The Robservatory

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Terminal

Watch a screen saver in the background

Another oldie but goodie, and it’s best demonstrated by example:

Yes, that’s a screen saver running in the background, behind whatever work you’re doing. And if nothing else, it’s a great example of the progress of our CPUs and GPUs since 2002. In the original hint, I noted:

On my G4/733 with the GeForce3, this is simply amazing. The new “flurry” screensaver is running right now on the destop at 1600×1200 in thousands, iTunes is playing, the ink recognition floater is open, and yet the CPU utilization is averaging at or below 50% of thereabouts

Today, I’m testing it on a 5K iMac (5120×2880) with a second connected 4K (3840×2160) display—a total of 23,040,000 pixels, or 12 times as many pixels as in 2002—with Flurry running on both screens, and the CPU usage is somewhere around 10% to 15%. (Flurry does send the iMac’s fans into a tizzy, though.) Other screen savers are even less intensive, and don’t send my iMac’s fans into high gear.

I can’t imagine actually working this way for very long, but it is kind of interesting. Here’s how to start (and more importantly, perhaps, stop) a background screen saver.

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A unique way to see the weather

Ever wanted a “light” weather check web site, free of ads and other visual clutter? One that you could maybe even use from Terminal? Then you want wttr.in.

Sure, you can use it from your browser, i.e. see the weather in Boston or Montreal, by just appending the zip/postal code of interest to the URL, i.e. http://wttr.in/95014. If you omit the location, wttr.in will get the location based on your IP address—for me, that’s never anywhere near correct when I’m at home, though.

What’s really neat is you can use it in Terminal, too, via curl:

$ curl wttr.in/80301

The output is graphical, but done so with text characters (click for zoomed version):

At a glance, you get a few days’ worth of conditions, including temperature range, wind speed, visibility, and precipitation. There’s even animation—check somewhere with thunderstorms, and you’ll see flashing lightning bolts.

There’s a help page that explains lots of other options, like forcing metric or US units, and looking at weather by airport code.

Install and use a non-GUI connection speed test tool

Yesterday on Twitter, Dave Hamilton tweeted…

What is this speedtest exactly? And what is brew, you may also be wondering? You may also be wondering why, if you have brew, Dave’s command doesn’t work…that’s because it’s actually brew install speedtest_cli…but I’m getting ahead of myself.

speedtest is a command line interface (i.e. Unix app run from Terminal) to the connection speed tests at Speedtest.net—you get the results without the fancy animated graphics. And Brew is “the missing package manager for macOS.” In other words, it’s an app to help you install (and uninstall) other apps.

Here’s how speedtest looks in its default mode—note that I’ve sped things up greatly for the GIF…

Much nicer to me, though, is the simplified version:

$ speedtest_cli --simple
Ping: 9.482 ms
Download: 94.23 Mbit/s
Upload: 68.66 Mbit/s

No animated dots, just three lines with the results. As you might expect if you read here regularly, I also wrote a Keyboard Maestro macro (of course I did!) that makes it really easy to run the simple version of the test, and does some editing of the output to simplify the display:

If you’d like to install speedtest (and maybe add the macro)—even if you don’t want to install Brew to do so—keep reading…

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Control inline video—and more—in Safari

This is another oldie but goodie from Mac OS X Hints, explaining how to enable the Debug menu in Safari. To do that, quit Safari, open Terminal, paste the following line, and press Return:

defaults write com.apple.Safari IncludeInternalDebugMenu 1

When you relaunch Safari, you’ll have a (really long) Debug menu on the far right of Safari’s menus. And just why might you want a Debug menu in Safari? Kirk McElhearn offers up one good reason:

Auto-play videos suck. They use bandwidth, and their annoying sounds get in the way when you’re listening to music and open a web page. …

But you can stop auto-play videos from playing on a Mac. If you use Chrome or Firefox, it’s pretty simple, and the plugins below work both on macOS and Windows; if you use Safari, it’s a bit more complex, but it’s not that hard.

In Safari, they key is the Debug menu, as Kirk points out. Go to Media Flags and select (activate) Disallow Inline Video, and that should be the end of auto-playing video. See Kirk’s blog post for ways to do the same in Firefox and Chrome.

Beyond auto-play video, though, there’s lots to geek out about in the Debug menu…

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Change the look of inactive Terminal windows

I tweeted this recently…

Things I did not know (or perhaps remember): Terminal lets you set the opacity and blur of inactive windows. (Profiles > Text > Background)

…but because I often forget about those things—the ephemeral nature of tweets being what it is—I figured I should post it here, too.

I have no idea when the feature appeared, but I only discovered it on February 27th, when I tweeted about it. You’ll find the window at right in Terminal’s preferences, on the Profiles tab—look in the Text section for a selected window, then click the color tile under Background. Check the box to set opacity and blur for inactive windows, and you’re done.

As I use a dark background in Terminal, I like this feature a lot. I’ve now got it set up to go transparent and fuzzy when inactive—this makes it basically vanish, so the dark background no longer grabs my eye.

At some point, I’ll dig through my virtual machines and figure out when this was added…who knows, maybe it’s been there for forever. In any event, I’m glad I stumbled across it the other day.

Open Unix man pages in their own Terminal window

A while back, I wrote about opening Unix man pages in Preview, and this is still my preferred method of browsing man pages. However, there may be times where Preview is overkill, and you want to stay in Terminal, maybe for a short help file such as that for ln. But opening a new window by hand is a bit of a pain, and tabs won’t work because you can’t see both the window and the man page at the same time.

