You cannot directly but you can extend your search by adding this to the end of it to recreate the log file:
| map [index=YourIndexHere source=$source$]
If your original search returns nothing, then so will this extension, but if it returns anything then it will reconstruct the entire file for each result.
You will alert email with attachment based on your query output. That is your source right. You want attach external file along with the alert.
If you want result to be attached while alerting below is the link,
Okay, since that would be a file of an unknown size, it's probably not what you really want.
Probably, what you really want is for your alert to kick off a report that will extract certain kinds of records for a certain number of seconds or minutes from the log file and mail that to you.
So, YES, splunk can do that.