I already wrote about bash 'history'. Also neat is "some really long command >& file.out &" followed by "tail -f file.out". You can watch the output of your long process as it scrolls by and still save a copy to disk. Nift.
I recently discovered that <math.h> #define's the symbol DOMAIN to be 1. If you have code that, say, has an enumerated type that includes the also refers to the constant DOMAIN (eg, the domain of a web page), and also include math.h, then the compiler will give some cryptic message about not expecting to find a "1" in the enumeration list.
When I was gearing up to head home this evening, I discovered that my bike chain and sprokets are devoid of grease and the chain has some slight rust. D'oh! I thought things on my bike sounded creaky during the last day or three. I put some spray teflon lubricant (Tri-Flow) on it this evening which should hold me over through tomorrow. But I need to regrease my chain before I put many more miles on it. Like, 10 more miles would be a bad idea.
I discovered that, unbeknownst to me, my body's been building up its winter's supply of fat cells. Silly body - I live in California. What do I need fat cells for? I don't mind gaining weight -- I just want some say as to where it will end up.
I discovered that I really can grok naive Bayes probabilities. I added some debugging output to a program I'm writing at work to split out what P(hypothesis | observations) should be for various values of observations. And, it makes sense. That was neat.
I discovered that both my cube-mates live about 1.5 miles from my apartment. And I discovered that one of them likes to play tennis. We have a tentative tennis plan for early next month.
Finally, I discovered that what makes me happiest is making other people happy. Heh, I already knew this, but I had to match the parallel structure of my entry. Several people have said complementary things about my Christmas decorations at work, along the lines of "it makes me smile whenever I see it." Hard not to feel good inside from comments like that.