I learned from  that there's 2 ways to control privileged activities: setuid and capability. But when I'm playing around with ping on my machine, it seems that it can bypass these 2 mechanism. First, confirm that on my machine /usr/bin/ping has cap_net_raw capability and it use SOCK_RAW: $ ll /usr/bin/ping -rwxr-xr-x 1 root root 72K Jan 31  2020 /usr/bin/ping  $ getcap /usr/bin/ping /usr/bin/ping = cap_net_raw+ep  $ strace -e socket ping &lt;some-ip&gt; socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE) = 5  Copying the binary will drop the capability but it still works: $ cp /usr/bin/ping ~  $ ll ~/ping -rwxr-xr-x 1 user user 72K Nov  4 16:54 /home/user/ping  $ getcap ~/ping [empty result]  $ ~/ping &lt;some-ip&gt; [it works]  I'm using Ubuntu 20.04 and 5.4.0-52-generic.
As far as I know, ping needs to create a  (which needs either root access or cap_net_raw capabilities). From my understanding the trend these last years has been to remove  binaries and replaced them with . However when I look at the ping binary on my Fedora 32, it doesn't look to have any: $ ls -la $(which ping) -rwxr-xr-x. 1 root root 82960 May 18 10:26 /usr/bin/ping $ sudo getcap -v $(which ping) /usr/bin/ping $     Does ping need to open raw socket on fedora? Or is there another way to give it the permission to open a raw socket?
The question asks to prove that -  $$\frac {\sin x} {\cos 3x} + \frac {\sin 3x} {\cos 9x} + \frac {\sin 9x} {\cos 27x}  = \frac 12 (\tan 27x - \tan x) $$  I tried combining the first two or the last two fractions on the L.H.S to allow me to use the double angle formula and get $\sin 6x$ or $\sin 18x$ but that did not help at all.   I'm pretty sure that if I express everything in terms of $x$, the answer will ultimately appear but I'm also certain that there must be another simpler way. What are the best practices for battery longevity? How do you maximize the cycle count of your battery?  There seems to be a debate between:   Leave plugged in 24/7 but do a full cycle once a month Charge to ~100%, drain to ~10%, repeat.   NOTE: Taking your   Which method is better and why? How much of a difference does it really make?  Here are some of the better sources I've found about battery behavior so far. Even still I feel they don't conclusively answer the question above. See my elaborations below:           Elaborating on Option 1  Now IF Apple engineers were smart and optimized for AC draw when plugged in to not use up your charge cycles, then it seem logical to assume that you are using effectively none of your 1000 charge cycles while plugged in. If that's the case, it would seem that the LiPo drop from holding at 100% would be vastly outweighed by the fact you're not using any charge cycles.  However, this is a purely speculative assumption and I could find no evidence to either confirm or deny.  If this is NOT true, and the AC adapter only goes to charging the battery, then there would be no difference. Your battery would drain to 99%, then back up to 100%, then back down to 99%, etc. Those micro-charge cycles would add up at the same rate as 100% -> 0% -> 100%, and you would get no gain. In this case the negative effect of holding LiPo batteries at 100% would outweigh everything else.  Elaborating on Option 2  There are lots of good reasons why Option 2 is the way it is:   Because of known LiPo chemistry issues, holding a 100% charge for a long time causes the battery to degrade Apple specifically recommends not to leave it plugged in all the time  Draining a battery all the way to zero all the time is bad for the cell (Which is why ~10% is used) Heat is a killer, and when plugged in AND charging, you get extra heat that causes damage.   There are a couple reasons why I'm challenging Option 2:   It seems silly that the most intuitive use case for thousands of people that use their macs as primary computers is wrong. If the hypothesis in option 1 is true, you're just burning unnecessarily through your finite charge cycles. It's a pain to have to remember to keep plugging in and plugging out and be worried about whether or not your device is plugged in. $X_n\leq Y_n$ implies $\liminf X_n \leq \liminf Y_n$ and $\limsup X_n \leq \limsup Y_n$ Can anyone prove this question? I tried but I didn't get any I idea, so I hope someone can solve it.     Let $X_n\leq Y_n$ for each $n\in \Bbb N$. Show that $\liminf X_n \leq \liminf Y_n$ and $\limsup X_n \leq \limsup Y_n$.   Please prove this question - thanks.  The definition I have:     Let $X_n$ be a sequence in real number and let $$E=\{x\in \Bbb R^\sharp:(X_{n_k}) \rightarrow x \text{ for some subsequence }(X_{n_k})\text{ of }(X_n)\}$$ for all $n \in \Bbb N$ and $k$ from $1$ to $\infty$. Then by definition $\lim\sup X_n = \sup E$ and $\lim\inf X_n = \inf E$. Antonym of "deepen" Since there is no word "shallowen", is there a good antonym of "deepen"? The meaning of "deepen" that I am referring to here is "to cause to become deeper." It doesn't necessarily refer to digging a hole. For example, a temporary deformation in a soft surface:     Putting the anvil on the mattress deepens the depression in it, but removing the anvil ______ it.   