TweetFollow Us on Twitter

Mac in the Shell: The man Show

Volume Number: 23 (2007)
Issue Number: 05
Column Tag: Mac in the Shell

Mac in the Shell: The man Show

Learning shell utilities with and without man

By Edward Marczak

Introduction

Documentation. The ugly reality is that it's usually an afterthought for a project, if completed at all. We like to code, we like to connect systems, but rarely do we like to document the work. man ("manual") pages, the built-in documentation system, have thousands of entries for shell utilities. Depending on the author, these entries range from well-written, humorous and pleasurable reading, down to sparse, terse and frustrating. Sometimes, the simple act of giving usage examples would make all the difference in usefulness and clarity. While I can't cover every shell utility here, I would like to point out some that you should know about, but that may not have the best documentation or just lack examples.

networksetup

Just as the name implies, networksetup is a utility to configure the network interfaces on a Mac OS X machine. There's no man page for this one at all. By default, it's not even in your path. Currently, under OS 10.4 ("Tiger"), you'll find networksetup located at: /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Support/networksetup (whew!). There is, though, a usage statement printed if you run the command but lists no options and provides no examples.

Since OS X uses configd to inform the system of its current configuration state, the old-school utilities, such as ifconfig don't really work too well. Oh, yes, they can read the current state of the network, but setting it is another matter. This will work for a little bit, at least until configd receives a change event and reconfigures things for you.

networksetup uses terminology that is closer to the OS X GUI than traditional devices, too. First thing you typically need to figure out are the names of the network services being offered -- a.k.a. the interface names:

# networksetup -listallnetworkservices
An asterisk (*) denotes that a network service is disabled.
Bluetooth
Built-in Ethernet
Built-in FireWire
AirPort
Parallels Host-Guest
Parallels NAT
VPN (L2TP)

(You do, by the way, need admin level privileges to run this utility). You'll note that these names correspond to the names in the Network System Pane:


Figure 1 -- Interface names

If you rename the interface in the Network Pane, networksetup will see it that way, too. A possibly more useful list, if you're on a machine that you're not familiar with yet, is gained from the -listnetworkservice order switch. It shows both the interface name and the order that OS X uses it:

# networksetup -listnetworkserviceorder
An asterisk (*) denotes that a network service is disabled.
(1) Bluetooth
(Hardware Port: Bluetooth, Device: Bluetooth-Modem)
(2) Built-in Ethernet
(Hardware Port: Built-in Ethernet, Device: en0)
(3) Built-in FireWire
(Hardware Port: Built-in FireWire, Device: fw0)
(4) AirPort
(Hardware Port: AirPort, Device: en1)
(5) Parallels Host-Guest
(Hardware Port: Parallels Host-Guest, Device: en2)
(6) Parallels NAT
(Hardware Port: Parallels NAT, Device: en3)
(7) VPN (L2TP)
(Hardware Port: Windows L2TP, Device: )

This list is a great reminder that routes may be overridden by the order of interfaces.

Well, how about setting up the device? There are switches that act like each of the settings in the GUI:


Figure 2 -- How d'ya like your interface?

Probably of most interest is "-setmanual". To configure the built-in Ethernet interface to have an IPv4 address of 192.168.50.77, with a subnet mask of 255.255.255.0 and a default gateway of 192.168.50.1, you'd use this:

networksetup -setmanual "Built-in Ethernet" 192.168.50.77 255.255.255.0 192.168.50.1

One nice trick that doesn't seem apparent from the usage help, but has worked for me (up through 10.4.9), is that the router is optional. This is critically important when you're configuring an interface that will be active along with another.

The second option in our list is "-setmanualwithdhcprouter". This is just like "-setmanual", without being able to specify the subnet or router:

networksetup -setmanual "Built-in Ethernet" 192.168.50.77

Setting an interface to use DHCP is simple:

networksetup --setdhcp "AirPort"

You can also supply a client id after the interface name, if necessary. You can also clear the current client id by using "Empty" as the client ID name.

Similar to "-setdhcp" is "-setbootp". The command is the same as "-setdhcp", however, bootp doesn't support a client id, so, nor does this command.

Finally, "-setnetworkserviceenabled" roughly corresponds to "Off". This can turn the service "off" or "on":

networksetup -setnetworkserviceenabled "Bluetooth" off

If you run this while the Network Pane is open in the GUI, the GUI will alert you with, "Your network settings have been changed by another application" -- just something to be aware of. It then places an asterisk next to the name of the interface when using "-listallnetworkservices" and "-listnetworkserviceorder".

Finally, there are some very useful Airport specific commands. Different than enabling or disabling the interface, you can also turn power to the Airport off completely:

networksetup -setairportpower off

Of course, you can turn it back on with the same switch and a parameter of "on". You can also check the current state with "-getairportpower".

