does apt-get checks cache directory before downloading packages
How can I install software or packages without Internet (offline)?
When I installed the latest update of Ubuntu, I was asked for the username but I do not remember what my username is. How do I find out what my username is? I accidentally unset all the directories of $PATH while trying to add a new one in ~/.bashrc. I opened a new terminal window as I was editing and now $PATH is empty. I'm worried if I boot from another drive to find the $PATH I won't be able to boot into this drive again.  Basically, what is the default result of echo $PATH? Create model from XYZ data points I'm trying to create a 3D heat map model out of data that I have from a csv file. I have a few thousand data points with XYZ coordinates.  I'm able to import the data into blender as a point cloud with , however I would like to create a model with solid faces. Is there a way when importing the data to somehow join the points to create faces instead of generating thousands of separate points?  Currently, this what I have in terms of point cloud  The end product would look something like this (minus the texture) and obviously the model wouldn't be as regular as this one  Any help is greatly appreciated! I am having some issues trying to show multiple fields for a single label in QGIS. In QGIS2.6, attempting to display labels for a feature consisting of multiple fields results in an empty label if one of the fields is null. So for example, in the label expression dialog:  concat("Temp Site",'\n',"Notes",'\n',"Function")   will function normally unless one of the fields is null, then it results in no label being shown. Using the '||' operator instead in the expression dialog also results in the same behaviour:  "Temp Site" || '\n'  ||  "Notes" || '\n'  ||  "Function"   Is there a way to display the labels even if one of the fields is null? Is the size of a Form in Visual Studio designer limited to screen resolution? Where can I find free elevation data for Europe?   The available resolutions and terms of use are important details that I also seek. Printing an array to a file with each element of the array in a new line in bash I am trying very hard to install Canon LBP2900b Printer in Ubuntu 13.10.  I have searched and googled a lot for the solution over fortnight but none of the site / link gave me the simple solution for me. How can accomplish my goal? Connecting multiple screens to the 2016 MacBook Pro with Touch Bar I'm thinking about buying the new MacBook Pro with 4 USB-C ports.  I want to attach two screens, mouse and keyboard and ethernet to the MacBook Pro while using the fewest number of USB-C ports possible.  So what I need is an adaptor with:   two DP or HDMI ports (or one DP port with daisy chaining support) two or more USB ports an ethernet port   Best case would be a hub to which all devices are connected with a single connection to the MacBook Pro, including power supply. Worst case if attaching the MacBook Pro to the devices would require me to use all four of USB-C ports.  Given the answers up to far, I can tell that:   Daisy chaining might or might not work with the MacBook Pro (since it requires DP1.2 which is supported by the graphics chipset, but it's uncertain if it's supported by the MacBook Pro itself) I can attach the monitors with two cables as a last resort, leaving me with two ports for the remaining peripherals.   What I still don't know:   Would daisy chaining work with a hub or does it require the first monitor to be directly attached to the MacBook Pro? Does some kind of hub exist supporting attachment of all listed devices with a single upstream connection to the MacBook Pro? Simple Hadamard Circuit gives incorrect results? Unable to open Chrome WebDriver in another language I'd really like to write a Selenium WebDriver test that verifies text is localized. The localization code bases the strings it displays on navigator.language (or navigator.userLanguage for IE). I cannot figure out, however, how to launch a Chromium window for a different language.  I see this bug which sort of explains the problem (closed as not a bug):   Here's how I create the browser instance:  var webdriver = require('selenium-webdriver'); var chrome = require("selenium-webdriver/chrome");  var options = new chrome.Options(); options.addArguments('--lang=es'); var caps = options.toCapabilities(); var driver = webdriver.Builder().withCapabilities(caps).build();   I installed the Spanish language, but whereas navigator.languages includes es in its list, but even if I move it to the top of the preferences, en-US is still what navigator.language is set to.  Have any of you found a way to successfully write multi-language tests with Selenium WebDriver? I have a COM dll written in vb6. When I try to create a new object of a class module from this dll I get a Run timer error 430: Class does not support automation or does not support expected interface. The interesting thing is that this happens only from outside the IDE, when I am debugging from within the IDE there is no error thrown and the new object of the class is created successfully. What can be the cause?  In general I occasionally get these kind of errors in COM dlls. What is the best way to debug COM issues? How can I know the path of the dll that is being used when a program is running? Realtek RTL8723be doesn't have good reception Only when I'm closer to the router, it shows any signal, but when I'm just little far from it, it is not showing wifi routers signals. Running junit tests in parallel in a Maven build? I'm using JUnit 4.4 and Maven and I have a large number of long-running integration tests.  When it comes to parallelizing test suites there are a few solutions that allow me to run each test method in a single test-class in parallel. But all of these require that I change the tests in one way or another.  I really think it would be a much cleaner solution to run X different test classes in X threads in parallel. I have hundreds of tests so I don't really care about threading individual test-classes.  Is there any way to do this? I am trying to write the Euclidean algorithm in the following way:  $A = \lfloor A \div B \rfloor \times B + (\text{remainder of}) \: A \div B $   Now is there any symbol I can use  to say "remainder of A $\div$ B"? I know that in the C programming language there is the operator % for modulus; is that a valid symbol in maths? Can I write A % B? Or is there some other way? Why is gradient the direction of steepest ascent? Changing Login Logo Is there a reason I would not add /usr/local/sbin, /usr/sbin, /sbin to my path on Debian? Let $V$ be spherically symmetric and $W$ i.i.d. Gaussian. Then $E[V|V+W=t]=g(\|t\|)$ A random vector $V \in \mathbb{R}^n$ is said to be spherically symmetric. If for every orthogonal matrix  $A$   the distribution of $AV$ is the same as the distribution of $V$.   My question: Let $W$ be  i.i.d. zero mean Gaussian random variable.     Can we show that  for a spherically symmetric $V$ the conditional expectation  \begin{align} E[V|V+W=t]=   g(\|t\|).  \end{align}  That is the conditional expectation is only a function of the magnitude.   My attempt:  \begin{align} E[V|V+W=t]= \int  V  \frac{f_W(t-v)}{f_{V+W}(t)} dP_V(v)= \frac{\int  v  f_W(t-v) dP_V(v)}{f_{V+W}(t)}= \frac{E[ V  f_W(t-V) ]}{f_{V+W}(t)} \end{align}  Therefore, we can show that the two functions in the above ratio only depend on $\|t\|$.   Observe that we can write $t= \|t\| u_t$  where $u_t$ is a unit vector. Then, for any orthogonal matrix $A$ \begin{align} f_{V+W}(t)=f_{V+W}(\|t\|, u_t)&amp;= \frac{1}{(2\pi)^{n/2}} E[ e^{-\frac{\|t-V  \|^2}{2}} ]\\ &amp;= \frac{1}{(2\pi)^{n/2}} E[ e^{-\frac{\|t-AV  \|^2}{2}} ]\\ &amp;= \frac{1}{(2\pi)^{n/2}} E[ e^{-\frac{\|tA^{-1}-V  \|^2}{2}} ]\\ &amp;= \frac{1}{(2\pi)^{n/2}} E[ e^{-\frac{\|t A^T-V  \|^2}{2}} ]\\ &amp;= f_{V+W}(tA^T)\\ &amp;= f_{V+W}(\|t\|,  u_t A^T) \end{align}  Since, $A$ was arbitrary  we have that $f_{V+W}(t)=h(\|t\|)$(i.e., only depends on the magnitute).  Now I am not sure how to show that $E[ V  f_W(t-V) ]$ only depends on $\|t\|$? How is Cooper's age justified?