While browsing the old Mac OS X Hints site, I found this nice solution: Open man pages in a new Terminal window, one that’s set up just for reading such pages. It looks something like this (though I’ve customized my setup; keep reading)…

Adding a few lines to your shell’s startup file makes opening these ‘in their own window’ man pages as easy as opening ‘regular’ man pages.

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Disable local Time Machine backups on laptops

Just noticed this post over on iMore…did you know that Time Machine automatically creates local backups on your laptop Mac? As described by iMore…

On Apple laptops, like the MacBook, MacBook Air, and MacBook Pro, Time Machine includes the added feature of creating local snapshots so that, if you disconnect your MacBook from its external hard drive, you’ll still have backups stored on your internal hard drive so you can recover data if you need to.

While the iMore article points out how to disable/enable the feature (sudo tmutil disablelocal or …enablelocal in Terminal), here’s a bit more detail not provided in the article.

First, this is not some hidden hack; you’re merely changing a setting using an Apple-provided command line interface to Time Machine. Apple, for whatever reason, chose not to include this setting in the GUI, but you’re not risking anything by making this change.

Second, you’ll find the local backups in a root-only folder named .MobileBackups, at the top level of your hard drive. You can—sort of—see how much space they take up by selecting About this Mac from the Apple menu, then clicking on the Storage tab. On my MacBook Air, which has a 2GB local backup, I see 4GB of purgeable space, which I assume includes that backup.

To get the actual size of the local backup, run this command in Terminal:

sudo du -h /.MobileBackups/

Provide your password, then wait a bit. The last line of the output will be the total size of the folder, stated in gigabytes…

…
…
 23M	/.MobileBackups//Computer/2017-02-16-092144
2.0G	/.MobileBackups//Computer
2.0G	/.MobileBackups/

And finally, if you disable this command, how do you know you’ve done so, months from now when you’ve forgotten about this? Time Machine itself will tell you, on its System Preferences panel. (Sorry for the low-res shot; I only have local backups enabled on my 11″ Air!)

As seen, after disabling the setting, Time Machine’s System Preferences panel will no longer list local backups as one of the tasks it performs.

See the launch date and time for any app or process

I was working on something with Peter about Moom and its disk usage (it doesn’t use much), and I was curious as to just how long Moom had been running on my Mac. I last rebooted my Mac a week ago, but I often quit and relaunch our own apps to run test versions.

Finder has this info, but that requires finding the running app in Finder. I wanted a quicker solution. In Activity Monitor (and ps in Terminal), you can see how much CPU time an activity has taken…

…but that doesn’t really help at all with knowing when the app (or process) launched. As long as you’re in Activity Monitor, you can get the information by doing the following:

  1. Click once on the app or process of interest.
  2. Press Command-I or click the small ‘i’ icon in the toolbar.
  3. In the new window that opens, click Sample, then wait.

When the sample is complete, you’ll see its output, and included there is the selected item’s launch date and time:

...
Analysis of sampling Moom (pid 89861) every 1 millisecond
...
Parent Process:  ??? [1]

Date/Time:       2017-02-15 07:41:18.611 -0800
Launch Time:     2017-02-13 19:44:11.957 -0800
...

That’s all fine if you’re in Activity Monitor, but a bit of a pain if you need to launch it, find the app, run a sample, etc.

As you might expect, there’s another way via Terminal: The lsappinfo command, which queries CoreApplicationServices about any app or process on your Mac.

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Create a workload for your CPUs

Over the weekend, I was testing how some of our apps work when the CPUs are busy. One way to load the CPUs is to rip a Blu-ray disc, but I was looking for a more controllable CPU load.

A quick search through the Mac OS X Hints archive (use this tip to search the site) found the answer from 15 years ago: Just say yes in Terminal to generate sizable CPU loads…

More specifically, use this command in Terminal:

yes > /dev/null &

If there’s an award for strangest Unix utility, yes might just be the winner. All it does is output y (or whatever you list after the y; the man page suggests an expletive) until you kill the task.

The above command sends the output (via the > redirect) to the null device, which discards it. The ampersand sends the job to the background, so you get your Terminal prompt back.

You can run this command multiple times, each loading the CPU even more heavily (the screenshot shows three yes tasks running). Keep an eye on Activity Monitor to see just how much CPU it takes—as shown above, it does a great job at loading the CPU.

You can kill the tasks by issuing the command killall yes in Terminal, or by quitting Terminal—you’ll be told that quitting will terminate the tasks.

Start Terminal sessions with a possibly-witty quote

Really long-time Unix users—as in mainframe-based Unix—are probably familiar with fortune. This silly little program grabs a random line from a collection of files holding quotes, sayings, jokes, etc. The Unix I used many decades ago would print an entry from fortune each time you started a new session. Here are some examples of what might greet me each time…

"It's a dog-eat-dog world out there, and I'm wearing Milkbone underware."
-- Norm, from _Cheers_

Mobius strippers never show you their back side.

All constants are variables.

Years ago, I had set up my Mac’s Terminal to output a fortune each time I opened a new session (window). At some point, though, I forgot to set it up on a new system, so it was gone. While fortune isn’t included in macOS’ Unix core by default, there are many ways to get it back, and it’s relatively simple to do so. Here’s one way…

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