*nix commands (and functions?) have a number with them, like fsck(8), killall(1), etc.    What does the number mean?
So, for example, when I type man ls I see LS(1). But if I type man apachectl I see APACHECTL(8) and if I type man cd I end up with cd(n).  I'm wondering what the significance of the numbers in the parentheses are, if they have any.
Website display problem - across all browsers whenever I go to  or  the page loads like this:    How can I fix this? Is Java "pass-by-reference" or "pass-by-value"? I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation? Does one need to be affiliated with a university to publish papers? Assume you have already completed your undergrad and have been working for a number of years. Does one need to be part of a university or a learning institution to publish papers? I am currently developing an RPG game with a classic experience-points and levelup mechanic. The player kills monsters, gains experience points, levels up when they collect enough and become stronger.  How do I balance the amount of Exp points necessary for reaching each level and the amount of Exp awarded by each monster on each level? Got NODATA issue: 'NODATA' (does the network require authentication?) I can use my mobile broadband to access Internet with Firefox but when I want to install any package from terminal or make 'apt-get update' command I got the following error:  got 'NODATA' (does the network require authentication?)   apt-get update output:  Get:1 extras.ubuntu.com trusty InRelease [213 B] 98% [1 InRelease gpgv 213 B] [Connecting to archive.ubuntu.com] Splitting up /var/lib/apt/lists/partial/extras.ubuntu.com_ubuntu_dists_trusty_InRelease into data Ign extras.ubuntu.com trusty InRelease E: GPG error: extras.ubuntu.com trusty InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)    output of `cat /var/lib/apt/lists/partial/extras.ubuntu.com_ubuntu_dists_trusty_InRelease  &lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"&gt; &lt;html&gt; &lt;head&gt; &lt;title&gt;404&lt;/title&gt; &lt;meta http-equiv="Cache-Control" content="no-cache"/&gt; &lt;/head&gt; &lt;body&gt; &lt;p&gt; Not Found &lt;/p&gt; &lt;/body&gt; &lt;/html&gt;   output of wget:  wget -O - http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease  --2014-06-01 09:23:35--  http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease Resolving extras.ubuntu.com (extras.ubuntu.com)... 91.189.92.152 Connecting to extras.ubuntu.com (extras.ubuntu.com)|91.189.92.152|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 213 [text/html] Saving to: ‘STDOUT’   0% [                                       ] 0           --.-K/s              &lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"&gt; &lt;html&gt; &lt;head&gt; &lt;title&gt;404&lt;/title&gt; &lt;meta http-equiv="Cache-Control" content="no-cache"/&gt; &lt;/head&gt; &lt;body&gt; &lt;p&gt; Not Found  &lt;/p&gt; &lt;/body&gt; &lt;/html&gt; recursive statistics on file types in directory? I did a website scrape for a conversion project. I'd like to do some statistics on the types of files in there -- for instance, 400 .html files, 100 .gif, etc. What's an easy way to do this? It has to be recursive.   Edit: With the script that maxschelpzig posted, I'm having some problems due to the architecture of the site I've scraped. Some of the files are of the name *.php?blah=blah&amp;foo=bar with various arguments, so it counts them all as unique. So the solution needs to consider *.php* to be all of the same type, so to speak. How to use XMLHttpRequest to download an HTML page in the background and extract a text element from it? Why is Buoyant Force $V\rho g$? For a submerged object, buoyant force ($F_b$) is defined as:  $$F_b = V_{\text{submerged}} \times \rho \text{ (density)} \times g \text{ (gravitational constant)}$$   Conceptually, the buoyant force equation says that buoyant force exerted is equal to the weight of the volume of water a given object displaced. Why? I went online to   and found the following explanation, but it seems like non-sequitur to me:      Explanation: When an object is removed, the volume that the object occupied will fill with fluid. This volume of fluid must be supported by the pressure of the surrounding liquid since a fluid can not support itself. When no object is present, the net upward force on this volume of fluid must equal to its weight, i.e. the weight of the fluid displaced. When the object is present, this same upward force will act on the object. How to typeset the symbol “^” (caret/circumflex/hat) I installed ubuntu 16.04 LTS, but there is no ubuntu one software, not in ubuntu software center also..Though it is showing selected in unity tweak tool.How can I get it. Please reply. Proof that $\suṃ̣_{k=1}^{n}k {n \choose k}$ for $n \in \mathbb N$ is equal to $n2^{n-1}$.  