I have deployed a webapp named "webappName.war" by putting the war file in /tomcat/webapps. Tomcat successfully extracted that and I've tested my app using "localhost:8080/webappName/..." . But a few days later I've decided to change the deployed app so I simply removed the webappName.war and /webapps/webappName . I thought that's enough to undeploy a webapp. But that old webapp still exists!!!!! I can see it's row in "/localhost:8080/manager" Application table and I can test it using "/localhost:8080/webappName" !!!!!!! There isn't any folder or war in "tomcat/webapps" but the application exists and I can not deploy my new webapp. What should I do? I really need to undeploy that app and fill the context with another one.

How do I get Tomcat to remove the web application artifacts when using the Manager to undeploy the application?    I am using Tomcat 6.0.18. The application was deployed using the tomcat-maven-plugin 1.0-SNAPSHOT but the behavior is the same through the maven plugin or the web interface.  The Tomcat documentation provides warnings on how undeploy should behave on the  .  The war file can be removed; however, the unpacked application directory remains preventing a redeploy.


This is a follow-up from a :  My girlfriend had a 6-month visa for the UK, which expired in December. She reapplied last week, and this time it was denied. Mainly it seems because her employment has changed, and admittedly the sums she presented didn't tally up.  It seems now the best thing to do is wait 6 months because then her employment and payslips will look consistent (her employer is going to help with this).  So is this the best thing to do, wait 6 months and reapply for same type of visa? With me down as the sponsor (last time she put herself down to pay for the trip, then her mum, then my details, and it seems my details and letter were largely ignored).  It seems that doing the form by herself and trying to be honest and transparent created a problem.  She has a Schengen visa which lasts through until the summer, so seeing her won't be impossible, but the strain is going to be tremendous. I am a UK citizen with full-time employment, and apart from going to see her in Russia and quick and expensive trips in Europe, I just don't know what I can do to make sure I've explored all options and done the best I can.  Anything at all in terms of advice is appreciated, but I guess mainly, would it change if I put myself as sponsor and fill in myself? Should I definitely wait? Is there anything I can do to have her here sooner? Or at least to ensure same problems don't arise again? If we were to go down the route, is marrying abroad and then having her come through a spouse application the most fail-safe way?  Thank you so much to all.

Many of the UK visa refusals we see here share a common pattern and the prevailing reasons refer to V 4.2 (a) and (c).    I do understand that, while the applicants may describe very different individual circumstances, there's a consistent pattern and, broadly, fall into specific categories:    Credibility (lifestyle, lack of ties, visit history, lies & omissions) Funding (insufficient funds, provenance of funds, funds parking) Sponsorship (family, friends, employer)   Question: What most commonly triggers a UK visa refusal where V 4.2 (a) and (c) are given as the grounds?  Secondarily: Given that there is a clear pattern, to what extent are these refusals predictable? Does sponsorship make a difference? Is there a set of personal circumstances, however abstract, where a refusal is all but guaranteed? For example, why do those we see here on TSE who sought entry for the PLAB or British Army appear to be refused with a common theme? Is there a uniform shortcoming or is it just discrimination?   PLAB: What is about applications for a visa, for the purpose of sitting the Professional and Linguistic Assessments Board (PLAB) exam, that seem to invite refusals. After all, the test is given so that international medical graduates can show that they qualify to practise medicine in the UK. The first part, PLAB 1, can be taken in centres outside of the UK. However, PLAB 2 can be taken only in the UK. Why can't you can't get a visa just to sit the exam, promising that you'll leave immediately after?    British Army: Since Commonwealth citizens are eligible to apply online to join, even those who don't reside in the UK, why is it so difficult to get a visa just to attend an interview to see whether you are suitable? Even with an invitation from the Army, such visa applications seem to be unsuccessful. Isn't a career in the British Army a valid reason?     Lastly:  After such a refusal, what approaches would increase the chance of a successful application?


