I am very much new to regex and I need to create one to parse logs into a shorter subset of that log message.   For instance, I have the log:  System trap received SystemString=Mon Jan 07 15:36:07 2017. System 1464333684: Type: Timing Quality le-5 System, Class: Timing, Level: None, Action: Clear System, Flags: 0x15   And I would like to parse and retrieve from it:   Timing Quality le-5 System, Class: Timing   At first this looked really trivial to me, but after watching many tutorials on regex... I am confused on how to approach such a task. Where do I begin?   Thanks in advance.
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?
How to find the mime type of a file in python? Showing a Sequence and its Limit are Closed Let $(X, d)$ be a metric space, and $(x_n)_{n \in \mathbb{N}}$ a sequence in $X$, with $x_n \rightarrow x$ w.r.t. $d$ for some $x \in X$. Show that the set $\{x_n : n \in \mathbb{N}\}\cup\{x\}$ is closed in $(X, d)$.   I figured I should use $\overline{F} = F \cup F'$ to show the above set is closed. Let $(x_n)_{n \in \mathbb{N}} = F$. Then, all elements of the sequence are in  $F$, which is equal to $\{x_n : n \in \mathbb{N}\}$. Clearly, the sequence (or $F$) has only one accumulation point, $x$. So, $F' = \{x\}$. This shows $\{x_n : n \in \mathbb{N}\}\cup\{x\} = \overline{F}$, and thus is closed.  Is this sufficient in proving the problem? Or would I have to show that $x$ is the only accumulation point as well (figured I don't have to because we know limits are unique)? Any advice would be very helpful. Thank you. Two  have been announced in LoL.  They have an ability that makes them be able to recall together.                                  What are the limits to this ability? Can the 'non-recaller' jump in at the last second and get some kind of instant recall?  Can somebody with the setup to get on PBE test it and tell us what are the limitations of this ability? iPhone 6s with iOS 12.4 not connecting to MacBook Pro mid2015 with macOS 10.14.6 When using the Text Editor, what is the best command to include inside a script which will abort the script at that line?  quit() and sys.exit() stop the script, but also kill Blender. I've been writing C and C++ code for almost twenty years, but there's one aspect of these languages that I've never really understood. I've obviously used regular casts i.e.  MyClass *m = (MyClass *)ptr;   all over the place, but there seem to be two other types of casts, and I don't know the difference. What's the difference between the following lines of code?  MyClass *m = (MyClass *)ptr; MyClass *m = static_cast&lt;MyClass *&gt;(ptr); MyClass *m = dynamic_cast&lt;MyClass *&gt;(ptr); How to find the sum $$\sum^n_{k=1} (k^2+k+1)k!$$  What I tried as follows :   $$\sum^n_{k=1} (k^2+k+1)k!$$  =$$\sum^n_{k=1} (k^2)k!+ \sum^n_{k=1} (k)k! + \sum^n_{k=1} (1)k!$$  Now we can write $\sum^n_{k=1} (k^2) $ as $$\frac{n(n+1)(2n+1)}{6}$$ but what to do with $k!$ please guide thanks....... How do "Dummy Variables" work? I do not understand how dummy variables work in math.   Suppose we have:  $$I_1 = \int_{0}^{\infty} e^{-x^2} dx$$  How is this equivalent to:  $$I_2 = \int_{0}^{\infty} e^{-y^2} dy$$  How does this dummy variable system work?   Since $y$ is the dependent variable for $I_1$ How can $y$ itself be and independent variable for $I_2$  ??  Thanks! What is the best way to restrict access to adult content? I bought my kids a PC and installed 12.04 (Unity) on it.  The bottom line is, I want my children to use the computer unsupervised while I have confidence they cannot access anything inappropriate.  What I have looked at:  I was looking at Scrubit a tool which allows me configure my wifi router to block content and this solution would also protect my other PC and mobile devices.  This may be overkill as I just want the solution to work on one PC.    I also did some Google searches and came across the application called .  My experience of OSS is that the best solutions frequently never appear first on a Google search list and in this case I need to trust the methods therefore my question is very specific.   I want to leverage your knowledge and experience to understand What is the best way to restrict adult content on 12.04 LTS as this is important to me.  It maybe a combination of things so please don't answer this question "try this or that", then give me some PPA unless you can share your experience of how good it is and of course if there are any constraints. Is cancer caused by vitamin B17 deficiency? Proof of the L'Hôpital Rule for $\frac{\infty}{\infty}$ I ask for the proof of the L'Hôpital rule for the indeterminate form $\frac{\infty}{\infty}$ utilizing the rule for the form $\frac{0}{0}$.   