I am new to regex and i want to extract strings from file path. Below is the mentioned filepath from which i want to extract string:  input : c://dev-dl-data-d2-us=east-1-5148727/all/stage/clinical/cro/raw/c/ca209_040/2018/08/02/aesae.csv  Output: ca209_040,aesae.csv
I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?
Prove that the product of a non-zero rational and irrational number is irrational. Could you please confirm if this proof is correct?  Theorem: If $q \neq 0$ is rational and $y$ is irrational, then $qy$ is irrational.  Proof: Proof by contradiction, we assume that $qy$ is rational. Therefore $qy=\frac{a}{b}$ for integers $a$, $b \neq 0$. Since $q$ is rational, we have $\frac{x}{z}y=\frac{a}{b}$ for integers $x \neq 0$, $z \neq 0$. Therefore, $xy = a$, and $y=\frac{a}{x}$. Since both $a$ and $x$ are integers, $y$ is rational, leading to a contradiction. On what criteria should I evaluate domain registrars? Though I've been a web developer for a fair amount of time, I am going for the first time to buy a few domain names.  I have looked into the domains I'm going to buy and know that they're available, and I've been looking into which sellers to use.  After doing a lot of research, the main ones I'm considering are 1&amp;1, Namecheap, and Gandi.  The problem is, when continuing to research, I'm not really sure what makes one domain seller distinct from another.  I don't need much in the way of services--definitely not hosting, since I plan to use Heroku for that.  I mainly only need the domain itself and DNS management, as well as possibly SSL certificates and WHOIS protection.  Question:  What makes one domain seller different from another?  How can I go about evaluating which one is the best for me?  Note:  This question is not which domain seller is the best, but rather, what criteria can I use to evaluate them and rank one over another.  I'm trying to find out what makes one domain seller different from another, since they all seem to be pretty similar to me right now. Interpreting plot.lm() I had a question about interpreting the graphs generated by plot(lm) in R.  I was wondering if you guys could tell me how to interpret the scale-location and leverage-residual plots?  Any comments would be appreciated.  Assume basic knowledge of statistics, regression and econometrics. .NET Attributes: Why does GetCustomAttributes() make a new attribute instance every time? Replaced wrong car in garage in GTA Online Inconsistent behavior when typing a number into the search field Are there any rulesets or laws for Q or Q continuum? Anything, that would prevent them from doing... anything? Or at least limit them from doing something really bad?  In "" episode Q explains to  that they can do, have, get, become anything they want or appear anywhere they want, with just a snap of fingers. If that is true and if there are absolutely no borders or limits, they can't pass, then how can universe work in general? Or, how did it manage to exist so far?  I mean -- any Q could wipe out Borg, entire human population or even entire universe... with just a snap of fingers. What could prevent Q from doing that? Last night I took some night sky shots, and I've noticed that with long exposure times (15s, 30s) the time it took to store the images in the camera memory card (jpeg) took roughly as long?  The actual file size is fairly small at 1 to 3MB per file.  Any idea why this is? Do I use ext4 for all partitions (such as / and /boot)? What are the other formats used for? I'm installing ubuntu onto a new laptop with 24gb SSD and a 500gb HDD. I wanted to put / and swap onto the SSD and /home onto the HDD. Is there anything I shouldn't use ext4 for?  I do not ever intend to dual boot. Ubuntu only. Why $\lim\limits_{n\to \infty}\left(1+\frac{1}{n}\right)^n$ doesn't evaluate to 1? I am trying to identify what the flaw is exactly when reasoning about a limit such as the definition of $\mathbf e$:  $$ \lim_{n\rightarrow \infty}\left(1+\frac{1}{n}\right)^n={e} $$  Now, I know there are ways of proving this limit, such as by considering the binomial expansion of $(1+\frac{1}{n})^n$ and comparing that to the Maclaurin series of $e$. So to make this clear, I am not looking for a proof of the limit definition of $e$.  I tried searching for "limit laws/rules" but none of the rules I found described the above case. Hence, I am looking for a specific rule (or perhaps a certain perspective) that will help me realize why the above does not in fact evaluate to 1.  