There&#39;s no `eth0` on default configuration of OS X. By default, `en0` and `en1` are your physical network connections (wired and wireless LAN). `lo0` is the loopback interface. `fw0` is the IP over Firewire interface; and `vmnet` interfaces are installed by VMware for network communication with virtual machines.

`en0` and `en1` are your physical wired/wireless cards.

`lo0` is the loopback device, which is used for entirely internal communication, ie. between two applications both running on your PC.

`fw0` is for networking over firewire I believe.

`vment*` - is used by VMWare Fusion to provide networking to your virtual machines, and there&#39;s likely to be one per VM you have set up.

I have a defined fixed width and height to resize an image. However, I have problem a with this, because the image can have any kind of size ratio (it can be **vertical** or the **horizontal**). In this case, fixed width and height cause a problem. I want to calculate **width and height** in a smarter way.

For example lets say I have defined **width 1024px and height 768px**. And I want to resize an image which is vertical **(height 1100px and width 200px)**. So in my case it will resize to fixed **size (1024x768)**, so the width will be increased from **100px to 768px**, and it will be very ugly. Similarly if the image has height less than **768px**, it will increase the height by force to **768px**.

Therefore I would like to calculate the new image size based on the original image size ratio. Lets say if the above example image should be resized to maximum height of **768px**, but then what about the width? it&#39;s already less than my &quot;maximum width&quot;, which is **200px**, so should the width remain unchanged? or should it be further decreased?

Similarly, if the image has **the height 200px, and the width 1100px**. So the width should be **decreased to 1024px**, but what about the height?

The third problem is that, let&#39;s suppose if both height and width are more than the maximum height and maximum width, let&#39;s say **width: 1100px and height:4000px**. Now since width and height both are more than the maximum width and maximum height but the image is vertical, it will make it horizontal. So how can I check if in this case if I should resize the image according to maximum height, or according to maximum width?

I appreciate any help with this.

Calculating image size ratio for resizing

In a bash script, I need to determine whether an executable named `foo` is on the PATH.

Detect if executable file is on user&#39;s PATH

just a question for my understanding. on my mac when I use `ifconfig` command on my mac I get the following interfaces:

 - en0
 - en1
 - lo0
 - fw0
 - vment0
 - vment1

I don&#39;t understand why there are so many. I understand that eth0 would be for LAN connections, and that en0 is the wireless connection. But macbook only has one airport..so why en1 as well? not sure what vments are for either. 

ifconfig and interfaces

<p>just a question for my understanding. on my mac when I use <code>ifconfig</code> command on my mac I get the following interfaces:</p>
<ul>
<li>en0</li>
<li>en1</li>
<li>lo0</li>
<li>fw0</li>
<li>vment0</li>
<li>vment1</li>
</ul>
<p>I don't understand why there are so many. I understand that eth0 would be for LAN connections, and that en0 is the wireless connection. But macbook only has one airport..so why en1 as well? not sure what vments are for either.</p>


I am a complete newbie at Mac. It so happened that now I&#39;m working on it. I have an weird issue - I can&#39;t find how to start default Color Picker?

How to start color picker on Mac OS?

I&#39;ve instaled the Java for Developer package provided from Apple for 10.7 and java apps are running fine

but eclipse cannot find the JDK root path and I cant either.

Anybody any ideas?

JDK on OSX 10.7 Lion

I am using the Xcode beta for developers, and am noticing some subtle differences. Among them is a new attribute for declared properties.

    @property(strong)IBOutlet NSArrayController *arrayControl;

My question is: what does the strong attribute mean?? Does it replace some older one, or is it something entirely new? I have searched through google and the developer documentation and havent been able to find anything. Until i know what it is i am hesitant to use it.

Thanks in advance

What is the strong property attribute

I am trying to access a `model.filefield` in Django to parse a [CSV][1] file in Python using the `csv` module. It&#39;s working on Windows, but on Mac it gave me this:

    Exception Type: Error

    Exception Value: new-line character seen in unquoted field - do you need to open the file in universal-newline mode?

This is the code:

    myfile = customerbulk.objects.all()[0].fileup

    mydata = csv.reader(myfile)
        for email,mobile,name,civilid in mydata:
            print email,mobile,name,civilid

  [1]: http://en.wikipedia.org/wiki/Comma-separated_values


Open the file in universal-newline mode using the CSV Django module

I am going to set the path for mySQl on my computer (I&#39;m running Snow Leopard) but I see different instructions online.