I would also be happy with an antonym of the intransitive version "to become deeper." Looking for illustrator script to swap all objects with another I have a map with small circles for over 200 cities. I need to change all of the circles into map pins. Is there a way to do this? I think it's a script maybe.   I know how to select all objects of the same appearance and give them a new graphic style but that will only let me change the color, stroke, etc. not replace with a new shape. Why does the following code in C work?  const char* str = NULL; str = "test"; str = "test2";   Since str is a pointer to a constant character, why are we allowed to assign it different string literals?  Further, how can we protect str from being modified?  It seems like this could be a problem if, for example, we later assigned str to a longer string which ended up writing over another portion of memory.  I should add that in my test, I printed out the memory address of str before and after each of my assignments and it never changed.  So, although str is a pointer to a const char, the memory is actually being modified.  I wondered if perhaps this is a legacy issue with C? FoxTrot Bill Amend Problems So I found this on the Wolfram website today:     So I was wondering about how one might be able to (if possible) solve those four problems by hand. Here are the problems, $\LaTeX$ed:    $ \lim_{x \to +\infty} \dfrac {\sqrt{x^3-x^2+3x}}{\sqrt{x^3}-\sqrt{x^2}+\sqrt{3x}} $ $ \displaystyle\sum_{k=1}^{\infty} \dfrac {(-1)^{k+1} k^2}{k^3+1} $  $ \dfrac {\mathrm{d}}{\mathrm{d}u} \left[ \dfrac {u^{n+1}}{(n+1)^2} \cdot \left[ (n+1) \ln u - 1 \right] \right] $  $ \displaystyle\int_0^{2\pi}\displaystyle\int_0^{\frac{\pi}{4}}\displaystyle\int_0^4 \left( \rho \cos \phi \right) \rho^2 \sin \phi \, \mathrm{d}\rho \mathrm{d}\phi \mathrm{d}\theta$     Ideas   The degree of the numerator is $\frac{3}{2}$. The degree of the denominator is $\frac{3}{2}$. The expression is of an indeterminate form, namely $\frac{\infty}{\infty}$, so we use l'Hoptial's Rule.  No ideas, really.  Derivatives are always pretty easy, although this one is a bit bashy. Basically bash Product and Chain Rules, etc.  Integration by Parts bash? The $\mathrm{d}\theta$ part is very trivial. I mean for the $\rho$ and $\phi$. You can't see the question owner's special color I know that SZ0 makes vertices straightened on the z-axis, but I'm wondering if there's a way to make vertices into a complete circle on the z-axis with a hotkey? This is a homework problem and I'm having trouble just getting a basic understanding.  I understand that $S_6$ is a symmetric group of degree $6$.  I'm not sure how to start looking for elements. $G$ solvable $\implies$ composition factors of $G$ are of prime order. I'm trying to prove the equivalency of the following definitions for a finite group, $G$:  (i) $G$ is solvable, i.e. there exists a chain of subgroups $1 = G_0  \trianglelefteq G_1 \trianglelefteq \cdots \trianglelefteq G_s = G $ such that $G_{i+1}/ \ G_i$ is abelian for all $0 \leq i \leq s-1$  (ii) $G$ has a chain of subgroups $1 = H_0  \trianglelefteq H_1 \trianglelefteq \cdots \trianglelefteq H_s = G $ such that $H_{i+1} /\  H_i$ is cyclic for all $0 \leq i \leq s-1$.  (iii) All composition factors of $G$ are of prime order.  (iv) G has a chain of subgroups $1 = N_0  \trianglelefteq N_1 \trianglelefteq \cdots \trianglelefteq N_t = G $ such that each $N_i$ is a normal subgroup of $G$, and $N_{i+1}/ \ N_i$ is abelian for all $0 \leq i \leq t-1$.  It was simple to show that (iii) $\implies$ (ii) and (ii) $\implies$ (i). Now, I'm trying to prove that (i) $\implies$ (iii), and I'm getting stuck.   I know that If $G$ is an abelian simple group, then $|G|$ is prime, so all I need to show is that each $G_{i+1}/ \ G_i$ in the definition of solvable is simple.  If I knew that $1 = G_0  \trianglelefteq G_1 \trianglelefteq \cdots \trianglelefteq G_s = G $ were a composition series, then each $G_{i+1}/ \ G_i$ would be simple by definition. But the definition of solvable doesn't assume a composition series. I know every group has a unique composition series, but I'm not sure how to connect that to the subgroups in the definition of solvable.   More generally, I guess I just don't understand how being abelian connects to being of simple or of prime order.  Any pushes in the right direction would be appreciated! Why is the application of probability in  (QM) fundamentally different from its application in other areas? QM applies probability according to the same  as in other areas of physics, engineering, etc.  Why is there a difference?  Naively one would assume one of these possibilities:   It is not the same probability (theory?) It is a matter of interpretation (of the formalism?) Something else?   