Two different approaches to debugging a software problem:

The Sudoku approach: stare at the limited set of clues you have, and think harder and harder about them until you find a way to deduce something useful.

The Minesweeper approach: don't even try to figure out the solution from only the clues you have right now. Instead, focus on finding a way to acquire another clue, and then using that to get another, and so on. Eventually you've collected so many clues that the answer is obvious.

Sometimes the Sudoku approach is necessary, because you've got all the clues you're ever going to get. But I think my new motto is "Never Sudoku a problem when you can Minesweeper it."

I was today years old when I learned that, in #Wireshark, you can define columns that source their values from multiple fields, for example:

tcp.dstport || udp.dstport

Suppose you're using less(1) to view a config file that has lots of commented-out explanations and defaults:

less /etc/ssh/ssh_config

It's hard to really see which lines are in effect and which are just comments, especially without syntax highlighting.

But! You can use less's filtering capabilities to only display lines that start with a character that's not a hash symbol. Type "&" and enter a regular expression, then hit return. For example:

&^[^#]

Enter an empty regex to stop filtering.