I wanted to copy .ssh folder from my old computer to a new machine. So on my new ubuntu I mounted my APFS drive (just read-only support) and did:  ➜  adam_old ls -ld .ssh drwx------ 1 501 dialout 6 dub  3 13:16 .ssh  ➜  adam_old sudo cp -vr .ssh ~/.ssh     cp: cannot stat '.ssh': Permission denied   and got permission denied for root. But when i removed sudo:  ➜  adam_old cp -vr .ssh ~/.ssh  '.ssh/known_hosts' -> '/home/adam/.ssh/.ssh/known_hosts' '.ssh/pi@hrasp_id_rsa' -> '/home/adam/.ssh/.ssh/pi@hrasp_id_rsa' '.ssh/pi@hrasp_id_rsa.pub' -> '/home/adam/.ssh/.ssh/pi@hrasp_id_rsa.pub' '.ssh/config' -> '/home/adam/.ssh/.ssh/config' '.ssh/pi@rasp_id_rsa' -> '/home/adam/.ssh/.ssh/pi@rasp_id_rsa' '.ssh/pi@rasp_id_rsa.pub' -> '/home/adam/.ssh/.ssh/pi@rasp_id_rsa.pub'   It worked. I don't get it (I thought root has access to everything).   Has it something to do with the old drive was also a unix system with its own permissions? (We can see user 501 and group dialout as owners of .ssh in the first snippet.)  So I checked groups to which root and my account 'adam' belong, and their IDs:  ➜  adam_old cat /etc/group | grep dialout  dialout:x:20:  ➜  adam_old cat /etc/passwd | grep -E '^(root|adam)' root:x:0:0:root:/root:/bin/bash adam:x:1000:1000:Adam,,,:/home/adam:/usr/bin/zsh   (groups 0 is group 'root' and group 1000 is group 'adam')  still I have no idea why it didn't work for root, but did for 'adam'.  EDIT: Found out that I actually copied old drive's ~/.ssh to new drive's ~/.ssh/.ssh (but that doesn't matter for the question).

I use a FUSE filesystem with no problems as my own user, but root can't access my FUSE mounts.  Instead, any command gives Permission denied. How can I give root the permission to read these mounts?  ~/top$ sudo ls -l total 12 drwxr-xr-x 2 yonran yonran 4096 2011-07-25 18:50 bar drwxr-xr-x 2 yonran yonran 4096 2011-07-25 18:50 foo drwxr-xr-x 2 yonran yonran 4096 2011-07-25 18:50 normal-directory ~/top$ fuse-zip foo.zip foo ~/top$ unionfs-fuse ~/Pictures bar   My user, yonran, can read it fine:  ~/top$ ls -l total 8 drwxr-xr-x 1 yonran yonran 4096 2011-07-25 18:12 bar drwxr-xr-x 2 yonran yonran    0 2011-07-25 18:51 foo drwxr-xr-x 2 yonran yonran 4096 2011-07-25 18:50 normal-directory ~/top$ ls bar/ Photos   But root can't read either FUSE directory:  ~/top$ sudo ls -l ls: cannot access foo: Permission denied ls: cannot access bar: Permission denied total 4 d????????? ? ?      ?         ?                ? bar d????????? ? ?      ?         ?                ? foo drwxr-xr-x 2 yonran yonran 4096 2011-07-25 18:50 normal-directory ~/top$ sudo ls bar/ ls: cannot access bar/: Permission denied   I'm running Ubuntu 10.04: I always install any update from Canonical.  $ uname -a Linux mochi 2.6.32-33-generic #70-Ubuntu SMP Thu Jul 7 21:13:52 UTC 2011 x86_64 GNU/Linux $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 10.04.3 LTS Release:    10.04 Codename:   lucid   Edit: removed the implication that root used to be able to access the mounts. Come to think of it, maybe my scripts never tried to access the directory as root.


I'm trying too use JavaScripts "replace"-function to put tags around text given in between certain characters. Example:  str.replace(/\_(.*?)\_/gi, '$1');   Now this works fine but I want the "_"-characters to be given as a variable. For example:  var und = "_"; str.replace(/\und(.*?)\und/gi, '$1');   My question is how can I do that?  Thnx in advance!

