TweetFollow Us on Twitter

Apr 02 Mac OS X

Volume Number: 18 (2002)
Issue Number: 04
Column Tag: Mac OS X

The BSD Man Pages

by Rich Morin

How to find them; how to read them.

Welcome

"Section 7", the name of this column, is also the shorthand term for the "Miscellaneous Information" section of the Berkeley Software Distribution's manual pages (known to their friends as the BSD "man pages"). This column will feature miscellaneous information on BSD-related aspects of Mac OS X, including application design, documentation, and even the politics of the developer and user communities.

Mac OS X is the most widely-disseminated version of BSD, but many Mac developers are a bit unclear on what BSD actually is. So, a word of explanation may be in order. BSD is a well-respected operating system, with a long history of solid engineering. Derived from Unix 32V, BSD is used for network servers, firewalls, and many other mission-critical applications.

Darwin (and thereby Mac OS X) is based on the FreeBSD and NetBSD distributions. As a result, it can take advantage of a well-developed operating system environment and thousands of "ported" applications from the FreeBSD Ports Collection. Clearly, BSD's solid technology and active developer community make a powerful contribution to the Mac OS X story.

Getting Started

BSD (and other Open Source) developers maintain several thousand "man pages" (manual pages), covering a wide range of topics. Because the pages are written by developers, they tend to be authoritative, consistently organized, current, detailed, and refreshingly honest. On the other hand, they also tend to be terse, tightly focused, and a bit unpolished in spots.

Consequently, reading man pages may not be the best way to approach a new and complex topic (e.g., NFS, socket programming), but it is an extremely handy way to learn about specific commands, remind yourself about forgotten details, etc. Once you've read a few man pages, I predict that you'll get addicted to their strong points; you may even (eventually) forgive their deficiencies.

Although it isn't critically necessary, you'll find it useful (and fun!) to have some Terminal windows on hand while you read this article. For one thing, you'll be able to see the actual output of the commands I'm describing; for another, you'll be able to try things out.

Using the Finder, navigate through the Applications and Utilities folders. When you find the icon for the Terminal Utility, drag it into the Dock. Now, double-click the icon twice, creating two Terminal windows. Unlike typical applications, these windows are not closely tied to each other. In fact, each Terminal window provides an independent BSD "session".

You should probably spend a few seconds arranging the windows, so that you can see them both at the same time. Also, stretch at least one of them vertically (keeping the width constant). This will let you see more of your commands' output without scrolling.

To view a particular man page, you must ask the system to run the "man" command, giving it the name of the page you want to see. We can try this out by asking for the man page that describes the "null" device:

[localhost:~] rdm% man null
NULL(4)         System Programmer's Manual           NULL(4)

NAME
     null - the null device

DESCRIPTION
     The null device accepts and reads data as any ordinary
     (and willing) file - but throws it away. The length of
     the null device is always zero.

FILES
     /dev/null

HISTORY
     A null device appeared in Version 7 AT&T UNIX.

Headings

As the example shows, each part of the man page is introduced by a descriptive heading. Some headings (e.g., NAME, DESCRIPTION) will show up on every man page; others (e.g., FILES, HISTORY) only appear when needed. Some, finally, are invented by the page's author. Here are some common headings, in the order they would normally appear on a man page:

  • NAME The following text gives the name(s) of the described item(s), followed by a terse description. In the case of commands, only one name will typically be given. In the case of library functions, however, there may be a long list of entry points.
  • SYNOPSIS The following text gives a (stylized) description of the normal usage mode for the item(s). In the case of commands, this will show the possible option flags; in the case of system calls and library functions, it will show representative declarations, etc.
  • DESCRIPTION The following text gives an extended description of the item(s), including options, usage considerations, etc. Some descriptions go on at great length.
  • RETURN VALUES The following text describes the return values for the item(s).
  • ERRORS The following text lists possible error conditions and resulting actions.
  • FILES The following text lists related files.
  • SEE ALSO The following text lists related man pages.
  • STANDARDS The following text lists applicable standards, sometimes discussing the degree to which the described item(s) comply.
  • BUGS The following text lists ways in which the command fails to meet the documentor's expectations. Some vendors find this section embarassing, so they rename or remove it. Feh!
  • NOTES The following text lists ancillary information which is not appropriate to any of the other sections.
  • HISTORY The following text tells where (i.e., in which BSD or Unix variant) the item first appeared, etc.

Paging

With all of this detail, some man pages can (and do :) go on for quite a while. In fact, multiple-page "man pages" are quite common. So, the man command is set up to let the reader "page" through the text. The default "pager" on Mac OS X is "more"; for a rundown on its capabilities, look at its man page!