Theorem: Let $f,g:(a,b)\to \mathbb{R}$ be two differentiable functions such as that:  $\forall x\in(a,b)\ \ g(x)\neq 0\text{ and }g^{\prime}(x)\neq 0$ and $\lim_{x\to a^+}f(x)=\lim_{x\to a^+}g(x)=+\infty$ If the limit $$\lim_{x\to a^+}\frac{f^{\prime}(x)}{g^{\prime}(x)}$$ exists and is finite, then  $$\lim_{x\to a^+}\frac{f(x)}{g(x)}=\lim_{x\to a^+}\frac{f^{\prime}(x)}{g^{\prime}(x)}$$  My attempt:  Since $\lim_{x\to a^+}f(x)=+\infty$, $$\exists \delta&gt;0:a&lt;x&lt;a+\delta&lt;b\Rightarrow f(x)&gt;0\Rightarrow f(x)\neq 0$$  Let $F,G:(a,a+\delta)\to \mathbb{R}$, $F(x)=\frac{1}{f(x)}$, $G(x)=\frac{1}{g(x)}$. Then by the hypothesis $\lim_{x\to a^+}F(x)=\lim_{x\to a^+}G(x)=0$, $$\forall x\in(a,b)\ \ G(x)\neq 0\text{ and }G^{\prime}(x)=-\frac{1}{g^2(x)}g^{\prime}(x)\neq 0$$ The question is, does the limit $$\lim_{x\to a^+}\frac{F^{\prime}(x)}{G^{\prime}(x)}=\lim_{x\to a^+}\frac{-\frac{1}{f^2(x)}f^{\prime}(x)}{-\frac{1}{g^2(x)}g^{\prime}(X)}=\lim_{x\to a^+}\frac{g^2(x)f^{\prime}(x)}{f^2(x)g^{\prime}(x)}$$ exist?   The limit $$\lim_{x\to a^+}\frac{f^{\prime}(x)}{g^{\prime}(x)}$$ exists by the hypothesis but we don't know if the limit $\displaystyle\lim_{x\to a^+}\frac{g^2(x)}{f^2(x)}$ exists to deduce that the limit $$\lim_{x\to a^+}\frac{F^{\prime}(x)}{G^{\prime}(x)}$$ exists to use the L'Hôpital Rule for the form $\frac{0}{0}$.  EDIT: After discussing it with other users in the site, we came to the conclusion that this proof is only partial and can't logically be continued to yield the Theorem.  As a result, the rule for the $\frac{0}{0}$ form can't be used to proove the rule for the  $\frac{\infty}{\infty}$ form. Mr. Tavares and myself have already given two different proofs (with the pretty much the same main idea) of the Theorem in question using Cauchy's Mean Value Theorem. You can read them below. You can also read the proof Rudin gives for a stronger version of the Theorem (that does not suppose that $\lim_{x\to a^+}f(x)=+\infty$) in his book Principle of Meathematical Analysis. If you have any objections in either proofs please let me know. Thank you. If $f$ is bounded and $\lim_{x \to c} g(x) = 0$, then $\lim_{x \to c}g(x)f(x) = 0$ It seems as if a shift occurred and the descriptive "Oriental" was replaced by "Asian" as the accepted term in polite society — what caused this shift? Example of the equality of an inequality This question is related to Daniel Fischer's answer . Suppose $f$ is a real $C^{1}$ function on $[0, 1]$ such that $f(0) = 0$ and $\int_{0}^{1}f'(x)^{2}\, dx \leq 1$. Then (essentially by Cauchy-Schwarz), we have $\left|\int_{0}^{1}f(x)\, dx\right| \leq 2/3$ as Daniel Fischer stated in his answer.  My question is: Is there an example of a function such that we have equality in $\left|\int_{0}^{1}f(x)\, dx\right| \leq 2/3$? I was thinking of maybe a smoothed version of a function which takes the value $0$ on $[0, 1/2)$ and $4/3$ on $(1/2, 1]$ but that seems complicated to construct, moreover, the derivative in some neighbourhood of $1/2$ might be hard to control. What is crop factor and how does it relate to focal length? $a^m=b^m$ and $a^n=b^n$ imply $a=b$ Let $D$ be an integral domain and let $a^m=b^m$ and $a^n=b^n$ where $m$ and $n$ are relatively prime integers, $a,b \in D$.   How do I show $a=b$? outline object effect How can I achieve an outline effect similar to the ones found in League of Legends or Diablo III?      Is it done using a shader? How? I would prefer answers that are not tied up to any particular engine but one that I can adapt to whatever engine I'm working on. Dispatcher.BeginInvoke: Cannot convert lambda to System.Delegate Pointer to class data member "::*" What are your thoughts on epigraphs in theses? I am wondering if there is a general consensus as to the suitability of epigraphs in a thesis, either a single one at the start of the document, or an appropriate quote to begin every chapter.  For example, at the start of a technical chapter describing some code, I could write     Beware of bugs in the above code; I have only proved it correct, not tried it. - Donald E. Knuth   I am lucky to have complete freedom over how I choose to typeset my thesis (Master's thesis in astronomy) and I like the idea of a thematic quote to begin a chapter. However, I am wary of seeming unprofessional or tacky so I am curious to get some more thoughts on the matter.