I would like to create a String.replaceAll() method in JavaScript and I'm thinking that using a regex would be most terse way to do it.  However, I can't figure out how to pass a variable in to a regex.  I can do this already which will replace all the instances of "B" with "A".  "ABABAB".replace(/B/g, "A");   But I want to do something like this:  String.prototype.replaceAll = function(replaceThis, withThis) {     this.replace(/replaceThis/g, withThis); };   But obviously this will only replace the text "replaceThis"...so how do I pass this variable in to my regex string?


I have created an android chat app using firebase - the app works fine but when first opened, the app crashes in login page but after this the app restarts and works fine. Please help me with a solution because I am a beginner in this field tell me what I should change to make it work   My logcat: beginning of crash     Caused by: java.lang.NullPointerException: Attempt to invoke virtual   method 'java.lang.String   com.google.firebase.auth.FirebaseUser.getUid()' on a null object   reference at   com.dndna.chat_rooms.views.base.BasePresenter.getCurrentUserId(BasePresenter.java:78)           at com.dndna.chat_rooms.views.main.MainPresenter.checkPendingNotification(MainPresenter.java:198)           at com.dndna.chat_rooms.views.main.MainActivity.onResume(MainActivity.java:262)   at   android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1456)           at android.app.Activity.performResume(Activity.java:7614)           at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4412)   The problem seems to be in these locations  public void checkPendingNotification() {     if (getCurrentUserId() != null)         notifyManager.checkPendingNotification(this::showBadgeAt); }   and  if (presenter != null) {     presenter.checkPendingNotification(); }   and  protected String getCurrentUserId() {     FirebaseAuth.getInstance();     return FirebaseAuth.getInstance().getCurrentUser().getUid(); }

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


In Episode I: The Phantom Menace, young Anakin Skywalker and his mother explain how the Tatooine slave owners prevent the slaves from escaping:  SHMI: All slaves have a transmitter placed inside their bodies somewhere. ANAKIN: I've been working on a scanner to try and locate mine. Any attempt to escape, and they blow you up!  Anakin is eventually freed by Qui-Gon - and Watto respects the terms of the bet because he's afraid of potential retribution from the Hutts if he didn't. But there's no scene that shows or explains what happens to Anakin's implant. Does the adult Darth Vader still have an explosive implanted somewhere in his body? If so, and the Rebellion happened to discover the exact frequency or signal needed to detonate the explosive, could they remotely assassinate Darth Vader?

In The Phantom Menace, Anakin talks about having a bomb inside of him and, should he try to escape, Watto can simply blow him up.     SHMI: All slaves have transmitters placed inside their bodies somewhere.       ANAKIN: I've been working on a scanner to try and locate them, but no    luck.       SHMI: Any attempt to escape...       ANAKIN: ...and they blow you up...poof!   Did they ever remove this bomb or device from Anakin? Did Watto still retain the ability to blow up Anakin?


I have 1TB hard drive and 4GB RAM. I want to know the whole procedure from scratch i.e. which OS to be installed first and how to make the partitions. I'll be installing both OS from bootable usb drives. Please help me out.

I would like to see a full how-to guide on how to install Ubuntu.


I tried to derive the formula second derivatives from Wikipedia:     $$f''\left( x\right) =\lim _{h\rightarrow 0}\dfrac {f\left( x+h\right) -2f\left( x\right) +f\left( x-h\right) }{h^{2}}$$   Let $y=f(u)$ and using first principles, since $$\dfrac {dy}{du}=\lim _{k\rightarrow 0}\dfrac {f\left( u+k\right) -f\left( u\right) }{k}$$ therefore, $$\dfrac {d^{2}y}{dx^{2}}=\dfrac {d\left( \dfrac {dy}{du}\right) }{dx}= \lim _{h\rightarrow 0} \dfrac{\left.\dfrac {dy}{du}\right|_{u= x+h}-\left.\dfrac {dy}{du}\right|_{u=x}}{h}\\ = \lim _{h\rightarrow 0}\dfrac {\lim _{k\rightarrow 0}\dfrac {f\left( x+h+k\right) -f\left( x+h\right) }{k}-\lim _{k\rightarrow 0}\dfrac {f\left( x+k\right) -f\left( x\right) }{k}}{h} \\ = \lim _{h\rightarrow 0}\dfrac {\lim _{k\rightarrow 0}\dfrac {f\left( x+h+k\right) -f\left( x+h\right) -f\left( x+k\right) +f\left( x\right) }{k}}{h} $$ And I’m stuck with a stacked limit of two bound variables. So what have I done wrong?