Some say to change the .profile file and some say to change the .bash_profile file. What is the difference?

Difference between .profile and .bash_profile on Snow Leopard

I have a class and an interface, and when I try to instantiate the interface, I get an error:

&gt; Cannot create an instance of the abstract class or interface

My code is below:


    namespace MyNamespace
    {
        public interface IUser
        {
            int Property1 { get; set; }
            string Property2 { get; set; }
            string Property3 { get; set; }
            void GetUser();
        }
    
        public class User : IUser
        {
            public int Property1 { get; set; }
            public string Property2 { get; set; }
            public string Property3 { get; set; }
            
            public void GetUser()
            {
               //some logic here...... 
            }
    
        }
    }

When I try to instantiate `IUser user = new IUser();` I get an error:

&gt; Cannot create an instance of the abstract class or interface


What am I doing wrong here?








Why do I get an error instantiating an interface?

What is the best way to write junit tests for interfaces so they can be used for the concrete implementing classes?

e.g. You have this interface and implementing classes:

    public interface MyInterface {
        /** Return the given value. */
        public boolean myMethod(boolean retVal);
    }
    
    public class MyClass1 implements MyInterface {
        public boolean myMethod(boolean retVal) {
            return retVal;
        }
    }
    
    public class MyClass2 implements MyInterface {
        public boolean myMethod(boolean retVal) {
            return retVal;
        }
    }

How would you write a test against the interface so you can use it for the class?

Possibility 1:

    public abstract class MyInterfaceTest {
        public abstract MyInterface createInstance();
        
        @Test
        public final void testMyMethod_True() {
            MyInterface instance = createInstance();
            assertTrue(instance.myMethod(true));
        }

        @Test
        public final void testMyMethod_False() {
            MyInterface instance = createInstance();
            assertFalse(instance.myMethod(false));
        }
    }
    
    public class MyClass1Test extends MyInterfaceTest {
        public MyInterface createInstance() {
            return new MyClass1();
        }
    }
    
    public class MyClass2Test extends MyInterfaceTest {
        public MyInterface createInstance() {
            return new MyClass2();
        }
    }

Pro:

 - Need only one method to be implemented

Con:

 - Dependencies and mock objects of class under test have to be the same for all tests

Possibility 2:

    public abstract class MyInterfaceTest
        public void testMyMethod_True(MyInterface instance) {
            assertTrue(instance.myMethod(true));
        }

        public void testMyMethod_False(MyInterface instance) {
            assertFalse(instance.myMethod(false));
        }
    }
    
    public class MyClass1Test extends MyInterfaceTest {
        @Test
        public void testMyMethod_True() {
            MyClass1 instance = new MyClass1();
            super.testMyMethod_True(instance);
        }
        
        @Test
        public void testMyMethod_False() {
            MyClass1 instance = new MyClass1();
            super.testMyMethod_False(instance);
        }
    }
    
    public class MyClass2Test extends MyInterfaceTest {
        @Test
        public void testMyMethod_True() {
            MyClass1 instance = new MyClass2();
            super.testMyMethod_True(instance);
        }
        
        @Test
        public void testMyMethod_False() {
            MyClass1 instance = new MyClass2();
            super.testMyMethod_False(instance);
        }
    }

Pro:

 - fine granualtion for each test including dependencies and mock objects

Con:

 - Each implementing test class requires to write additional test methods

Which possibility would you prefer or what other way do you use?

How to write junit tests for interfaces?

The reason for interfaces truly eludes me. From what I understand, it is kind of a work around for the non-existent multi-inheritance which doesn&#39;t exist in C# (or so I was told).

All I see is, you predefine some members and functions, which then have to be re-defined in the class again. Thus making the interface redundant. It just feels like syntactic… well, junk to me (Please no offense meant. Junk as in useless stuff).

In the example given below taken from a different C# interfaces thread on stack overflow, I would just create a base class called Pizza instead of an interface.

easy example (taken from a different stack overflow contribution)

    public interface IPizza
    {
        public void Order();
    }

    public class PepperoniPizza : IPizza
    {
        public void Order()
        {
            //Order Pepperoni pizza
        }
    }

    public class HawaiiPizza : IPizza
    {
        public void Order()
        {
            //Order HawaiiPizza
        }
    }


Interfaces — What&#39;s the point?

