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
$102.50
Apple Inc.
+0.25
MSFT
$45.43
Microsoft Corpora
+0.55
GOOG
$571.60
Google Inc.
+2.40

MacTech Search:
Community Search:

Software Updates via MacUpdate

VueScan 9.4.41 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Cloud 3.0.0 - 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
LibreOffice 4.3.1.2 - Free Open Source o...
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
SlingPlayer Plugin 3.3.20.505 - Browser...
SlingPlayer is the screen interface software that works hand-in-hand with the hardware inside the Slingbox to make your TV viewing experience just like that at home. It features an array of... Read more
Get Lyrical 3.8 - Auto-magically adds ly...
Get Lyrical auto-magically add lyrics to songs in iTunes. You can choose either a selection of tracks, or the current track. Or turn on "Active Tagging" to get lyrics for songs as you play them.... Read more
Viber 4.2.2 - 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
Cocktail 7.6 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
LaunchBar 6.1 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... 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
BBEdit 10.5.12 - Powerful text and HTML...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more

Latest Forum Discussions

See All

Qube Kingdom – Tips, Tricks, Strategies,...
Qube Kingdom is a tower defense game from DeNA. You rally your troops – magicians, archers, knights, barbarians, and others – and fight against an evil menace looking to dominate your kingdom of tiny squares. Planning a war isn’t easy, so here are a... | Read more »
Qube Kingdom Review
Qube Kingdom Review By Nadia Oxford on August 29th, 2014 Our Rating: :: KIND OF A SQUARE KINGDOMUniversal App - Designed for iPhone and iPad Qube Kingdom has cute visuals, but it’s a pretty basic tower defense game at heart.   | Read more »
Fire in the Hole Review
Fire in the Hole Review By Rob Thomas on August 29th, 2014 Our Rating: :: WALK THE PLANKUniversal App - Designed for iPhone and iPad Seafoam’s Fire in the Hole looks like a bright, 8-bit throwback, but there’s not enough booty to... | Read more »
Alien Creeps TD is Now Available Worldwi...
Alien Creeps TD is Now Available Worldwide Posted by Ellis Spice on August 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Dodo Master Review
Dodo Master Review By Jordan Minor on August 29th, 2014 Our Rating: :: NEST EGGiPad Only App - Designed for the iPad Dodo Master is tough but fair, and that’s what makes it a joy to play.   | Read more »
Motorsport Manager Review
Motorsport Manager Review By Lee Hamlet on August 29th, 2014 Our Rating: :: MARVELOUS MANAGEMENTUniversal App - Designed for iPhone and iPad Despite its depth and sense of tactical freedom, Motorsport Manager is one of the most... | Read more »
Motorsport Manager – Beginner Tips, Tric...
The world of Motorsport management can be an unforgiving and merciless one, so to help with some of the stress that comes with running a successful race team, here are a few hints and tips to leave your opponents in the dust. | Read more »
CalPal Update Brings the App to 2.0, Add...
CalPal Update Brings the App to 2.0, Adds Lots of New Stuff Posted by Ellis Spice on August 29th, 2014 [ permalink ] | Read more »
Baseball Battle Review
Baseball Battle Review By Jennifer Allen on August 29th, 2014 Our Rating: :: SIMPLE HITTINGUniversal App - Designed for iPhone and iPad Simple and cute, Baseball Battle is a fairly fun baseball game for those looking for something... | Read more »
Checkmark 2.1 Update Released, and it’s...
Checkmark 2.1 Update Released, and it’s on Sale for a Limited Time Posted by Jessica Fisher on August 29th, 2014 [ permalink ] | Read more »

Price Scanner via MacPrices.net

Labor Day Weekend MacBook Pro sale; 15-inch m...
B&H Photo has the new 2014 15″ Retina MacBook Pros on sale for up to $125 off MSRP. Shipping is free, and B&H charges NY sales tax only. They’ll also include free copies of Parallels Desktop... Read more
Labor Day Weekend iPad mini sale; $50 to $100...
Best Buy has the iPad mini with Retina Display (WiFi models) on sale for $50 off MSRP on their online store for Labor Day Weekend. Choose free shipping or free local store pick up. Price is for... Read more
13-inch 1.4GHz MacBook Air on sale for $899,...
Adorama has the new 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. Read more
It’s Official: Apple Issues Invitations To Se...
Apple has issued one of its characteristically cryptic press invitations for a special event to be held at the Flint Center for the Performing Arts in hometown Cupertino on Sept. 9, 2014 at 10:00 am... Read more
Tablet Shipments To See First On-year Decline...
TrendForce analyst Caroline Chen notes that when the iPad launched in 2010, it was an instant hit and spurred a tablet PC revolution, with tablets so popular that that notebook PC sales stagnated and... Read more
SOBERLINK Releases Apple iOS Compatible Handh...
Cypress, California based SOBERLINK, Inc., creator of the first handheld Breathalyzer designed to improve recovery outcomes, continues to show prominence in the mobile alcohol monitoring space with... Read more
New 21″ 1.4GHz iMac on sale again for $999, s...
Best Buy has the new 21″ 1.4GHz iMac on sale for $999.99 on their online store. Their price is $100 off MSRP. Choose free shipping or free local store pick up. Price is for online orders only, in-... Read more
Smartphone Outlook Remains Strong for 2014, U...
According to a new mobile phone forecast from the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, more than 1.25 billion smartphones will be shipped worldwide in 2014,... Read more
Save up to $60 with Apple refurbished iPod to...
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
12-Inch MacBook Air Coming in 4Q14 or 2015 –...
Digitimes’ Aaron Lee and Joseph Tsai report that according to Taiwan-based upstream supply chain insiders, Apple plans to launch a thinner MacBook model either at year end 2014 or in 2015, and that... Read more

Jobs Board

*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
*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
*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
*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
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.