I've been trying to understand how the second order derivative "formula" works:  $$\lim_{h\to0} \frac{f(x+h) - 2f(x) + f(x-h)}{h^2}$$  So, the rate of change of the rate of change for an arbitrary continuous function. It basically feels right, since it samples "the after $x+h$ and the before $x-h$" and the $h^2$ is there (due to the expected /h/h -> /h*h), but I'm having trouble finding the equation on my own.  It's is basically a derivative of a derivative, right? Newtonian notation declares as $f''$ and Leibniz's as $\frac{\partial^2{y}}{\partial{x}^2}$ which dissolves into:  $$(f')'$$ and $$\frac{\partial{}}{\partial{x}}\frac{\partial{f}}{\partial{x}}$$  So, first derivation shows the rate of change of a function's value relative to input. The second derivative shows the rate of change of the actual rate of change, suggesting information relating to how frequenly it changes.  The original one is rather straightforward:  $$\frac{\Delta y}{\Delta x} = \lim_{h\to0} \frac{f(x+h) - f(x)}{x + h - x} = \lim_{h\to0} \frac{f(x+h) - f(x)}{h}$$  And can easily be shown that $f'(x) = nx^{n-1} + \dots$ is correct for the more forthcoming of polynomial functions. So, my logic suggests that to get the derivative of a derivative, one only needs to send the derivative function as input to finding the new derivative. I'll drop the $\lim_{h\to0}$ for simplicity:  $$f'(x) = \frac{f(x+h) - f(x)}{h}$$  So, the derivative of the derivative should be:  $$f''(x) = \lim_{h\to0} \frac{f'(x+h) - f'(x)}{h}$$  $$f''(x) = \lim_{h\to0} \frac{  \frac{ f(x+2h) - f(x+h)}{h} - \frac{ f(x+h) - f(x)}{h}  }{h}$$  $$f''(x) = \lim_{h\to0} \frac{  \frac{ f(x+2h) - f(x+h) - f(x+h) + f(x)}{h}  }{h}$$  $$f''(x) = \lim_{h\to0} \frac{  f(x+2h) - f(x+h) - f(x+h) + f(x)  }{h^2}$$  $$f''(x) = \lim_{h\to0} \frac{  f(x+2h) - 2f(x+h) + f(x)  }{h^2}$$  What am I doing wrong? Perhaps it is the mess of it all, but I just can't see it. Please help.


I have a Schengen 'C' visa for MULT entries. The duration of stay is eight days and the validity is from 15th July to 27th July.  Would it allow me the "90-day, short-stay visa"?  I am guessing not, but wanted to confirm.

I have a multiple entry Schengen visa issued by the German consulate in Kolkata that is valid until 26.08.2014. Does this mean I have return within 26.08.2014?   If I enter before 26.08.2014, then can I stay up to another 10/15 days?


I am developing an application in C and it must accept characters from every language. I am targeting Linux/Windows. What is the best way to implementing this, considering that performance is important in this case?

What prerequisites are needed to do strict Unicode programming?  Does this imply that my code should not use char types anywhere and that functions need to be used that can deal with wint_t and wchar_t?  And what is the role played by multibyte character sequences in this scenario?


What's the process to propose a new tag? I see lots of Amazon related tags referring to specific products, and found that the CloudWatch tag is missing (and couldn't add it due to lack of reputation).