Of greater use, though, is the ability to programmatically set which network to connect to, using "-setairportnetwork":

networksetup -setairportnetwork "BigNet" SekurePa$$wd

Here too, you can find out the current state with a 'get' variant:

networksetup -getairportnetwork
Current AirPort Network: SuperAirNet

The networksetup command is very powerful and very thorough! In addition to the options I covered here, you can do anything that you can do in the GUI: create VLANs, turn AppleTalk on or off, set proxy configuration and more. It's a good command to be familiar with for scripting, remote setup and just to do things the "OS X way!"

scp

"scp" is the secure copy program. It's part of the ssh suite, which means that any remote machine you can connect to via ssh, you can also copy programs to and from. While there is a man page for this one, it doesn't have example usage. Also, I find that not enough people know about or use it -- even those who use ssh on a regular basis. scp is simple, really. To copy a local file to a remote machine, use this:

scp local_file my_id@server.example.com:/path/to/file/filename

You'll be asked for a password from the remote machine. Then, given permission on the remote, you'll see a progress meter that shows the file in transit. In my example, "my_id" is the id you use on the remote machine. (For those of you that may want to date yourself, unlike ssh, scp does not accept the "-l" (ell) switch to pass in your credentials -- a switch that ssh supplies to make the transition from telnet easier!).

The colon character (":") separates the hostname from the path. This can be a relative path, too. The starting location is the remote id's home directory. Also, like ssh, if unspecified, your current id is supplied. So, if I wanted to copy a file to my home directory on my test box, I could simplify the command down to this:

scp local_file lycaeum.radiotope.com:

Do note the trailing colon character. Without it, you'll just make a local copy of the file -- in this case, named "lycaeum.radiotope.com".

To copy from a remote machine, just reverse the order of the files, putting remote information first. To copy "filename" from the remote to your machine as "local_file", try this:

scp my_id@remote.example.com:/path/to/file/filename local_file

Again, to use the same name as the remote, simply omit it on the local side:

scp lycaeum.radiotope.com:program-4.7.6.tar.gz ./

If you're thinking of using this in an unattended script, you'll need to authenticate via keys so that you're not prompted for a password. While there are plenty of examples on the web of how to do this, for the sake of completeness, here is the short version:

Open up a shell on the local computer, and log into the correct local account.

Generate a public-private keypair by typing "ssh-keygen -t rsa". Leave the passphrase empty. This creates the files "id_rsa" and "id_rsa.pub" in the .ssh directory in this account's home directory.

Copy only id_rsa.pub to the remote machine using scp.

Login to the remote machine, and add the contents of id_rsa.pub to ~/.ssh/authorized_keys. You can use redirection to do this, as the authorized_keys file may already exist: cat id_rsa.pub >> ~/.ssh/authorized_keys

Logout of the remote machine, and test the setup using ssh. Try to ssh back into the remote machine. This time, you should not be prompted for a password.

Using keys in this manner, you'll be able to setup scp copies in an unattended script.

ssh and File Copy Programs

You may use ssh every day. You may use some of its more advanced features. But it is impossible to Know ssh. For every feature that you use, there seems to be another that you didn't know even existed. Did you know that ssh accepts input on standard in (stdin) and will simply shove it through the tunnel, popping it out on the other side?

What does that mean to us? Well, you can just gather up your data and pipe it to ssh:

tar czf - /path/to/file | ssh

Of course, we need to do something with it once it gets to the other side. How about expanding it somewhere? Let's imagine that we wanted to tar up the local /www directory and get it to a remote machine with its hierarchy intact:

tar czf - /www | ssh "cd /; tar xzfvp -"

Now, tar is a very nice solution -- most of the time. It's had a bit of an on-again off-again brokenness to it under OS X regarding resource fork copying. As I write this article, using OS X 10.4.9 Intel, tar works very nicely for copying resource forks. One other huge advantage to tar is that it preserves dates on copy. But, in fact, ditto will do this too, along with preserving all of the other OS X-specific data that it normally does. A simple example is a webloc file, which typically is resource-fork only (text clippings are also resource fork only). Fire up Safari, load a page and then drag the icon from the location bar to your desktop. Now you have a resource fork only file to work with:

$ cd Desktop
$ ls -l Weather\ Map.webloc 
-rw-r--r--   1 marczak  marczak  0 Apr 15 08:33 Weather Map.webloc
$ ls -l Weather\ Map.webloc/..namedfork/rsrc
-rw-r--r--   1 marczak  marczak  837 Apr 15 08:33 Weather Map.webloc/..namedfork/rsrc

Let's move this file to a remote machine using ditto. Again, I'm going to copy to my test server (lycaeum) and rely on the fact that by default, ssh plops me into my home directory. If you want to write the data elsewhere, replace the "./" path with one that suits you (and you have permission for). Here it is:

ditto -c Weather\ Map.webloc - | ssh lycaeum.radiotope.com ditto -x - ./

Log into the remote server and check out the date, time and other file attributes -- they'll all stay intact (however, not ACLs, as expected).