Many answers (which I am still studying) focus on the fact that the combined probability of two mutually-exclusive events in QM is not equal to the sum of the probabilities of each event (which holds classically by definition). This fact (appears to) makes the formulation of another probability (a quantum one) a necessity.   Yet this again breaks down to assumed independent, if this is not so, the "classic probability" is applicable (as indeed in other areas). This is one of the main points of the question. How to prove this sequent using natural deduction? How do I prove $$S\rightarrow \exists xP(x) \vdash \exists x(S\rightarrow P(x))$$ using natural deduction? Just an alignment of which axioms or rules that one could use would be much appreciated. I'm stuck on a question which asks to prove that any continuous integer-valued function of a real variable is constant. In my lecture notes we are told that a map is continuous if the preimage of any open set is open.  How do I use this to answer the question? A full answer would be greatly appreciated as I can't seem to figure out how to solve it in my  notes, in analysis books or anywhere online. Does Earth's Rotation Affect Its Shape? The question I am working on is, &quot;Consider the following. (a) Find the angular speed of Earth's rotation about its axis. rad/s (b) How does this rotation affect the shape of Earth?&quot;  I am fully capable of solving part (a); however, I am not sure how to describe the effect earth's rotation on its shape. I tried to search my textbook for the answer, but could not find anything. Is there an actual effect on the shape? Please stop bounties from turning off community moderation Possible Duplicate:                tl;dr: Please get rid of "This question has an open bounty and cannot be closed"  Questions with bounties on them can't be closed:    This is by design, and the recommended course of action is to flag for moderator attention, at which point they'll decide whether to refund the bounty and close the question or not.   But why should a bounty disable regular community moderation?  We should be able to cast close votes on bountied questions as usual, and if a question gets enough, the bounty's refunded and the question closed.  An obvious benefit would be reduced burden on moderators, but I doubt that this is really a significant part of their workload.  More important is allowing the entire community's wisdom to be brought to bear.  Consider this question:      Having a simple MFC application with web browser controller that navigates to some site and then to another one on and on.      Using a powerfull machine (16 cores and lots of memory) OS is Server 2008 R2. I can see when launching my app over 30 instances I'm getting the OS UI (each window including my app, mspaint, taskmgr etc..) become very sluggish and slow.      I have monitored the machine resources (CPU, memory and GDI objects) but it seems that all of them are not even close to be in some level of stress.      What is the problematic resource that influence the machine in such way?      10x, Guy   It doesn't look like a good question: somewhat poorly written, vague, not a ton of information, etc.  I would vote to close this question.  However, I don't do much work with MFC and maybe there's something I'm missing.  (I can readily imagine a similarly bad looking question with the extremely concrete answer: .)  I'm comfortable casting a vote to close, not closing unilaterally.  Flagging for a moderator just passes the buck to them, when the correct action is letting the community weigh in. For wall-sized graphics and large banners (e.g. 3m × 5m), what is an acceptable PPI for print? As I understand it 300 ppi is the typical for 'small' artworks (esp. for clean text resolution). However, for small artworks, the audience usually engages at a much closer distance. Therefore, in the interests of keeping a bitmap file down to a reasonable size, can you get away with a much-reduced PPI for a large format/banner print? Why does Stack Exchange use Imgur over Amazon S3 or Azure? What benefit does  offer over , , etc. for image hosting?   Is it the simplicity of integration? The cost model? What's better about using a "gateway"? How to remove a watermark from a PDF file? I thought this would be a simple task, but it turned out the other way.  The watermark is the very same (overlapping, but transparent) image on every single page. I created the PDF file myself (so no copyright worries here) using PDFCreator 0.9.8.  I have already tried my friend's Adobe Acrobat Pro, but it didn't work. It tries to remove it, but it can't. I tried to remove header/footer, etc., but the watermark just won't disappear.    How can I remove the watermark? QGIS ->ArcGIS Server configuration possible? Is it possible to connect a QGIS Desktop 1.8.0 to an ArcGIS Server 10.0 ? and of course publish services on it?.   The configuration would be like this Quantum GIS-> ArcGIS Server 10.0 on Amazon EC2+ POstgreSQL (+PostGIS)-> web app.   Is it possible to create a configuration like this? Do you think I could use it for networking?