Can someone please create the tag  on our site? We need to have it because        Foo is a recent/upcoming release / edition / model / episode of a popular, established OS / board game / bike brand / TV show   Foo is a hot new language / ingredient / game   we're currently using some other tag for questions about Foo, but it's causing ambiguity with a separate thing that's also named Foo      This is not a joke post. We get a lot of feature requests that ask for this or that tag to be created, and every time, a discussion ensues wherein people explain that there is no "tag creation department" and that community members create tags just by using them. I'm posting this "question" so that future requests of that type can be closed as a duplicate of this, saving time and eliminating redundant conversations for everyone involved.     See also:


I have a C++ project with several classes each of them declared and defined in separated files. One by one, each file is compiled to .o file, however when I try to link them to get an executable, I get undefined reference error for one class member.  I'm adding a fake code that represent the situation to be more clear:  //filea.hpp #include "fileb.hpp" class A; typedef B<A> BA; class A { protected:    static BA *b; public:     static void setBA(){b = new BA();} };   /filea.cpp #include "filea.hpp" BA* A::b = nullptr; // will be initialized in main    //fileb.hpp #include <vector>  template <class A> class B {    std::vector<A*> v; public:    void some_stuff(A*); };   //fileb.cpp #include "fileb.hpp"  template <class A> void B<A>::some_stuff(A* a){     this->v.push_back(a);     }   //filec.hpp #include "filea.hpp"  class C: public A {   public:   void foo(); };    //filec.cpp #include "filec.hpp" void C::foo () {   this->b->some_stuff((A*) this);  }   // main.cpp #include "filec.hpp"  int main () {    A::setBA();    C c;    c.foo(); };   and my makefile is :  EXECUTABLE_NAME := execfile CFLAGS := -std=c++14 -g -pthread  CC := g++ DEPS := fileb.hpp   %.o: %.c %.h $(DEPS)     $(CC) -c -o $@ $< $(CFLAGS)  all: fileb.o filea.o filec.o     $(CC) fileb.o filea.o filec.o main.cpp -o $(EXECUTABLE_NAME) $(CFLAGS)    When I do make all, filea, fileb and filec compiled successfully. However, in linking and compiling to executable phase it gives   g++ fileb.o filea.o filec.o main.cpp -o he2ExecFile -std=c++14 -g -pthread filec.o: In function `C::foo()': filec.cpp:(.text+0x1e): undefined reference to `B<A>::some_stuff(A*)' collect2: error: ld returned 1 exit status Makefile:11: recipe for target 'all' failed make: *** [all] Error 1   While searching, found that not initializing static member causes similar error but it says undefined reference for A::b, which is completely different.  I looked same answer page, but didn't solve my problem.

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


The title basically says it all.  Is it possible to associate with each pair of reals, another unique real?  I guess you could say I'm looking for functions of two real arguments that return a distinct real number.

Could any one give an example of a bijective map from $\mathbb{R}^3\rightarrow \mathbb{R}$?  Thank you.


I have a notebook with Windows 10; the hard drive has 745 gigs. I would like to have 200 gigs for Ubuntu 16.04, the rest for Windows. When I try to install Ubuntu 16.04 it looks like Windows will only get 500 megs, which is not enough. How do I do that, this installation is very very confusing. BR, Lloyd


This question was already asked here     ...but there were no satisfactory answers.   However that was from a few years ago.   Since that time we've had new restrictions put in on bringing laptop computers and cameras into the passenger cabin on flights from the ME to the US and UK, and there are heavy rumours that the US government is about to place such restrictions on all flights from Europe.  I travel for photography, so I routinely bring a pair of camera bodies (one for backup) and a bunch of lenses. (I also travel with a laptop)  I've always brought them on board as carry-on.    The total value of the gear I bring is typically $20K-30K, with maybe $6-10K of that my DSLR bodies.     The travel insurance companies I've contacted won't sell me anywhere near that much insurance for checked luggage.  What do people currently do traveling on routes from the ME to the US and UK, for example?

While I plan to travel with a , I am yet to find an insurance that covers much of significant value.  We have coverage that comes with credit cards with limits of $200 to $500 per item, depending on the card. Airlines also have a limit around that amount even for upgraded insurance and searching known travel insurance companies, I found similar coverage.  Does insurance exist for checked luggage between $5000 and $10000 CDN ($4000 - $8000 USD)? If so, who offers such coverage?