While I am learning Haskell, I noticed its **type class**, which is supposed to be a great invention that originated from Haskell.

However, in [the Wikipedia page on type class][1]:

&gt; The programmer defines a type class by specifying a set of function or
&gt; constant names, together with their respective types, that must exist
&gt; for every type that belongs to the class.

Which seems rather close to **Java&#39;s Interface** to me (quoting [Wikipedia&#39;s Interface(Java) page][2]):

&gt; An interface in the Java programming language is an abstract type that
&gt; is used to specify an interface (in the generic sense of the term)
&gt; that classes must implement.

These two looks rather similar: type class limit a type&#39;s behavior, while interface limit a class&#39; behavior.

I wonder what are the differences and similarities between type class in Haskell and interface in Java, or maybe they are fundamentally different?

**EDIT:** I noticed [even haskell.org admits that they are similar][3]. If they are so similar (or are they?), then why type class is treated with such hype?

**MORE EDIT:** Wow, so many great answers! I guess I&#39;ll have to let the community decide which is the best one. However, while reading the answers, all of them seem to just say that *&quot;there are many things typeclass can do while interface cannot or have to cope with generics&quot;*. I cannot help but wondering, are there anything **interfaces can do while typeclasses cannot?** Also, I noticed that Wikipedia claims that typeclass was originally invented in the 1989 paper *&quot;How to make ad-hoc polymorphism less ad hoc&quot;, while Haskell is still in its cradle, while Java project was started in 1991 and first released in 1995. So **maybe instead of typeclass being similar to interfaces, its the other way around, that interfaces were influenced by typeclass?** Are there any documents/papers support or disprove this? Thanks for all the answers, they are all very enlightening!

Thanks for all the inputs!


  [1]: http://en.wikipedia.org/wiki/Type_class
  [2]: http://en.wikipedia.org/wiki/Interface_%28Java%29
  [3]: http://www.haskell.org/haskellwiki/OOP_vs_type_classes#Type_classes_are_like_interfaces.2Fabstract_classes.2C_not_classes_itself

Java&#39;s Interface and Haskell&#39;s type class: differences and similarities?

Consider an example (which compiles in java)

    public abstract interface Interface {
    	public void interfacing();
    	public abstract boolean interfacing(boolean really);
    }

Why is it necessary for an interface to be &quot;declared&quot; abstract? Is there other rules that applies with an abstract interface?


----------
Finally: If `abstract` is obsolete, why is it included in Java? Is there a history for abstract interface?

Java abstract interface

How can I determine the IP address of a given request from within a controller? For example (in express):

    app.post(&#39;/get/ip/address&#39;, function (req, res) {
        // need access to IP address here
    })

How to determine a user&#39;s IP address in node

I am trying to develop a system where there are different nodes that are run on different system or on different ports on the same system. 

Now all the nodes create a Socket with a target IP as the IP of a special node known as a bootstrapping node. The nodes then create their own `ServerSocket` and start listening for connections. 

The bootstrapping node maintains a list of Nodes and returns them on being queried.

Now what I need is the node must register its IP to the bootstrapping node. I tried using `cli.getInetAddress()` once the client connects to the `ServerSocket` of bootstrapping node but that didn&#39;t work.

 1. I need the client to register its PPP IP if available;
 2. Otherwise the LAN IP if available; 
 3. Otherwise it must register 127.0.0.1 assuming its the same computer.

Using the code:

    System.out.println(Inet4Address.getLocalHost().getHostAddress());

or

    System.out.println(InetAddress.getLocalHost().getHostAddress());

My PPP Connection IP address is: 117.204.44.192 but the above returns me 192.168.1.2

**EDIT**

I am using the following code:

    Enumeration e = NetworkInterface.getNetworkInterfaces();
    while(e.hasMoreElements())
    {
        NetworkInterface n = (NetworkInterface) e.nextElement();
        Enumeration ee = n.getInetAddresses();
        while (ee.hasMoreElements())
        {
            InetAddress i = (InetAddress) ee.nextElement();
            System.out.println(i.getHostAddress());
        }
    }