Machine Info

I'll leave you with two commands that can display information about the software and hardware on a given machine: sw_vers and system_profiler. Not that these are complex or need a lot of explanation, but just to know that they exist. If I could count all of the times I see a question about getting system information on a tech mailing list, I probably wouldn't be writing this!

sw_vers is the simpler of the two. With no options, it dumps out the product name, version and the build number:

$ sw_vers 
ProductName:    Mac OS X Server
ProductVersion: 10.4.9
BuildVersion:   8P135

You can pass in switches to limit the amount of information returned:

$ sw_vers -buildVersion
8P135

Filtering the information is certainly useful if you need this information in a script.

system_profiler is the shell equivalent of the GUI System Profiler.app. Like sw_vers, just used on its own, it gives you a good deal of info. Try it! (There's way too much output to print here). You can parse through this data on your own. If you're only looking for a specific bit of info, you can pass in filters that do just this:

$ system_profiler SPMemoryDataType
Memory:
    BANK 0/DIMM0:
      Size: 2 GB
      Type: DDR2 SDRAM
      Speed: 667 MHz
      Status: OK
    BANK 1/DIMM1:
      Size: 1 GB
      Type: DDR2 SDRAM
      Speed: 667 MHz
      Status: OK

You can get a list of data types with the "-listdatatypes" switch. If you want more than one type at once, go ahead and pass in those types:

system_profiler SPDisplaysDataType SPAirPortDataType SPPowerDataType

sw_vers and system_profiler are both great commands when accessing a remote machine that you may not be familiar with -- especially when someone is sitting at the console and you don't want to ask them for the information!

Summary

I regularly use the commands and techniques presented here. While the information is typically in the man page, useful examples don't always accompany that information. Sometimes, you just need to experiment with a command -- on a test system, of course -- until you have it figured out. Sometimes there are alternatives to man. Many GNU utilities have an info page that's different than the man page, if one even exists. Try "info emacs", for example. Press 'q' to get out of info's display. Of course, MacTech and publications like it (are there any?) present good alternatives to man pages as well. I hope this article was a good step in that direction for anyone reading it.

Media of the month: well, it's not going to be a Leopard title, as we're going to see a little delay there! However, there's plenty to be read before then. Don't get all stressed out about it. Instead, find some entertaining reading, like the "Lord of the Rings" trilogy. OK, not necessarily short reading, but I'm always surprised by how many people have not read these books. The movies were fine, but the books capture something different.

Until next month, enjoy!


Ed Marczak owns Radiotope, a technology consulting company that brings enterprise solutions to small and medium sized businesses. He is also the Executive Editor for MacTech magazine. Outside of technology, Ed likes to spend time with his family, and to practice counting.

 
AAPL
$567.77
Apple Inc.
+43.02
MSFT
$39.86
Microsoft Corpora
+0.17
GOOG
$525.16
Google Inc.
-1.78

MacTech Search:
Community Search:

Software Updates via MacUpdate

Ember 1.5.1 - Versatile digital scrapboo...
Ember (formerly LittleSnapper) is your digital scrapbook of things that inspire you: websites, photos, apps or other things. Just drag in images that you want to keep, organize them into relevant... Read more
Cyberduck 4.4.4 - 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
TechTool Pro 7.0.3 - 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
MacFamilyTree 7.1.6 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
EtreCheck 1.9.9 - For troubleshooting yo...
EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support... Read more
TeamViewer 9.0.28116 - Establish remote...
TeamViewer gives you remote control of any computer or Mac over the Internet within seconds, or can be used for online meetings. Find out why more than 200 million users trust TeamViewer! Free for... Read more
DiskAid 6.6.3 - Use your iOS device as a...
DiskAid is the ultimate transfer tool for accessing the iPod, iPhone or iPad directly from the desktop. Access data such as: music, video, photos, contacts, notes, call history, text messages (SMS),... Read more
Viber 4.1.0 - Send messages and make cal...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device,... Read more
Apple iOS 7.1.1 - The latest version of...
The latest version of iOS can be downloaded through iTunes. Apple iOS 7 brings an all-new design and all-new features. Simplicity Simplicity is often equated with minimalism. Yet true simplicity is... Read more
1Password 4.3 - Powerful password manage...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more