What is the difference between 'I have gone to the restaurant' and 'I had gone to the restaurant'

Non-native speakers often get confused about what the various tenses  and aspects mean in English. With input from some of the folk here I've put together a diagram that I hope will provide some clarity on the matter.  I offer it as the first answer to this question. Consider it a living document. Input is welcome, and good suggestions will be  incorporated into the diagram.    Nota bene: What this is not is a discussion of whether there are  more than two tenses in English. , to which this question is not intended to supply arguments one way or the other.  Here, the aim is to provide an overview of what constructions English-speaking people use for conveying information about actions referring to past, present, and future, and to provide it first and foremost to precisely the people who are likely to use "tense" as a catch-all term in their search, rather than to linguists who know better.  Breaking News There is now an excellent ELU blog article titled  . It is highly recommended reading.


Iam stuck with this proof. There seems to be no property to help. If $\sum_1^\infty|a_n|<\infty$ then show that $\sum_1^\infty{a_n^2}<\infty$ and that the reverse isnt true.

I'm trying to re-learn my undergrad math, and I'm using Stephen Abbot's Understanding Analysis. In section 2.7, he has the following exercise:  Exercise 2.7.5 (a) Show that if $\sum{a_n}$ converges absolutely, then $\sum{a_n^2}$ also converges absolutely. Does this proposition hold without absolute convergence?  I'm posting about this here because my answer to that last question about whether the proposition holds without absolute convergence is "Yes", but my suspicions are raised by him merely asking the question. Usually questions like this are asked to point out that certain conditions are necessary in the statement of propositions, theorems, etc. I just want to see if I'm missing something here.  Anyway, here's how I prove the absolute convergence of $\sum{a_n^2}$, and note that I never use the fact that $\sum{a_n}$ is absolutely convergent:  Proof: Let $s_n = \sum_{i=1}^n{a_n^2}$. I want to show that $(s_n)$ is a Cauchy sequence. So, let $\epsilon > 0$ and $n > m$, and consider, \begin{equation}   \begin{aligned}     |s_n - s_m| &= |(a_1^2 + a_2^2 + \cdots a_n^2) - (a_1^2 + a_2^2 + \cdots a_m^2)|\\                 &= |(a_{m+1})^2 + (a_{m+2})^2 + \cdots + a_n^2|\\                 &= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\   \end{aligned} \end{equation} Now, since $\sum{a_m}$ converges, the sequence $(a_m)$ has limit 0. Therefore I can choose an $N$ such that $|a_m| < \sqrt{\epsilon/n}$ for all $m > N$. So for all $n > m> N$,  we have, \begin{equation}   \begin{aligned}     |s_n - s_m| &= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\                 &< \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n}}\right)^2\\                 &< \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2\\                 &= \epsilon   \end{aligned} \end{equation} Therefore $(s_n)$ is Cauchy and $\sum{a_n^2}$ converges. And since $\sum{a_n^2} = \sum{|a_n^2|}$, the series $\sum{a_n^2}$ is absolutely convergent. ∎  Am I doing something wrong here? Am I right in thinking that $\sum{a_n}$ need not be absolutely convergent for $\sum{a_n^2}$ to be absolutely convergent?


I basically want to write my ping statistics into a file. So far, I accomplished this with ping adress | awk '{ print strftime("[%d.%m.%Y %H:%M:%S]"), $0}' > textfile but it would be more handy to be able to look at the output without having to interrupt the process before. I am also aware that this command does not write stderr into my textfile. I came up with that part while writing this question.  The command or script should basically behave like this:   $ command > textfile [15.08.2017 00:17:07] PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data. [15.08.2017 00:17:07] 64 bytes from 8.8.8.8: icmp_seq=1 ttl=44 time=11.5 ms [15.08.2017 00:17:08] 64 bytes from 8.8.8.8: icmp_seq=2 ttl=44 time=11.5 ms ^C $ cat textfile [15.08.2017 00:17:07] PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data. [15.08.2017 00:17:07] 64 bytes from 8.8.8.8: icmp_seq=1 ttl=44 time=11.5 ms [15.08.2017 00:17:08] 64 bytes from 8.8.8.8: icmp_seq=2 ttl=44 time=11.5 ms

I'm using bash script on AMazon Linux.  When I want to redirect stderr and stdout to a file, I can run  ./my_process.pl &>/tmp/out.txt   Is there a way I can redirect this output to a file and continue to see it on the console (in my shell)?  How is this done?


