Can I set up a cron job to run every 15 minutes throughout the day, except for 3:00 AM? I have another task that I want to run at 3:00 AM and don't want these two conflicting.

Crontab evaluates each line independently. There's no way to say “every 15 minutes except these” in a single line — the minute field accepts a list (0,15,30,45), a step (*/15), and ranges, but it has no negation operator.

The pattern in the answer is the canonical workaround: split the day into two ranges of hours (0-2 and 4-23) and exclude the hour you don't want via the hour field. The second cron line handles the surviving slots within the excluded hour (3:15, 3:30, 3:45 — everything except 3:00). The third cron line schedules the conflicting job at exactly 3:00, ensuring it has the slot to itself.

A more advanced approach uses a wrapper script that exits early when the current time matches the exclusion window — but that hides the schedule from crontab -l, which often hurts more than it helps. Stick with multi-line cron when you want the schedule to be self-documenting, and use the multi-cron visualizer to confirm there's no overlap.