Destination path.
- Source size.
- Bytes transferred.
- MD5 hash.
- UTC date and time transfer was started in ISO 8601 format.
- UTC date and time transfer was completed in ISO 8601 format.
- Upload id, if a resumable upload was performed.
- Final result of the attempted upload, success or failure.
- Failure details, if any.
A specific example:
$ echo "hey" | gsutil cp -L manifest.txt - gs://mybucket/hey.txt
Copying from <STDIN> [Content-Type=application/octet-stream]...
$ cat manifest.txt
Source,Destination,Start,End,Md5,UploadId,Source Size,Bytes Transferred,Result,Description
file://-,gs://mybucket/hey.txt,2013-05-29T21:29:31.847715Z,2013-05-29T21:29:32.115624Z,081ecc5e6dd6ba0d150fc4bc0e62ec50,,,0,OK,