I'm trying to fix a corrupted sdcard vfat filesystem (used in an Android device) using fsck.  The sdcard just stopped working one day (the file browser doesn't show it and it's not visible in Android settings), I tried re-inserting it. When that didn't work I used my sdcard reader on my Linux machine. There I was able to mount and browse the filesystem, but after inserting it into Android it still didn't show up. I inserted it back to my Linux machine and the filesystem was gone (the device was recognized though). So I gave up and used cfdisk to create a new (ext4) partition. After doing that and quitting cfdisk, the previous filesystem (vfat) was recovered and the files could be browsed and viewed. I have no idea what's going on.  Current lsblk and fsck output:  > lsblk -f NAME         FSTYPE LABEL UUID                                 FSAVAIL FSUSE% MOUNTPOINT mmcblk0                                                                        ├─mmcblk0p1  vfat         6AEE-8592                                            ├─mmcblk0p2  swap         bf2ed99b-104e-4a91-8970-b392a19dccc8                [SWAP] └─mmcblk0p3  ext4         0cdff248-07ef-48aa-8c67-b9c86c6f8aa9     11G    55% / mmcblk0boot0                                                                   mmcblk0boot1                                                                   mmcblk1                                                                        └─mmcblk1p1  vfat         35B9-1806                                              > sudo fsck -av /dev/mmcblk1p1 fsck from util-linux 2.34 fsck.fat 4.1 (2017-01-24) Checking we can access the last sector of the filesystem Boot sector contents: System ID "android " Media byte 0xf0 (5.25" or 3.5" HD floppy)        512 bytes per logical sector      32768 bytes per cluster         74 reserved sectors First FAT starts at byte 37888 (sector 74)          2 FATs, 32 bit entries    1930752 bytes per FAT (= 3771 sectors) Root directory start at cluster 2 (arbitrary size) Data area starts at byte 3899392 (sector 7616)     482633 data clusters (15814918144 bytes) 16 sectors/track, 4 heads          0 hidden sectors   30896128 sectors total Reclaiming unconnected clusters. Checking free cluster summary. Free cluster summary wrong (189038 vs. really 118813)   Auto-correcting. Performing changes. /dev/mmcblk1p1: 1050 files, 363820/482633 clusters   For some reason, fsck returns with exit code 1  > echo $? 1   Repeating the fsck command produces the exact same output.  Is there anything I can do about this or is the SD card dead?

I am trying to help a friend who is very concerned that she has just lost all of the data on her 32GB SanDisk microSD card.  I told her I would post this and see if anyone could offer help.  Here are the details:   The SanDisk microSD card is less than two years old.  Probably only about a year old.  The store will take it back, but that doesn't really help.  She wants her data. She used the card in her Samsung Galaxy S4 smartphone for over a month.  The phone was never exposed to water or temperature extremes. Today, her phone suddenly said something like "Your SD card is blank or an unsupported format". Her phone was then unable to read the SanDisk microSD card at all.   Here's what she has tried:   Rebooting her phone.  Had no effect. Taking out the SanDisk microSD card and putting it inside a full-size SD card adapter, and inserting it into a Windows 7 SP1 computer.  The computer did not recognize its presence at all. Putting the SanDisk microSD card into a USB 2.0 external card reader and inserting the card reader into a USB port on a Windows 7 SP1 computer.  The computer recognized the card reader and installed drivers for it.  The card reader shows up as 'Removable Disk' in Windows Explorer.  Clicking on 'Removable Disk' in Windows Explorer results in the error "Insert disk: Please insert a disk into the Removable Disk". After trying #3, tried opening the 'Removable Disk' in FreeCommander.  Doing so results in the error "The device is not ready".   She does not have access to a linux box, but does have access to her Android phone.  What can she do to recover the data on her 32GB SanDisk microSD card?


