Thursday, June 27, 2024


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.

Sunday, June 23, 2024

New Outlook: Security/Privacy Issues

 So, my old MacBook Air finally became unusable as my primary machine (the screen backlight burned out, possibly due to my having dumped a can of Diet Coke onto it). I can still VNC to it, so it will continue life as a "headless" Mac, but I needed a new laptop.

Based on my satisfaction with my work system, which is Windows and WSL2, I decided to go that route. But I didn't want to go with Office 365 and its annual subscription - it just seemed a bit steep to me. So I uninstalled Office 365 and bought Office Home and Business 2021.

At first it seemed fine, until I wanted to sync the contacts with my iCloud contacts. I didn't have tons of time to mess with it, and there isn't an easy way to do it, until I noticed there there is a "New Outlook" that I could turn on. I did, and lo and behold, it was able to download my iCloud contacts without a problem. Mind you, it is still not SYNCING, it just took a snapshot, but I don't update my contacts very often, so I'm calling it a win.

But then I noticed that "New Outlook" immediately downloads pics on emails. They claim it's secure because it uses a Microsoft server as a proxy -- i.e. the sender of the email cannot see my IP address -- but we know that there are tracking images whose file names are just identifiers for the recipient. So in effect, the sender is informed when I look at their email. I don't like that.

Worse yet - when I hover over a clickable link, it doesn't tell me what the URL is! THIS IS UNACCEPTABLE! I think it might be going through Microsoft's "safe URL" thing, which is better than nothing, but not nearly good enough. Now I have to right-click the link, copy it, and paste it into my browser to make sure it looks OK before hitting enter.

What's next? Does the new Outlook automatically execute code sent with the email? It used to, maybe they're doing that again.

Here I was all ready to admit that Microsoft was finally taking security and privacy seriously enough for me to switch; boy was I wrong. It will irk me no end to pay for Office 365 after having paid for Outlook 2021.

I guess I'll try to figure out a way to complain to MS, but I'm also confident my complaint will go nowhere.