I am able to get all the IP addresses associated all `NetworkInterface`s, but how do I distinguish them? This is the output I am getting:

    127.0.0.1
    192.168.1.2
    192.168.56.1
    117.204.44.19

Getting the IP address of the current machine using Java

Is there a way to figure out the country name just by looking at an IP address? I mean, do countries have specific ranges of IP addresses? For example, Australia can have IP addresses only in the range of `123.45.56.89 - 231.54.65.98` (just an example)

Identifying country by IP address

I&#39;ve heard it&#39;s meant to be a security feature, but it often seems like a security problem. If I want to write a server that uses a privileged port, not only do I have to worry about how secure my code is, I have to especially worry about whether I&#39;m using `setuid` right and dropping privileges.

Why are ports below 1024 privileged?

I am writing unit tests for a client library. I want to test connecting with an invalid port and an invalid ip. What is a good ip address to use that won&#39;t potentially be routed somewhere? I don&#39;t want to make any assumptions about the network the machine running the unit tests is on. LOCALHOST seems like a bad choice since that is the valid machine running the server component and I want to test an invalid port separately. Is there an INVALID-IP reserved somewhere in the IPv4 spec?

what is a good invalid IP address to use for unit tests?

I need to retrieve the default gateway on a Mac machine. I know that in Linux route -n will give an output from which I can easily retrieve this information. However this is not working in Mac OSX(Snow Leopard). 

I also tried `netstat -nr | grep &#39;default&#39;`, but I was hoping for a cleaner output like that produced by `route -n` in Linux/Unix. `netstat -nr` lists all the interfaces and the default gateway for them.

Any kind of suggestion or a hint in the right direction will be appreciated.

How to get default gateway in Mac OSX

I am looking for a command line solution that would return me the primary (first) IP address of the localhost, other than 127.0.0.1

The solution should work at least for Linux (Debian and RedHat) and OS X 10.7+

I am aware that `ifconfig` is available on both but its output is not so consistent between these platforms.

How to get the primary IP address of the local machine on Linux and OS X?

`ip link` shows this:

    [root@0-25-90-68-79-4a log]# ip link
    1: lo: &lt;LOOPBACK,UP,LOWER_UP&gt; mtu 65536 qdisc noqueue state UNKNOWN 
        link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    2: eth0: &lt;BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP&gt; mtu 1500 qdisc mq master bond0 state UP qlen 1000
        link/ether 00:25:90:68:79:4a brd ff:ff:ff:ff:ff:ff
    5: bond0: &lt;BROADCAST,MULTICAST,MASTER,UP,LOWER_UP&gt; mtu 1500 qdisc noqueue state UP 
        link/ether 00:25:90:68:79:4a brd ff:ff:ff:ff:ff:ff
    8: gre0: &lt;NOARP&gt; mtu 1476 qdisc noop state DOWN 
        link/gre 0.0.0.0 brd 0.0.0.0
    10: 35978f0: &lt;BROADCAST,MULTICAST,UP,LOWER_UP&gt; mtu 1500 qdisc pfifo_fast master br35978f0 state UP qlen 32
        link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
    13: br35978f0: &lt;BROADCAST,MULTICAST,UP,LOWER_UP&gt; mtu 1500 qdisc noqueue state UP 
        link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff

Here, the interface **35978f0** is the virtual interface which is tied to the bridge **br 35978f0**. I&#39;ve already done `ifconfig 35978f0 down` and `brctl delif br35978f0 35978f0`.

But how do I delete interface **35978f0**?


How do I delete virtual interface in Linux?

I&#39;ve just installed ubuntu docker image, when I execute &quot;ifconfig&quot; it says there&#39;s no such command, I tried apt-get install by there&#39;s no package named &quot;ifconfig&quot;(I can install some other images).

So how to do this?
Thanks.

Content Type	Original Author	Original Content on Stackoverflow
Question	lollercoaster	View Question on Stackoverflow
Solution 1 - Macos	mmx	View Answer on Stackoverflow
Solution 2 - Macos	Matthew Scharley	View Answer on Stackoverflow

ifconfig and interfaces

Macos Problem Overview

Macos Solutions

Solution 1 - Macos

Solution 2 - Macos

Detect if executable file is on user's PATH

Calculating image size ratio for resizing

Attributions