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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Luminar 1.0.2 - Powerful, adaptive, conf...
Luminar is the new full-featured image editor that adapts to the way you edit photos. Over 300 essential tools to fix, edit, and enhance your photos with comfort. The future of photo editing is here... Read more
WhatRoute 2.0.10 - Geographically trace...
WhatRoute is designed to find the names of all the routers an IP packet passes through on its way from your Mac to a destination host. It also measures the round-trip time from your Mac to the router... Read more
Slack 2.3.3 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.3.3: Fixed window zoom jumping back-and-forth OS X 10.9... Read more
Lens Blur 1.4.3 - True out-of-focus boke...
Lens Blur transforms your existing photo into true SLR-quality out-of-focus bokeh effect! Everyone needs a gorgeous personalized background for a social profile, blog, Web/UI design, presentation, or... Read more
CleanMyMac 3.6.0 - $39.95
CleanMyMac makes space for the things you love. Sporting a range of ingenious new features, CleanMyMac lets you safely and intelligently scan and clean your entire system, delete large, unused files... Read more
DEVONthink Pro 2.9.8 - Knowledge base, i...
DEVONthink Pro is your essential assistant for today's world, where almost everything is digital. From shopping receipts to important research papers, your life often fills your hard drive in the... Read more
MacFamilyTree 8.1 - Create and explore y...
MacFamilyTree gives genealogy a facelift: modern, interactive, convenient and fast. Explore your family tree and your family history in a way generations of chroniclers before you would have loved.... Read more
HoudahSpot 4.2.7 - Advanced file-search...
HoudahSpot is a powerful file search tool. Use HoudahSpot to locate hard-to-find files and keep frequently used files within reach. HoudahSpot will immediately feel familiar. It works just the way... Read more
TunnelBear 3.0.7 - Subscription-based pr...
TunnelBear is a subscription-based virtual private network (VPN) service and companion app, enabling you to browse the internet privately and securely. Features Browse privately - Secure your data... Read more
Garmin Express 4.5.0.0 - Manage your Gar...
Garmin Express is your essential tool for managing your Garmin devices. Update maps, golf courses and device software. You can even register your device. Update maps Update software Register your... Read more

Latest Forum Discussions

See All

Telltale Games really is working on a Gu...
Telltale Games' next episodic adventure is indeed Guardians of the Galaxy. A document tied to the voice actors strike suggested that the project was in the work, but now we have direct confirmation following an announcement at the Game Awards that... | Read more »
Amateur Surgeon returns to iOS and Andro...
Amateur Surgeon and its two sequels disappeared from the App Store some time and it was sad days for all. But now, just in time for the holidays, the Adult Swim favorite makes its joyous return in the shape of Amateur Surgeon 4, a remake with... | Read more »
The best board games on mobile
Sometimes you need to ditch all of the high speed, high action games in favor of something a little more traditional. If you don't feel like parting ways from your mobile device, though, there are still plenty of ways to get that old-school fix.... | Read more »
The best Facebook Messenger Instant Game...
Facebook's new Instant Games is now here, meaning you can play games with your friends directly via Facebook. It's a fun new way to connect with friends, of course, but it's also proving to be a solid gaming experience in its own right, with a... | Read more »
You can now play game's on Facebook...
Facebook launched its new Instant Games platform in an exciting new attempt to engage its user base. As a result, you can now play a number of different games directly through Facebook Messenger. All of these games run with HTML5, meaning you play... | Read more »
Apollo Justice Ace Attorney (Games)
Apollo Justice Ace Attorney 1.00.00 Device: iOS Universal Category: Games Price: $.99, Version: 1.00.00 (iTunes) Description: Court Is Back In Session Star as rookie defense attorney, Apollo Justice, as he visits crime scenes,... | Read more »
KORG iWAVESTATION (Music)
KORG iWAVESTATION 1.0 Device: iOS Universal Category: Music Price: $19.99, Version: 1.0 (iTunes) Description: A revolutionary new world of sound.The Wave Sequence Synthesizer for iPad - KORG iWAVESTATION | Read more »
Don't Grind Guide: Tips for becomin...
Don’t Grind is a surprising, derpy little one touch game with fun hand-drawn graphics. The goal is simple -- get the high score without being chopped to bits. That can be tough when you’re not used to the game, and that’s compounded by the fact... | Read more »
The top 4 Final Fantasy games on mobile
Final Fantasy XV is out today, and to celebrate we’re breaking down the best Final Fantasy games on mobile. Porting a game to mobile is always tricky business, but many of the early Final Fantasy games have made the transition quite well. Let’s... | Read more »
Swap Sword (Games)
Swap Sword 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