Latest Forum Discussions

See All

Pen & Ink Review
Pen & Ink Review By Jennifer Allen on April 24th, 2014 Our Rating: :: CONVENIENT ARTISTRYiPad Only App - Designed for the iPad Pen & Ink is an ideal way to sketch down some visual ideas or simply spark your imagination.   | Read more »
Sonic & All-Stars Racing Transformed...
Sonic & All-Stars Racing Transformed Now Free, to Add New Iconic Characters and Elements Posted by Tre Lawrence on April 24th, 2014 [ | Read more »
Soccer Rally 2 Review
Soccer Rally 2 Review By Carter Dotson on April 24th, 2014 Our Rating: :: GOALKEEPINGUniversal App - Designed for iPhone and iPad Soccer Rally 2 is the most serious vehicular soccer game ever created.   | Read more »
Galaxy Conquerors Review
Galaxy Conquerors Review By Jennifer Allen on April 24th, 2014 Our Rating: :: RETRO SHOOTINGUniversal App - Designed for iPhone and iPad Old school shooting is fun but inaccurate in Galaxy Conquerors.   | Read more »
Yomi Review
Yomi Review By Rob Thomas on April 24th, 2014 Our Rating: :: C-C-C-COMBO BREAKERiPad Only App - Designed for the iPad Round One – Fight! No quarters required for this iOS adaptation of a tabletop adaptation of the arcade fighting... | Read more »
Injustice: Gods Among Us Updated with Ne...
Injustice: Gods Among Us Updated with New Characters, Leaderboards, Gear, and Online Multiplayer Posted by Rob Rich on April 24th, 2014 [ | Read more »
Spin It Review
Spin It Review By Jordan Minor on April 24th, 2014 Our Rating: :: SPIN ME RIGHT ROUNDUniversal App - Designed for iPhone and iPad Spin It has a fine puzzle game model, but its execution lacks energy.   | Read more »
Productivity App NoteSuite is Having its...
Productivity App NoteSuite is Having its Biggest Sale Ever, Just for One Week Posted by Rob Rich on April 24th, 2014 [ permalink ] | Read more »
Wayward Souls Review
Wayward Souls Review By Carter Dotson on April 24th, 2014 Our Rating: :: CARRY ON, WAYWARD SONUniversal App - Designed for iPhone and iPad Wayward Souls is a roguelike-inspired action-RPG that sets a high bar for other games to... | Read more »
The Sandbox Gets Update, Receives New Ca...
The Sandbox Gets Update, Receives New Campaign and New Elements Posted by Tre Lawrence on April 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »

Price Scanner via MacPrices.net

Strong iPhone Sales Drive Apple Record March...
Apple on Wednesday announced financial results for its fiscal 2014 second quarter ended March 29, 2014. The Company posted quarterly revenue of $45.6 billion and quarterly net profit of $10.2 billion... Read more
Award-Winning NoteSuite Productivity App is $...
Minneapolis based Theory.io has announced an 80-Percent Markdown NoteSuite for iPad. NoteSuite helps users stay organized by capturing their notes, to-dos and documents in one organized place.... Read more
16GB 1st generation iPad mini available for $...
Radio Shack has a select number of refurbished 1st generation 16GB WiFi iPad minis available for $199.99 on their online store. Choose free shipping or free ship-to-store. We expect these to sell out... Read more
13-inch 2.5GHz MacBook Pro on sale for $100 o...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $1099 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
iPad Sales “Lull” A Reality Correction Of Unm...
I have lots of time for Jean-Louis Gassée, the former Apple Computer executive (1981 to 1990) who succeeded Steve Jobs as head of Macintosh development when the latter was dismissed in 1985. Mr.... Read more
Apple Makes OS X Betas Available To All – Wit...
Apple’s OS X Beta Seed Program, which lets you install the latest pre-release builds, try it out, and submit your feedback, is now open to anyone who wants to sign on rather than to developers and... Read more
Apple Releases iOS 7.1.1 Update
The latest iOS 7.1.1 update contains improvements, bug fixes and security updates, including: • Further improvements to Touch ID fingerprint recognition • Fixes a bug that could impact keyboard... Read more
Logitech Announces Thinner, Lighter, More Fle...
Logitech has announced an update to its Ultrathin for iPad Air, iPad mini and iPad mini with Retina display, improving the flexibility and design of its award-winning predecessor with an even thinner... Read more
Logitech Introduces Hinge, Big Bang and Turna...
Logitech has announced expansion of its tablet product line with three new cases – the Logitech Hinge, the Logitech Big Bang and the Logitech Turnaround – each for the iPad Air, iPad mini and iPad... Read more
WaterField’s Rough Rider Leather Messenger Ba...
WaterField Designs have announced the new 15-inch size of their popular Rough Rider leather messenger bag, a vintage-looking bag that combines Old West charm and ruggedness with distinctly modern... 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) - 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
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
*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* Inc. Research Data Specialist - Appl...
…of Worldwide Market Research & Intelligence. The team is responsible for conducting Apple branded consumer market research. It is also responsible for analyzing data Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.