Macros are for more than just canned searches.

If you've never seen a macro before, read the doc page here:

https://docs.splunk.com/Documentation/Splunk/9.0.2/Knowledge/Definesearchmacros

What that doc page doesn't tell you is that you need not just stick any old complicated search in there. If you know how to use eval you can stick any resulting text anywhere you want.

Take for example, timestamping your output lookups. Let's say I have a report that runs every 12 hours that I output to a lookup called "vpn_users.csv," which contains all users who logged on to VPN in that time. That report might look something like this:

index=syslog sourcetype=vpn
    | table _time username 
    | outputlookup vpn_users.csv

I can easily review that lookup like so:

| inputlookup vpn_users.csv

My boss might be happy that I'm keeping an eye on things, but what's the historical picture? How do I know what's a red flag and what isn't?

What I might do is combine all of the days' reports into one each day, and then compare each one to today's. But in the original report logic, this gets overwritten every 12 hours. You could just append forever, but then you're not looking at just twelve hours, unless you add a time constraint to your search. How do I get to a daily report without interrupting the reports already running?

One way to do it is to create a second combined report unique to that day, for example 'vpn_users-2022_11_17.csv'. The way you insert that text is with a macro, defined for the current date. For this particular format, I can define a macro called today with the following definition, which just gets the current time and formats it:

strftime(now(), "%Y-%m-%d")

Now I literally just stick it to the end of my original search, and set the lookup file to append, so we add new values rather than overwrite them:

index=syslog sourcetype=vpn
    | table _time username 
    | outputlookup vpn_users.csv
    | outputlookup append=t vpn_users-`today`.csv

That's just a super obvious implementation though; there's all sorts of ways you might want to tag your lookups for ease of access.