[localhost:~] rdm% man more

Although more isn't very sophisticated, it does respond to the space bar (skip to the next page), the return key (move forward one line), "q" (quit), and a few other commands. If you want more features, try the GNU Project's "less" command (less is more, more or less):

[localhost:~] rdm% setenv PAGER less

Sections

The man pages cover a wide range of topics: administrative and user commands, C language interfaces, devices, etc. If all of the topics were simply sorted together, there would be name clashes. For instance, there is a passwd file, as well as a passwd command. To keep things straight, the man pages are divided into nine sections:

  • Section 1 (General Commands). These are commands that any user might enter from the command line or use in a "shell script". Some example commands include cd, ls, and rm.
  • Section 2 (System Calls). These are C language interfaces to kernel-provided services. Note that a system call, by definition, causes a context switch into the kernel. The application is halted until the system call completes. Some example system calls include close and open.
  • Section 3 (Library Functions). These are also C language interfaces, but the function runs (in general) with the application's context. Of course, some library functions make system calls, which do context switches, as described above. Some example library functions include fopen, scanf, and sqrt.
  • Section 4 (Devices and Device Drivers). These are the external interfaces to system devices. Some devices (e.g., /dev/null, /dev/tty) are intended for direct (command-line) use; others are only accessed by application or system-level code. Consequently, the descriptions in this section vary considerably in level and coverage.
  • Section 5 (File Formats). Many BSD activities are controlled or monitored by means of files. This section describes some of the critical files that an administrator might need to read or edit. Note, however, that Mac OS X uses different administrative mechanisms than most other BSD variants, so your mileage will definitely vary!
  • Section 6 (Games). Some BSD distributions include recreational programs; others do not. By placing these programs in a special area, the operating system eases monitoring and control of their use.
  • Section 7 (Miscellaneous Information). This section includes descriptions that are not tied to any given command, file, or function. Look here for high-level introductions, etc.
  • Section 8 (System Maintenance and Operation Commands). These are commands that the system administrator might enter from the command line or use in a "shell script". Some example commands include chown, fsck, and tunefs.
  • Section 9 (System Kernel Interfaces). These are C language interfaces to kernel-provided services. They differ from system calls in that they can only be called from inside the kernel. Thus, they are only of interest to kernel programmers. Mac OS X does not currently have this section, but FreeBSD does, so I expect it to show up eventually.

Navigation

Going back to the case of passwd, we see that the passwd command would be described in Section 1, while the passwd file would be described in Section 5. The specific man pages would normally be referred to as "passwd(1)" and "passwd(5)". By default, the man command will display the first page it finds, going in ascending order through the sections. You can make sure that you get passwd(5), however, by typing "man 5 passwd". Try it!

Unlike the hierarchical "help systems", as found on Cicso routers or operating systems such as VMS, man pages have no automated support for navigation. Some experimental variants use HTML to display man pages, turning SEE ALSO entries into hyperlinks. Most man systems, however, require that you do your own navigation.

Part of the reason for this lies in the sheer scale of the BSD command set. There are several hundred commands and thousands of functions. Trying to place them all in a meaningful hierarchy (or even defensible topical groupings) is not a trivial task! Nonetheless, some help is available.

To find a man page when you don't know the exact name, use apropos(1). It displays all the "NAME" lines that contain the specified text strings. If you are trying for a text string that contains non-alphanumeric characters, be sure to enclose the string in quotes. Otherwise, you'll get all the pages that match any "word" (i.e., sequence of non-blank characters) in the string. Here are some interesting uses of the apropos command; try them out!

[localhost:~] rdm% apropos device
[localhost:~] rdm% apropos dev
[localhost:~] rdm% apropos ‘(4)'
[localhost:~] rdm% apropos ‘file system'
[localhost:~] rdm% apropos file system

Although BSD provides several hundred commands, only a few are needed for everyday use. Next month, we'll look at some basic BSD commands, as well as a smattering of shell (command line interface) syntax.


Rich Morin has been using computers since 1970, Unix since 1983, and Mac-based Unix since 1985 (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
$116.47
Apple Inc.
+0.16
MSFT
$47.98
Microsoft Corpora
-0.72
GOOG
$537.50
Google Inc.
+2.67

MacTech Search:
Community Search:

Software Updates via MacUpdate

Cobook 3.0.7 - Intelligent address book....
Cobook Contacts is an intuitive, engaging address book. Solve the problem of contact management with Cobook Contacts and its simple interface and powerful syncing and integration possibilities.... Read more
StatsBar 1.9 - Monitor system processes...
StatsBar gives you a comprehensive and detailed analysis of the following areas of your Mac: CPU usage Memory usage Disk usage Network and bandwidth usage Battery power and health (MacBooks only)... Read more
Cyberduck 4.6 - 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
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Evernote 6.0.1 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
calibre 2.11 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital... Read more
Herald 5.0.1 - Notification plugin for M...
Note: Versions 2.1.3 (for OS X 10.7), 3.0.6 (for OS X 10.8), and 4.0.8 (for OS X 10.9) are no longer supported by the developer. Herald is a notification plugin for Mail.app, Apple's Mac OS X email... Read more
Firetask 3.7 - Innovative task managemen...
Firetask uniquely combines the advantages of classical priority-and-due-date-based task management with GTD. Stay focused and on top of your commitments - Firetask's "Today" view shows all relevant... Read more
TechTool Pro 7.0.6 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
PhotoDesk 3.0.1 - Instagram client for p...
PhotoDesk lets you view, like, comment, and download Instagram pictures/videos! (NO Uploads! / Image Posting! Instagram forbids that! AND you *need* an *existing* Instagram account). But you can do... Read more

