TweetFollow Us on Twitter

Jun 02 Section 7

Volume Number: 18 (2002)
Issue Number: 06
Column Tag: Section 7

Some Basic Commands

by Rich Morin

Learn these first; the others can wait!

Before we look at any specific commands, we need to look at some fundamental differences between BSD terminal sessions and the ordinary Mac OS X (OSX) experience. Each interface has its advantages and disadvantages; by understanding these, you'll be able to use both interfaces more effectively!

  • Applications vs. Commands OSX applications tend to be highly interactive, providing customized environments for accomplishing particular tasks. BSD commands, in contrast, are generally run in "batch mode". The user issues the command, giving all of the needed information, waits for the result, and goes on.
  • Documents vs. Files OSX documents are generally encoded in an application-specific data format. Consequently, it is only by extra effort that other applications can make use of them. BSD files are expected to be useful to a wide range of commands. As a result, they are often formatted as ASCII text files, using white space (blanks, spaces, and newlines) to delineate internal data elements.
  • Subjects vs. Verbs In OSX, the user double-clicks on the icon for a document (subject) and the appropriate application (verb) starts up. Alternatively, s/he drags the document icon (subject) over to the application icon (verb). In BSD, the user types in the name of a command (verb), followed by assorted file names (subjects) and flags (adverbs).
  • Mice vs. Keyboards OSX employs a graphical user interface (GUI), using the mouse (trackball, ...) for nearly every action. Keyboard "shortcuts" are provided in some cases, but they are never required. In BSD, the situation is exactly reversed. The keyboard is used for everything; mouse "shortcuts" are used only occasionally.
  • Windows vs. Sessions OSX applications often put up multiple windows; actions taken in one window are expected to have ramifications in all of the other windows. Each BSD terminal session, in contrast, is expected to be independent of all of the other sessions.
  • Aqua vs. The Shell Aqua (including the Dock and the Finder) allows the user to navigate through the file system, manipulate documents and folders, and start up commands. The BSD "shell" (assisted by some common commands) provides equivalent capabilities, plus others (e.g., scripting, session logging). Of course, the user interfaces vary substantially!

Navigation Commands

As noted above, BSD command lines start with a verb, followed by some number of subjects and adverbs. Last month, we used the "man" command to view manual pages; let's use it again, trying out some variations.

[localhost:~] rdm% man 2 sync
[localhost:~] rdm% man 8 sync
[localhost:~] rdm% man sync

The sync(2) manual page describes a system call; sync(8), in contrast, is a system maintenance command. By specifying the section number, we can tell man which part of the manual to search. In most cases, there is no conflict, so the section number can be left off.

None of man's "arguments" are actually file names. Instead, they are hints that allow man to search assorted directories. The actual list of directories that man examines is specified by MANPATH, a BSD "environment variable". Environment variables and control files perform many of the functions of OSX preferences:

[localhost:~] rdm% echo $MANPATH
/Users/rdm/man:/usr/local/share/man:/usr/share/man

This tells us that man looks first under /Users/rdm/man (the user's personal man pages), /usr/local/share/man (this machine's "local" man pages), and /usr/share/man (OSX man pages). Let's wander over to the latter directory and take a look:

[localhost:~] rdm% cd /usr/share/man
[localhost:/usr/share/man] rdm% ls -F
man1/      man3/      man5/      man7/      whatis.db
man2/      man4/      man6/      man8/

The cd(1) command sets /usr/share/man as the "current directory" for this terminal session. This can save a lot of typing! For convenience, the shell puts the name of the current directory in the command line's "prompt string".

The ls(1) command provides a directory listing, appending slashes to directory names (as directed by the -F option). So far, the Finder seems a lot more convenient, but hang on a bit! Let's find out which directories have "sync" man pages:

[localhost:/usr/share/man] rdm% ls */sync*
man2/sync.2  man8/sync.8

The asterisk "wild cards" tell the shell to look through every subdirectory, looking for files whose names begin with "sync". Hmm; looks like the shell has some advantages when lots of items are involved. How many pages might that be, anyway?

[localhost:/usr/share/man] rdm% ls */* | wc -l
    2853

This command "pipeline" ran two commands, directing the "standard output" of one into the "standard input" of the other. The first command listed every file in every subdirectory; the second counted the number of lines in the first command's output. The result (2853) was something which neither base command was "designed" to produce.

This pipeline is actually a minuscule instance of a "shell script". BSD users frequently write scripts to automate repetitive tasks. Next month, we'll look at some more commands and some fancier ways of writing shell scripts.


Rich Morin has been using computers since 1970, Unix since 1986, and Mac-based Unix since 1986 (when he helped Apple create A/UX 1.0). When he isn't writing this column, Rich runs Prime Time Freeware (www.ptf.com), a publisher of books and CD-ROMs for the Free and Open Source software community. Feel free to write to Rich at rdm@ptf.com.

 
AAPL
$97.03
Apple Inc.
-0.16
MSFT
$44.40
Microsoft Corpora
-0.47
GOOG
$593.35
Google Inc.
-2.63

MacTech Search:
Community Search:

Software Updates via MacUpdate

Audio Hijack Pro 2.11.0 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more
Intermission 1.1.1 - Pause and rewind li...
Intermission allows you to pause and rewind live audio from any application on your Mac. Intermission will buffer up to 3 hours of audio, allowing users to skip through any assortment of audio... Read more
Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Microsoft Remote Desktop 8.0.8 - Connect...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
xACT 2.30 - Audio compression toolkit. (...
xACT stands for X Aaudio Compression Toolkit, an application that encodes and decodes FLAC, SHN, Monkey’s Audio, TTA, Wavpack, and Apple Lossless files. It also can encode these formats to MP3, AAC... Read more
Firefox 31.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals... Read more
Little Snitch 3.3.3 - Alerts you to outg...
Little Snitch gives you control over your private outgoing data. Track background activityAs soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 31.0 - Email client from Moz...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
Together 3.2 - Store and organize all of...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more
Cyberduck 4.5 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more

