MacTech Magazine Article Archives
Volume Number: 19 (2003)
Issue Number: 6
Column Tag: Mac OS X Programming Secrets
Mac OS X Programming Secrets
Mac OS X: Wading In Deeper
by Scott Knaster
This month we'll continue our peeking and poking around the edges of Mac OS X as we prepare for deeper voyages into OS X programming. In our last thrilling installment, we were messing around with Terminal and finding out about how it could enhance and enrich the lives of even those who spend most of their time above the GUI line. After cranking up Terminal, we discussed a few shell commands and introduced some useful tips for being more productive. We'll continue along those lines this time, exploring some more features of Terminal and its shell windows, then looking at a couple of lesser-known but useful shell commands.
Apple has done a good job of hiding most of the scars where Mac OS and Unix have been Frankensteined together, but there are still some design choices in which, shall we say, Mac user interface standards have not yet won the day. As you use Terminal, you probably noticed that things are just a little wacky here and there - Terminal hasn't quite completed the transition to becoming a full Mac application. For example, take a look in the Edit menu: there's no Undo command. What a giveaway! Let's take a look at some of the other cool tricks and odd quirks of Terminal.
Every shell window in Terminal includes a little picture of a torn square just above the scroll bar. See it? Hey, that's right where the split window control is many Mac apps. Could it be the same here? Yes, and no. It's a sort of mutant splitter. If you click on it, your window will indeed split into two panes (see Figure 1). However, only the top pane gets a scroll bar. The idea is that the bottom pane always shows the latest interaction between you and the shell, while you can scroll back in the top pane to any part of the shell session. You can even select text in the top pane, then drag and drop it into the bottom, where it shows up at the insertion point. To put the window back together in one piece, click the now-whole square that appears at the top of the lower pane.
Figure 1. Split Terminal window with one scroll bar and unsplit command.
Although window splitting is not done in the familiar Mac way in Terminal, there is a standard technique for fooling with colors. Last month, you might recall that we discussed changing the colors for the text and background in your shell windows by using the Color window. There are a couple of additional features worth mentioning for changing colors in shell windows. Take a look at the Color window in Figure 2. The Color window is a standard OS X component that you see in lots of apps, and you can even use it in your own creations, so everything we discuss here is also democratically available to you. Take a look at the tiny magnifying glass at the left side, near the top. You might not guess it, but that's a button. You can use it to pick a color you like from anywhere on the screen and use it in your shell windows.
Figure 2. Color window from Terminal
When you click the magnifying glass, the cursor changes to a bigger magnifier, and when you click elsewhere, the color under the magnifier's crosshair is sucked into the horizontal box next to the magnifier control in the Color window. Once the color is in that box, you can drag out of the box and drop the color into your shell windows to change the appearance of various things, depending on where you drop it. You can set the color of text, the background, bold text, or even the cursor rectangle. Try to be careful not to set the test and background to the same color: green on green (for example) text is hard to read. If that happens to you, just get another color into the box and drag it into the window. Either the text or the background will change color, and your text will be happily visible again.
Take a look at the bottom of the color window. You'll see a row of small white boxes. These boxes are sort of a scratch palette for your favorite colors. Each box can hold one color. To try it out, drag out of the long color box at the top of the window, and drop into a little square at the bottom. The color you dragged fills up the palette square you chose. You can repeat this for the other squares in the palette, putting other colors in the color box at the top and then storing them in the palette for safekeeping. And, the palette has a secret: it's actually much bigger than what you see in the color window. If you stretch the window to its maximum size, then drag the grabber at the bottom-center of the window down, you'll see that the palette can accommodate up to 300 colors. That should be enough for coloring shell windows, or even redecorating your house.
The last Color window feature we'll point out is the bar at the top that lets you select different methods of choosing your colors, including a color wheel, sliders that let you specify colors as RGB or other values, a set of palettes such as web safe colors, an image that contains colors you want to copy, or even a set of crayons. Figure 3 has a picture of the crayon picker, with some colors dropped into the palette at the bottom.
Figure 3. You can pick colors using crayons, and you can save your favorites in the palette at the bottom.