Latest Forum Discussions

See All

Ubisoft Gives Everyone Two New Ways to E...
Ubisoft Gives Everyone Two New Ways to Earn In-Game Stuff for Far Cry 4 Posted by Jessica Fisher on November 21st, 2014 [ permalink ] | Read more »
Golfinity – Tips, Tricks, Strategies, an...
Dig this: Would you like to know what we thought of being an infinite golfer? Check out our Golfinity review! Golfinity offers unlimited ways to test your skills at golf. Here are a few ways to make sure your score doesn’t get too high and your... | Read more »
Dark Hearts, The Sequel to Haunting Meli...
Dark Hearts, The Sequel to Haunting Melissa, is Available Now Posted by Jessica Fisher on November 21st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Meowza! Toyze Brings Talking Tom to Life...
Meowza! | Read more »
Square Enix Announces New Tactical RPG f...
Square Enix Announces New Tactical RPG for Mobile, Heavenstrike Rivals. Posted by Jessica Fisher on November 21st, 2014 [ permalink ] With their epic stories and gorgeous graphics, | Read more »
Quest for Revenge (Games)
Quest for Revenge 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: The great Kingdom of the west has fallen. The gods ignore the prayers of the desperate. A dark warlord has extinguished... | Read more »
Threadz is a New Writing Adventure for Y...
Threadz is a New Writing Adventure for You and Your Friends Posted by Jessica Fisher on November 21st, 2014 [ permalink ] In the tradition of round-robin storytelling, | Read more »
SteelSeries Stratus XL Hardware Review
Made by: SteelSeries Price: $59.99 Hardware/iOS Integration Rating: 4 out of 5 stars Usability Rating: 4.5 out of 5 stars Reuse Value Rating: 4.25 out of 5 stars Build Quality Rating: 4.5 out of 5 stars Overall Rating: 4.31 out of 5 stars | Read more »
ACDSee (Photography)
ACDSee 1.0.0 Device: iOS iPhone Category: Photography Price: $1.99, Version: 1.0.0 (iTunes) Description: Capture, perfect, and share your photos with ACDSee. The ACDSee iPhone app combines an innovative camera, a powerful photo... | Read more »
ProTube for YouTube (Entertainment)
ProTube for YouTube 2.0.2 Device: iOS Universal Category: Entertainment Price: $1.99, Version: 2.0.2 (iTunes) Description: ProTube is the ultimate, fully featured YouTube app. With it's highly polished design, ProTube offers ad-free... | Read more »

Price Scanner via MacPrices.net

15″ 2.2GHz Retina MacBook Pro on sale for $17...
 B&H Photo has the 2014 15″ 2.2GHz Retina MacBook Pro on sale today for $1749. Shipping is free, and B&H charges NY sales tax only. B&H will also include free copies of Parallels Desktop... Read more
27-inch 3.5GHz 5K iMac in stock today and on...
 B&H Photo has the new 27″ 3.5GHz 5K iMac in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available... Read more
21-inch 1.4GHz iMac on sale for $979, save $1...
B&H Photo has the new 21″ 1.4GHz iMac on sale for $979.99 including free shipping plus NY sales tax only. Their price is $120 off MSRP. B&H will also include free copies of Parallels Desktop... Read more
13-inch 1.4GHz/256GB MacBook Air on sale for...
B&H Photo has lowered their price on the 13″ 1.4GHz/256GB MacBook Air to $1059.99 including free shipping plus NY sales tax only. Their price is $140 off MSRP, and it’s the lowest price for this... Read more
Save up to $400 with Apple refurbished 2014 1...
The Apple Store has restocked Apple Certified Refurbished 2014 15″ Retina MacBook Pros for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and shipping... Read more
New 13-inch 1.4GHz MacBook Air on sale for $8...
 Adorama has the 2014 13″ 1.4GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY & NJ tax only. Their price is $100 off MSRP. B&H Photo has the 13″ 1.4GHz/128GB MacBook... Read more
Apple Expected to Reverse Nine-Month Tablet S...
Apple and Samsung combined accounted for 62 percent of the nearly 36 million branded tablets shipped in 3Q 2014, according to early vendor shipment share estimates from market intelligence firm ABI... Read more
Stratos: 30 Percent of US Smartphone Owners t...
Stratos, Inc., creator of the Bluetooth Connected Card Platform, has announced results from its 2014 Holiday Mobile Payments Survey. The consumer survey found that nearly one out of three (30 percent... Read more
2014 1.4GHz Mac mini on sale for $449, save $...
 B&H Photo has lowered their price on the new 1.4GHz Mac mini to $449.99 including free shipping plus NY tax only. Their price is $50 off MSRP, and it’s the lowest price available for this new... Read more
Check Apple prices on any device with the iTr...
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**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 (ASC)- Retail S...
**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
Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
*Apple* Store Leader Program - College Gradu...
Job Description: Job Summary As an Apple Store Leader Program agent, you can continue your education as you major in the art of leadership at the Apple Store. You'll Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.