As a hint I got that $k {n \choose k} = n {n-1\choose k-1} $.  I tried solving this by induction but, in the inductive step I'm not arriving to the correct result. Is there a way to turn option strict off for just a single line of code?    I'm doing some maintenance work and I need to "cheat" in just one place and I don't want to lower the standard for the entire file. If $ua = au$, where $u$ is a unit and $a$ is a nilpotent, show that $u+a$ is a unit.   I've been working on this problem for an hour that I tried to construct an element $x \in R$ such that $x(u+a) = 1 = (u+a)x$. After tried several elements and manipulated $ua = au$, I still couldn't find any clue. Can anybody give me a hint? I met this equation frequently in Guass-Newton optimizations. But I dont understand why the left and right side of the equation can be equal.  Lets say the Jacobian is $2$ by $2$   and Hessian is $$\begin{bmatrix}\frac{\partial^2f_1}{\partial^2 x_1 } &amp; \frac{\partial^2f_1}{\partial^2 x_2  } \\ \frac{\partial^2f_2}{\partial^2 x_1 } &amp; \frac{\partial^2f_2}{\partial^2 x_2  }\end{bmatrix}$$   But the right hand side of the equation is  $$J^TJ =\begin{bmatrix} \left( \frac{\partial f_1}{\partial x_1} \right)^2 + \left( \frac{\partial f_2}{\partial x_1} \right)^2  &amp;  \frac{\partial f_1}{\partial x_1}\frac{\partial f_1}{\partial x_2} +\frac{\partial f_2}{\partial x_1}\frac{\partial f_2}{\partial x_1}\\ \frac{\partial f_1}{\partial x_1}\frac{\partial f_1}{\partial x_2} +\frac{\partial f_2}{\partial x_1}\frac{\partial f_2}{\partial x_1} &amp;\left( \frac{\partial f_1}{\partial x_2} \right)^2 + \left( \frac{\partial f_2}{\partial x_2} \right)^2\end{bmatrix} $$  Why can these two be equal as presented in papers? How to automatically fetch missing dependencies when installing software from .deb? jQuery :first vs. .first() Getting polygon shapefile node coordinates and point order I am working on the following problem from group theory:     If $G$ is a group of order $2n$, show that the number of elements of $G$ of order $2$ is odd.   That is, for some integer $k$, there are $2k+1$ elements $a$ such that $a \in G,\;\; a*a = e$, where $e$ is the identity element of $G$. Testing AuraHandledExceptions? It seems like when I call getMessage on a thrown AuraHandledException, I see "Script-thrown Exception" instead of the message that I have set. Any idea why this may be happening?  Controller:       @AuraEnabled     public static Conversation__c makeConversation(String tonum, String objid)     {         if (tonum.length() != 10)             throw new AuraHandledException('ToNumber length invalid.');     }   TestController:  @isTest     static void testMakeConversationInvalidTo()     {         Boolean testPass = false;         String fromNumber = '1234567890';         String toNumber = '1';          List&lt;ConversationController.ConversationWrapper&gt; test =    ConversationController.getConversations();         System.assertEquals(0, test.size());         try {             ConversationController.makeConversation(toNumber, '0');         } catch (AuraHandledException e) {             System.debug(e.getMessage());             System.debug(e.getTypeName());             System.assert(e.getMessage().contains('ToNumber length invalid'));             testPass = true;         }     }   Return:  16:26:28:477 USER_DEBUG [320]|DEBUG|Script-thrown exception 16:26:28:477 USER_DEBUG [321]|DEBUG|System.AuraHandledException I am applying for a UK visa. Can I show 5 months worth of bank statements for the UK visa, or is 6 months a requirement, as its not mentioned on their website?  There are no appointment dates showing in April. Is there any time limit in which we have to book an appointment after paying the fee?