Window title bars in Terminal are another departure from standard Mac behavior. While most apps have already decided what they want to put in the title bar (usually the name of the document you're looking at), Terminal goes to great geeky lengths to let you customize the text in title bars. Using the File --> Show Info menu item to display the Terminal Inspector window (see Figure 4), you can choose from several options for your shell window titles, including these:
Figure 4. Terminal Inspector window lets you decide what goes in each shell window's title bar, which is an awesome responsibility you should not take lightly.
"Active Process Name" puts the name of the command being executed into the title bar. So, for example, if run an editor like vi in a window, Terminal will put vi into the window title.
"Shell Command Name" displays the name of the shell, such as bash or tcsh, that's running in the window.
"Dimensions" tells the number of character rows and columns displayed by the window, which lets you continue the fantasy that you're computing in 1972.
When you have multiple Terminal windows open, you can select each one with a command key shortcut: command-1, command-2, and so on. Checking "Command key" shows the window's shortcut in its title bar.
Changing any of these settings affects the frontmost Terminal window immediately. In fact, if you resize the window and you have the dimensions displayed, you'll see the number change live as you drag. Pretty slick for some old terminal program.
If you decide you like the settings so much that you want all Terminal windows to appear that way, click the "Use Settings as Defaults" button at the bottom of the window.
At Your Command
Now that we know how to customize our Terminal windows to a fine degree, let's take a look at a couple of shell commands and other tools that are useful both for using and programming with OS X. We'll start with a command that helps you learn more about what's going on in the vast active culture inside your Mac. The top command examines all the things running on your OS X Mac and provides information about them. To try it out, go to a Terminal window and type top and return. Here's what happened when I did it:
Processes: 63 total, 2 running, 61 sleeping..376 threads 14:56:20
Load Avg: 0.77, 0.57, 0.40 CPU usage: 64.9% user, 14.4% sys, 20.7% idle
SharedLibs: num = 7, resident = 2.03M code, 184K data, 520K LinkEdit
MemRegions: num = 7135, resident = 167M + 8.39M private, 116M shared
PhysMem: 58.3M wired, 284M active, 115M inactive, 457M used, 54.9M free
VM: 3.76G + 3.62M 13990(0) pageins, 12653(0) pageouts
PID COMMAND %CPU TIME #TH #PRTS #MREGS RPRVT RSHRD RSIZE VSIZE
1206 top 8.1% 0:06.02 1 14 18 300K 248K 596K 13.6M
1200 tcsh 0.0% 0:00.03 1 9 16 340K 492K 784K 5.73M
1140 tcsh 0.0% 0:00.03 1 10 16 348K 492K 792K 5.73M
1139 login 0.0% 0:00.28 1 12 33 248K 300K 572K 13.7M
1059 SystemUISe 0.0% 0:01.41 1 86 142 1.18M 4.77M 3.77M 99.7M
1058 Snapz Pro 0.9% 0:22.54 2 113 132 2.35M 8.23M 6.49M 107M
903 tcsh 0.0% 0:00.10 1 10 15 372K 492K 828K 5.73M
902 login 0.0% 0:00.36 1 12 33 236K 300K 568K 13.7M
827 slpd 0.0% 0:01.68 8 35 31 180K 364K 568K 17.8M
812 lookupd 0.0% 0:01.23 2 32 46 476K 384K 932K 14.9M
772 Microsoft 0.0% 2:10.00 12 148 296 15.2M 23.6M 11.5M 154M
768 Terminal 53.2% 1:48.60 5 102 437 4.55M- 14.6M 13.8M 116M
425 Microsoft 9.9% 18:43.86 5 100 448 33.1M 39.3M 47.1M 210M
