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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Logic Pro X 10.1.1 - Music creation and...
Apple Logic Pro X is the most advanced version of Logic ever. Sophisticated new tools for professional songwriting, editing, and mixing are built around a modern interface that's designed to get... Read more
VLC Media Player 2.2.0 - Popular multime...
VLC Media Player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, MP3, OGG, ...) as well as DVDs, VCDs, and various streaming protocols. It... Read more
Sound Studio 4.7.8 - Robust audio record...
Sound Studio lets you easily record and professionally edit audio on your Mac. Easily rip vinyls and digitize cassette tapes, or record lectures and voice memos. Prepare for live shows with live... Read more
LibreOffice 4.4.1.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
Freeway Pro 7.0.3 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
Cloud 3.3.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more
Cyberduck 4.6.5 - FTP and SFTP browser....
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
Firefox 36.0 - 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 and... Read more
Thunderbird 31.5.0 - Email client from M...
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
VOX 2.4 - Music player that supports man...
VoxIt just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features & support for all audio formats you should ever need... Read more

Get The Whole Story – Lone Wolf Complete...
Get The Whole Story – Lone Wolf Complete is Now Available and On Sale Posted by Jessica Fisher on February 27th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Who Wore it Best? The Counting Dead vs....
Like it or not, the “clicker” genre, popularized by cute distractions like Candy Box and Cookie Clicker, seems like it’s here to stay. So Who Wore it Best? takes a look at two recent examples: The Counting Dead and AdVenture Capitalist. | Read more »
Card Crawl, the Mini Deck Building Game,...
Card Crawl, the Mini Deck Building Game, is Coming Soon Posted by Jessica Fisher on February 27th, 2015 [ permalink ] Tinytouchtales and Mexer have announced their new game, | Read more »
Witness an all new puzzle mechanic in Bl...
Well, BlastBall MAX is not one of those games and is bucking trends such as timers, elements of randomness, and tacked-on mechanics in favor of pure puzzle gameplay. When you first boot up the game you’ll see a grid made up of squares that are each... | Read more »
This Princess Has a Dragon and She isn’t...
This Princess Has a Dragon and She isn’t Afraid to Useit. | Read more »
Mecha Showdown Review
Mecha Showdown Review By Lee Hamlet on February 27th, 2015 Our Rating: :: IN A SPINUniversal App - Designed for iPhone and iPad Mecha Showdown replaces traditional buttons with a slot machine mechanic in this robot fighting game,... | Read more »
Reliance Games and Dreamworks Unveil Rea...
Reliance Games and Dreamworks Unveil Real Steel Champions Posted by Ellis Spice on February 27th, 2015 [ permalink ] Reliance Games and Dreamworks have announced that a third game in | Read more »
Sum Idea Review
Sum Idea Review By Jennifer Allen on February 27th, 2015 Our Rating: :: TAXING NUMBERSUniversal App - Designed for iPhone and iPad Sum Idea is a fairly charming but taxing puzzle game.   | Read more »
A New Badland Update Brings Daydream Lev...
A New Badland Update Brings Daydream Levels to Co-Op Posted by Ellis Spice on February 27th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Slashing Demons Review
Slashing Demons Review By Lee Hamlet on February 27th, 2015 Our Rating: :: IT'S A LONG WAY TO THE TOPUniversal App - Designed for iPhone and iPad Slashing Demons lacks the depth or scope to take it beyond the point of being just... | Read more »

Price Scanner via MacPrices.net

Apple CEO Tim Cook to Deliver 2015 George Was...
Apple CEO Tim Cook will deliver the George Washington University’s Commencement address to GWU grads on May 17, at which time he will also be awarded an honorary doctorate of public service from the... Read more
Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
Save up to $50 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $50 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549 $50 off - 128GB iPad Air 2... Read more
16GB iPad Air 2 on sale for $447, save $52
Walmart has the 16GB iPad Air 2 WiFi on sale for $446.99 on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale price for online orders only,... Read more
iMacs on sale for up to $205 off MSRP
B&H Photo has 21″ and 27″ iMacs on sale for up to $205 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $1029 $70 off - 21″ 2.7GHz iMac: $1199 $100 off - 21″ 2.9GHz... Read more
Apple Takes 89 Percent Share of Global Smartp...
According to the latest research from Strategy Analytics, global smartphone operating profit reached US$21 billion in Q4 2014. The Android operating system captured a record-low 11 percent global... Read more
New Travel Health App “My Travel Health” iOS...
Rochester, Minnesota based Travel Health and Wellness LLC has announced that its new iOS app help safeguard the user’s health when traveling abroad — “My Travel Health” is now available on the Apple... Read more
Sale! MacBook Airs for up to $115 off MSRP
B&H Photo has MacBook Airs on sale for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 128GB MacBook Air: $799 100 off MSRP - 11″ 256GB MacBook Air: $999 $100... Read more
15-inch 2.0GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished previous-generation 15″ 2.0GHz Retina MacBook Pros available for $1489 including free shipping plus Apple’s standard one-year warranty. Their price is... Read more
Wither The iPad mini? End Of The Road Imminen...
AppleDailyReport’s Dennis Sellers predicts that the iPad mini is going to be left to wither on the vine, as it were, and then just allowed to fade away — a casualty of the IPhone 6 Plus and other... Read more

Jobs Board

Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Event Director, *Apple* Retail Marketing -...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global engagement strategy and team. Delivering an overarching brand Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.