SIGINT(2) vs SIGTERM(15)

This is another of those things that I've always known I should just sit down and learn but never did: what's the difference between SIGINT and SIGTERM? I knew that one of them corresponded to control-c, and the other corresponded to the kill command's default signal, but I always treated them the same, so I never learned which was which.

• SIGINT (2) - User interrupt signal, typically sent by typing control-C. The receiving program should stop performing its current operation and return as quickly as appropriate. For programs that maintain some kind of persistent state (e.g. data files), those programs should catch SIGINT and do enough cleanup to maintain consistency of state. For interactive programs, control-C might not exit the program, but instead return to the program's internal command prompt.
  
  
• SIGTERM (15) - Graceful termination signal. For example, when the OS gracefully shuts down, it will send SIGTERM to all processes. It's also the default signal sent by the "kill" command. It is not considered an emergency and so does not expect the fastest possible exit; rather a program might allow the current operation to complete before exiting, so long as it doesn't take "too long" (whatever that is). Interactive programs should typically NOT return to their internal command prompt and should instead clean up (if necessary) and exit.

This differentiation was developed when the Unix system had many users and a system operator. If the operator initiated a shutdown, the expectation was that interactive programs would NOT just return to the command prompt, but instead would respect the convention of cleaning up and exiting.

However, I've seen that convention not followed by "personal computer" Unix systems, like MacOS. With a personal computer, you have a single user who is also the operator. If you, the user and operator, initiate a shutdown on a Mac, there can be interactive programs that will pause the shutdown and ask the user whether to save their work. It still represents a difference in behavior between SIGINT and SIGTERM - SIGINT returns to normal operation while SIGTERM usually brings up a separate dialogue box warning the user of data loss - but the old expectation of always exiting is no longer universal.

Keychron K2 Keyboard

 I mentioned buying a Keychron K2 keyboard almost two years ago, but that post was primarily about a different vendor's keyboard which was a fail.

I just bought a second Keychron K2 keyboard ("blue" switches), but not because of a problem. It's because the keyboard is wonderful, and I want a second one to keep at an alternate worksite.

The laptop keyboard on the 2017-vintage Macbook Pro is almost unusable. Really, even the 2015-vintage Air's laptop keyboard is not that great. I prefer a full-stroke "clicky" keyboard with good tactile feedback.

Enter the Keychron K2. Lots of nice features that I won't bother listing since I don't use most of them and the site explains them fine. I like the noisy "blue" style switches, but you can get quieter ones.

Also, it has all the Mac-specific special keys, right there (I don't like the touch-bar at the top of the Macbooks.) And I also like the compact size.

My only complaint is that the key caps are not dual-injected, which means that the paint can wear off the tops of the frequently-used keys (E and A). But this is a problem for most keyboards I use; I apparently have a heavy typing hand.

Count me as a satisfied customer.

Matias keyboard FAIL

Like many Mac owners, I don't like the chiclet keyboards. I like an old-fashioned mechanical keyboard. So I finally got one: a very clicky Matias keyboard. And while I would have preferred a smaller keyboard (I don't need the keypad), I was very happy with it. For about a month.

Then the spacebar started "bouncing". I.e. maybe 1 time in 20 I get two spaces instead of one. I experimented quite a bit, and it's not the autorepeat, and it's not *me* that's bouncing. I can slowly press the key, and bam - two spaces. Or I can type my normal (pretty fast) speed and get periodic bounces. (Sometimes I can go an hour without a bounce, but then they come back.)

So I contacted Matias support, and after leading me through a series of unsuccessful steps, they sent me a new one. It arrived with NO BOUNCE! Happy-happy.

For about a month. Now the bounces are back.

I know baseball says 3 strikes are an "out", but I'm only giving them 2. The Matias is going in the trash as soon as my new Keychron K2 (with blue switches) gets here.

Wish me luck!


Update: It's been over 3 months now, and I am VERY happy with Keychron K2!

My only complaint is that the blue tooth times out even if I use an external power supply. Timing out blue tooth is a good thing when running on battery, but is unnecessary when it has external power. (NOTE: there is a  simple solution: don't use blue tooth. The same cable I'm connecting to an external power supply can simply be plugged into my laptop, at which point it's a wired keyboard. But I have some reasons for not wanting to do that. Oh well, I'm still very happy with the K2.)

Update 2: It's been over 7 months now, and the Keycron K2 is still going strong! It's a pleasure to use.