424 SecurityAg 0.0% 0:00.79 1 53 96 1.11M 4.11M 2.73M 99.5M
423 Safari 0.0% 7:21.19 9 418 735 32.1M 18.1M 32.3M 232M
422 iTunes 0.0% 22:55.44 12 185 282 11.7M 12.9M 20.6M 135M
421 AppleSpell 0.0% 0:00.47 1 18 22 440K 848K 1.13M 15.0M
417 iChatAgent 0.0% 0:04.10 5 71 67 844K 1.69M 2.37M 81.8M
416 Fax Assist 0.0% 0:00.25 1 51 68 560K 2.75M 1.27M 95.2M
415 MSN Messen 0.9% 4:02.51 5 81 108 876K 4.47M 2.94M 99.5M
414 Fax Server 0.0% 0:00.28 1 53 71 600K 3.25M 1.68M 96.2M
413 MicrosoftM 0.0% 0:02.21 1 43 33 216K 788K 708K 78.7M
411 MSN Messen 1.8% 21:02.39 5 134 169 3.41M 11.6M 8.82M 121M
410 iChat 0.0% 2:37.36 4 144 284 5.47M 11.8M 10.2M 125M
409 NetNewsWir 0.0% 12:05.59 2 1884 231 21.1M 12.2M 29.6M 133M
408 OmniOutlin 0.0% 1:56.60 3 87 209 8.61M 8.56M 13.7M 121M
406 Microsoft 0.9% 0:45.08 2 69 135 4.76M 6.38M 6.87M 104M
404 Finder 0.0% 0:15.61 1 84 147 3.29M 13.1M 8.92M 129M
402 Dock 0.0% 4:35.44 2 127 168 1.58M 11.6M 8.43M 154M
396 pbs 0.0% 0:01.43 2 30 27 400K 856K 1.01M 14.4M
391 httpd 0.0% 0:00.00 1 8 74 4K 796K 80K 15.6M
390 httpd 0.0% 0:02.00 1 19 72 32K 796K 664K 15.1M
389 AppleFileS 0.0% 0:04.69 2 31 24 592K 852K 824K 18.4M
364 cron 0.0% 0:00.09 1 8 15 40K 232K 108K 13.5M
347 DirectoryS 0.0% 0:01.58 3 57 152 548K 1.40M 1.54M 21.4M
343 cupsd 0.0% 0:07.58 1 8 25 1.36M 604K 1.63M 16.3M
334 xinetd 0.0% 0:00.02 1 10 15 36K 212K 76K 1.45M
332 inetd 0.0% 0:00.00 1 8 13 24K 208K 64K 1.28M
325 ntpd 0.0% 0:01.64 1 8 15 96K 288K 244K 1.52M
323 loginwindo 0.0% 0:04.25 4 159 150 2.25M 5.18M 4.00M 97.0M
314 smbd 0.0% 0:00.01 1 8 21 328K 212K 76K 15.5M
312 automount 0.0% 0:00.05 2 22 21 128K 268K 392K 14.7M
311 sshd 0.0% 0:00.13 1 8 16 40K 212K 80K 1.83M
309 coreservic 0.0% 0:02.01 3 104 92 1.06M 6.82M 6.77M 36.6M
294 nfsiod 0.0% 0:00.00 1 8 12 0K 220K 52K 1.27M
293 nfsiod 0.0% 0:00.00 1 8 12 0K 220K 52K 1.27M
292 nfsiod 0.0% 0:00.00 1 8 12 0K 220K 52K 1.27M
291 nfsiod 0.0% 0:00.00 1 8 12 0K 220K 48K 1.27M
261 netinfod 0.0% 0:01.22 1 7 30 124K 296K 284K 1.66M
243 mDNSRespon 0.0% 0:00.57 2 40 29 904K 260K 676K 14.4M
240 crashrepor 0.0% 0:00.00 1 14 14 32K 208K 72K 13.3M
229 syslogd 0.0% 0:00.30 1 7 13 64K 220K 140K 1.28M
189 autodiskmo 0.0% 0:02.29 191 59 410 1.13M 624K 1.31M 113M
185 Window Man 11.8% 29:55.34 2 323 870 13.2M+ 59.7M 59.7M+ 249M+
181 ATSServer 0.0% 5:45.23 2 47 230 824K 6.03M 2.63M 47.0M
164 SecuritySe 0.0% 0:03.61 1 58 23 220K 792K 732K 14.9M
111 configd 0.0% 0:52.11 3 132 150 548K 900K 1.02M 16.3M
77 dynamic_pa 0.0% 0:00.00 1 10 15 48K 216K 92K 1.29M
73 update 0.0% 0:04.89 1 7 13 32K 212K 84K 1.26M
51 kextd 0.0% 0:01.95 2 18 22 280K 524K 340K 15.3M
2 mach_init 0.0% 0:00.53 2 203 15 88K 224K 176K 1.80M
1 init 0.0% 0:00.02 1 9 12 52K 216K 232K 1.28M
0 kernel_tas 0.0% 6:24.29 28 0 - - - 49.2M 475M
0 idle_threa 26.3% 11:53:50
Gosh, that's a lot of stuff. I sure hope there's nothing embarrassing in there.
top gives you an ever-updating list of all the processes running in your Mac, with lots of juicy information about each of them. If you keep an eye on the top display, you'll notice that it keeps changing, producing new numbers every second. If you launch any other apps, or even if you open a new shell window or do anything else that starts a process, you'll see a new entry in the list. Similarly, processes drop off the list when they're stopped, as when you quit an application or close a Terminal window.
