--etag-compare

Make a conditional HTTP request for the specific ETag read from the given file by sending a custom If-None-Match header using the stored ETag.

For correct results, make sure that the specified file contains only a single line with the desired ETag. A non-existing or empty file is treated as an empty ETag.

Use the option --etag-save to first save the ETag from a response, and then use this option to compare against the saved ETag in a subsequent request.

Use this option with a single URL only.