Parallels Toolbox 1.3 for Mac Offers 25 Singl...
Parallels has launched Parallels Toolbox 1.3 for Mac, an upgrade that adds five new utilities to the stand-alone application which was released in August and is available exclusively online at http... Read more
OWC Mercury Elite Pro Dual mini Ultra-Portabl...
OWC has introduced the new OWC Mercury Elite Pro Dual mini, a powerful yet ultra-portable dual-drive RAID solution. The new Mercury Elite Pro Dual mini packs phenomenal performance into a small... Read more
Clearance 13-inch Retina MacBook Pros availab...
B&H Photo has clearance 2015 13″ Retina Apple MacBook Pros available for up to $200 off original MSRP. Shipping is free, and B&H charges NY tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro: $... Read more
Roundup of 2016 13-inch 2.0GHz MacBook Pro sa...
B&H has the non-Touch Bar 13″ MacBook Pros in stock today for $50-$100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray (MLL42LL/A): $1449 $... Read more
New 13-inch 2.0GHz Space Gray MacBook Pro in...
Adorama has the new 13″ 2.0GHz Space Gray MacBook Pro (non-Touch Bar, MLL42LL/A) in stock for $1499 including a free 3-year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax... Read more
Finnair Adopts iOS Enterprise iPad Apps from...
Finnair and IBM have announced a first-of-its-kind agreement to utilize iOS enterprise apps from IBM to support the airline’s overall digital transformation. Finnair is focused on Asia-Europe traffic... Read more
Tech21 Launches Evo Go iPhone 7 Case Availabl...
Tech21 has announced the launch of the Evo Go case for Apple iPhone 7 and iPhone 7 Plus, exclusively at T-Mobile. Available online and at participating T-Mobile stores nationwide, Evo Go cases start... Read more
Apple Turns (RED) with More Ways to Join the...
In recognition of World AIDS Day, Apple is offering more ways than ever for customers to join (RED) in its mission to create an AIDS-free generation. Apple is the worlds largest corporate contributor... Read more
Deals on new 15-inch Touch Bar MacBook Pros,...
B&H Photo has new 2016 Apple 15″ Touch Bar MacBook Pro models in stock today with some available for $50 off MSRP, each including free shipping plus NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more
12-inch Retina MacBooks on sale for up to $10...
12-inch Retina MacBooks remain on sale at B&H Photo with models available for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only. B&H will also include a free copy... Read more

Jobs Board

*Apple* & PC Desktop Support Technician...
Apple & PC Desktop Support Technician job in Dallas TX Introduction: We have immediate job openings for several Desktop Support Technicians with one of our most Read more
*Apple* &Amp Pc Desktop Support Technici...
Apple & PC Desktop Support Technician job in Monroe, CT Introduction: We have immediate job openings for several Desktop Support Technicians with one of our most Read more
*Apple* Retail - Multiple Positions, Fort Wo...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions- Greenvi...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
US- *Apple* Store Leader Program - Apple (Un...
…Summary Learn and grow as you explore the art of leadership at the Apple Store. You'll master our retail business inside and out through training, hands-on Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.