Processes are listed in reverse of their launch order, newest first. The numbers in the first column are the process IDs, followed by the name of the process or application. Obviously, there's an enormous amount of information here. We'll go over some of the most interesting items here, and refer you to the man entry for full details.
If you're playing along at home, and your don't seem to have as many processes listed on your computer, you might not be getting the full picture. To make sure you see as much of the top display as possible, stretch your Terminal window out to its maximum size, and then use the Font menu to make the window's font small enough that you see all the processes. You know you're seeing it all if you can see process 0, idle_thread, listed at the bottom.
Coming Out On Top
Now let's make some sense of this display, starting with the header that appears before the list of processes. The first line of output tells you the number of processes and threads, while the value at the end of the line is simply the time of day, so you can use top as a super-complicated clock if you like. Another interesting value in the header is the CPU usage in the second line. In this example, the CPU is 20.7% idle, which is actually quite busy - usually, you'll find the idle value much higher than that. For fun, you can quickly whip the mouse pointer around the screen, and you'll see the idle value go down as the CPU sweats to keep track of it.
The meaty part of the top display is the big list of processes. As we mentioned earlier, the first two columns are the process ID and the "command" name, which usually includes an entry for every running application. We can also see that several shell commands have their own listings, even though they aren't applications. These include several tcsh shells and top itself. The first value after the command name is the percentage of CPU time being hogged by that process. For example, you can see that Terminal was grabbing a whopping 53.2% of the CPU's time when this list was printed. Even for the active application, that's quite a large fraction. You can use top to help determine if any particular app, including one you're programming, is taking up more than its share of CPU time.
What else is interesting in this list? Note that the next item under Terminal is using 9.9% of the CPU time. The name of that process is...Microsoft? Microsoft what? Word, Excel, MSN? Unfortunately, there is no way to tell. A regrettable artifact of Mac OS X's Unixness is that there isn't enough room for process names that are as long as some Mac application names. One way to figure out which Microsoft application is which is to bring one to the front, then start typing. One of the apps will suddenly start taking a lot more CPU time: that's the active one. On the other hand, if you see any application that takes a lot of CPU time even when it's not frontmost, you might be able to improve your Mac's performance by replacing that app.
top includes a couple of command line options that you might find useful. The -u option keeps the list of processes constantly sorted according to usage, rather than launch order. This makes you a little crazy but is kind of fun to watch and ensures you know which tasks are using the most CPU time. You might also like to try the -s option, which takes a value after the s to indicate how many seconds should pass before updating the display.
That's A Man, Baby
To become more adept at Unix commands, I'll repeat that you should make frequent use of the man command. This command gives you pages from the Unix online "manual", which was a really clever idea back in 1906 when Unix was invented and is now sometimes barely adequate to help you figure out what's going on. The man documentation wasn't written by the literate folks at Apple, but you'll need it sometimes to get you through the night.
Welcome To The Machine
We'll finish by talking about one more little shell command of interest: machine. This command works under Mac OS X to tell you which CPU your computer is using: if the Mac has a G3, you get ppc750, and a G4 returns ppc7450. These are Motorola's part numbers for the chips, useful if you ever find yourself wanting to order CPU manuals from Motorola.
Finally, be sure you check this command's man page. If you do, you'll find the less-than-enlightening guidance that "The machine command is currently under development." But the real fun is that you get to type man machine.
Scott Knaster has been writing about Macs for as long as there have been Macs. Scott's books How To Write Macintosh Software and Macintosh Programming Secrets were required reading for Mac programmers for more than a decade. Scott wrote developer books for General Magic and worked on Mac software for Microsoft. Scott's books have been translated into Japanese and Pascal. Scott has every issue of Mad magazine, which explains a lot.