My train of thought is as follows: at a first glance, if I wasn't already familiar with what the limit evaluates to, I probably would evaluate the expression inside the brackets first, and then apply the limit to the power. So, $$\displaystyle\lim_{n\to\infty}\frac{1}{n}=0\quad\text{and then}$$  $$\displaystyle\lim_{n\rightarrow \infty}\left(1+0\right)^n=\lim_{n\to\infty}1^n=1$$  Why is my reasoning flawed? "...his parents' dream of *him* achieving a Cambridge degree." What is the function of "him" here? I have a problem analysing this sentence from the point of finite/nonfinite clauses, clause elements and their functions:     He does not want to destroy his parents' dream of him achieving a Cambridge degree.   I am especially interested in the: dream of him achieving a Cambridge degree.  I know that 'achieving a Cambridge degree' is a non-finite -ing participle clause. However what is its function? And what is the function of 'of him'? Is it a postmodification? #!/bin/bash  SUBJECT="WARNING CPU USAGE HIGH" TO=gmail id MESSAGE=/tmp/messages echo "#######################" &gt; $MESSAGE echo "CPU statistics as follows.." &gt;&gt; $MESSAGE mpstat &gt;&gt; $MESSAGE echo "#######################" &gt;&gt; $MESSAGE CPU_USAGE=$(top -b -n1 | awk '/^Cpu/ {print $2}' | cut -d. -f1) [ $CPU_USAGE -gt 85 ] &amp;&amp; mail -s "$SUBJECT" "$TO" &lt; $MESSAGE`   ./cpu.sh: line 11: [: -gt: unary operator expected What might be the reason What is the error "Every derived table must have its own alias" in MySQL? How do I get the linksys WUSB6300 wireless adapter to work on linux An example of a sequence of Riemann integrable functions $(f_n)$ that converges pointwise to a function $f$ that is not Riemann integrable. Choosing variables to include in a multiple linear regression model I am currently working to build a model using a multiple linear regression. After fiddling around with my model, I am unsure how to best determine which variables to keep and which to remove.  My model started with 10 predictors for the DV. When using all 10 predictors, four were considered significant. If I remove only some of the obviously-incorrect predictors, some of my predictors that were not initially significant become significant. Which leads me to my question: How does one go about determining which predictors to include in their model? It seemed to me you should run the model once with all predictors, remove those that are not significant, and then rerun. But if removing only some of those predictors makes others significant, I am left wondering if I am taking the wrong approach to all this.  I believe that  thread is similar to my question, but I am unsure I am interpreting the discussion correctly. Perhaps this is more of an experimental design topic, but maybe someone has some experience they can share. Reading the reviews of the  on Google Play,  said that since Chrome supports HTML5, he had managed to persuade the BBC iPlayer website to play him streams meant for iPad/iPhone devices by spoofing an IOS user agent string on his Nexus 7.  How might I go about getting the same thing to work myself?  I have looked at  and  but both seem to concentrate on the Dolphin browser. Also, please mention if a solution will require me to root my Nexus-7.  Incidentally, I also tried using  with Firefox, but although Firefox supports HTML5 and the iPlayer website shows pages without either install flash or use external app messages, it still won't play the streams (it just sits swirling its progress wheel), hence looking for a solution for Chrome. Why is "cupboard" pronounced with a silent "p"? Given this (very) tricky determinant, how can we calculate it easily?  $$\begin{pmatrix} \alpha + \beta &amp; \alpha \beta &amp; 0 &amp; ... &amp; ... &amp; 0 \\ 1 &amp; \alpha + \beta &amp;  \alpha \beta &amp; 0 &amp; ... &amp; 0 \\ 0 &amp; 1 &amp; \alpha + \beta &amp; \alpha \beta &amp; ... &amp; ... \\ ... &amp; ... &amp; ... &amp; ... &amp; ... &amp; 0 \\ ... &amp; ... &amp; .... &amp; ... &amp; ... &amp; \alpha \beta \\ 0 &amp; 0 &amp; 0 &amp; ... &amp; 1 &amp; \alpha + \beta   \\ \end{pmatrix} \in M_{n\times n}$$  EDIT:     I have to prove it is equal to $\frac{{\alpha}^{n+1} - {\beta}^{n+1}}{\alpha - \beta}$   Any help is appreciated, I just could not find a trick to ease it up! I'm Egyptian and flying to Cairo from Tbilisi, via Istanbul. The first flight Tbilisi-Istanbul is on Atlasjet, then from Istanbul to Cairo I am flying on Egyptair. For that, I have to recheck in at Istanbul to my Egyptair flight  Will I need to pass passport control at Istanbul airport to collect my bags and check in on Egyptair? Will I need a transit visa for that? Or it can be all done through neutral zone?