Latest Forum Discussions

See All

LEX Goes Free For One Day In Honor of Ne...
LEX Goes Free For One Day In Honor of New Update Posted by Jennifer Allen on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Thomas Was Alone Goes Universal, Slashes...
Thomas Was Alone Goes Universal, Slashes Price to $3.99 Posted by Ellis Spice on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Meerkatz Challenge Review
Meerkatz Challenge Review By Jennifer Allen on July 24th, 2014 Our Rating: :: FONDLY PUZZLINGUniversal App - Designed for iPhone and iPad Cute and challenging, Meerkatz Challenge is a fun puzzle game, particularly for fans of... | Read more »
Book Your Appointment with F.E.A.R. this...
Book Your Appointment with F.E.A.R. | Read more »
It Came From Canada: Epic Skater
For all the hate that it gets for being a pastime for slackers, skateboarding really does require a lot of skill. All those flips and spins take real athleticism, and there’s all the jargon to memorize. Fortunately for us less extreme individuals,... | Read more »
Cultures Review
Cultures Review By Jennifer Allen on July 24th, 2014 Our Rating: :: SLOW-PACED EMPIRE BUILDINGiPad Only App - Designed for the iPad Cute it might seem, but Cultures is a bit too slow paced when it comes to those pesky timers to... | Read more »
More Paintings Have Been Added to Paint...
More Paintings Have Been Added to Paint it Back! Posted by Jessica Fisher on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
The Order of Souls Review
The Order of Souls Review By Campbell Bird on July 24th, 2014 Our Rating: :: STORY GRINDUniversal App - Designed for iPhone and iPad The Order of Souls is a free-to-play, turn-based RPG with a genre-mixing art style, interesting... | Read more »
Revolution 60 Review
Revolution 60 Review By Jordan Minor on July 24th, 2014 Our Rating: :: LASS EFFECTUniversal App - Designed for iPhone and iPad Revolution 60 is a bold, cinematic action game with ambition to spare.   | Read more »
Matter (Photography)
Matter 1.0.1 Device: iOS Universal Category: Photography Price: $1.99, Version: 1.0.1 (iTunes) Description: Add stunning 3D effects to your photos with real-time shadows and reflections. Export your creations as photos or video loops... | Read more »

Price Scanner via MacPrices.net

Save on 5th generation refurbished iPod touch...
The Apple Store has Apple Certified Refurbished 5th generation iPod touches available starting at $149. Apple’s one-year warranty is included with each model, and shipping is free. Many, but not all... Read more
What Should Apple’s Next MacBook Priority Be;...
Stabley Times’ Phil Moore says that after expanding its iMac lineup with a new low end model, Apple’s next Mac hardware decision will be how it wants to approach expanding its MacBook lineup as well... Read more
ArtRage For iPhone Painting App Free During C...
ArtRage for iPhone is currently being offered for free (regularly $1.99) during Comic-Con San Diego #SDCC, July 24-27, in celebration of the upcoming ArtRage 4.5 and other 64-bit versions of the... Read more
With The Apple/IBM Alliance, Is The iPad Now...
Almost since the iPad was rolled out in 2010, and especially after Apple made a 128 GB storage configuration available in 2012, there’s been debate over whether the iPad is a serious tool for... Read more
MacBook Airs on sale starting at $799, free s...
B&H Photo has the new 2014 MacBook Airs on sale for up to $100 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels... Read more
Apple 27″ Thunderbolt Display (refurbished) a...
The Apple Store has Apple Certified Refurbished 27″ Thunderbolt Displays available for $799 including free shipping. That’s $200 off the cost of new models. Read more
WaterField Designs Unveils Cycling Ride Pouch...
High end computer case and bag maker WaterField Designs of San Francisco now enters the cycling market with the introduction of the Cycling Ride Pouch – an upscale toolkit with a scratch-free iPhone... Read more
Kingston Digital Ships Large Capacity Near 1T...
Kingston Digital, Inc., the Flash memory affiliate of Kingston Technology Company, Inc.,has announced its latest addition to the SSDNow V300 series, the V310. The Kingston SSDNow V310 solid-state... Read more
Apple’s Fiscal Third Quarter Results; Record...
Apple has announced financial results for its fiscal 2014 third quarter ended June 28, 2014, racking up quarterly revenue of $37.4 billion and quarterly net profit of $7.7 billion, or $1.28 per... Read more
15-inch 2.0GHz MacBook Pro Retina on sale for...
B&H Photo has the 15″ 2.0GHz Retina MacBook Pro on sale for $1829 including free shipping plus NY sales tax only. Their price is $170 off MSRP. B&H will also include free copies of Parallels... Read more

Jobs Board

Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full Read more
Senior Interaction Designer, *Apple* Online...
**Job Summary** Apple is looking for a hands on Senior…will be a key player in designing for the Apple Online Store. The ideal designer will have a Read more
*Apple* Sales Chat Rep - Apple (United State...
…is looking for motivated, outgoing, and tech savvy individuals who want to offer Apple Customers an unparalleled customer experience over chat. At Apple , we believe Read more
Mac Expert - *Apple* Online Store Mexico -...
…MUST be fluent in English and Spanish to be considered for this position At Apple , we believe that hard work, a fun environment, creativity and innovation fuel the Read more
*Apple* Industrial Design CAD Sculptor - App...
**Job Summary** The Apple Industrial Design team is looking for a CAD sculptor/Digital 3D modeler to create high quality CAD models used in the industrial design process Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.