Problem: Let $A$ and $B$ be $n\times n$ real symmetric positive definite matrices and $S_{A}= \{x\in \mathbb{R}^n:x^TA^{-1}x \leq 1\}$ and $S_{B}= \{x\in \mathbb{R}^n:x^TB^{-1}x \leq 1\}$. Show that $S_{A} \subseteq S_{B}$ iff $B \succeq A$.  Definition: $B \succeq A \Rightarrow B-A \succeq 0$, in other words $B-A$ is positive semidefinite. I seem to be getting the opposite result. I do: if $S_{A} \subseteq S_{B}$ then $x^TA^{-1}x \leq x^TB^{-1}x$ and so $0 \leq x^TB^{-1}x-x^TA^{-1}x$ which means that $0 \leq x^T(B^{-1}-A^{-1})x$. This means that $(B^{-1}-A^{-1})$ is positive semidefinite and thus $B^{-1} \succeq A^{-1}$. But I know that (and previously proved) if $B^{-1} \succeq A^{-1}$ then $B \preceq A$, which is the opposite of what I am trying to prove. Where am I going wrong so far, and how do I proceed?

Assume $A \in \textbf{S}^n_{++}$, an ellipsoid centered at the origin given by $$\mathcal{E}_A = \{x\mid x^TA^{-1}x \leq 1\}$$ Then we have $\mathcal{E}_A \subseteq \mathcal{E}_B $ if and only if $B-A \succeq 0$. This is the proposition in the Boyd & Vandenberghe's  (pages 45-46). The authors gave only the result, without proof. How to prove it?


I just attempted to set up my Lenovo Thinkpad Twist to dual boot. It had Windows 8.1 pre-installed.  I burned Ubuntu 13.04 to a USB and booted from that. I partitioned the drives allocating 50 GB for the Ubuntu partition. Ubuntu itself works fine, however when I try to boot back into windows I get an error: can't find command 'drivemap' and error: invalid EFI file path.  It looks like the problem is that the partition created 4 separate file systems:   Lenovo_recovery 367MB Volume Windows8_OS WINRE_DRV.   There is a boot folder under the Windows8_OS file system, but I think that it is not being accessed by the boot menu.   Also, the boot menu only has an option for Windows 8 (loader) (on/dev/SDA4) and no Windows recovery environment. The parameters for this file are as follows:  setparams 'Windows 8 (loader) (on /dev/sda4)'  insmod part_gpt insmod ntfs set root='hd0,gpt4' if [ x$feature_platform_search_hint = xy ]; then     search --no-floppy --fs-uuid --set=root --hint-efi=hd0,gpt4 --hit-baremetal=ahci0,gpt4 FE3A79DE3A79947D else     search --no-floppy --fs-uuid --set=froot FE3A79DE3A79947D fi drivemap -s (hd0) ${root} chainloader +1   How do I fix this so that I can boot back into Windows 8?

I have got a newly bought ASUS N56V with Windows 8 preinstalled.  I needed to install Ubuntu so i partitioned the disk and after having disabled the Secure Boot option from Windows 8 i successfully installed Ubuntu 12.10 from a Live USB. The problem is that if i try to access both to Windows 8 (loader) and Windows Recovery System (loader) from the GRUB menu, these two errors show: can't find command 'drivemap' and invalid EFI file path and it goes back to the grub menu.  In conclusion I do not have access to my Windows 8 partition but can only use Ubuntu. How can I solve the problem? I am pretty new to the matter.  Thank you!


I had some case in which first seemed to change the value of Boolean and second didn't! Is there a real difference between the two:  boolean x = true;  if (x != true) {} if (!x) {}

I have a question about the meaning (evaluation) of Boolean variables in return statements in Java.  I know that:  if (var) { ... }   is the same as:  if (var==true) { ... }   In the second case we explicitly say var==true, but we don't need to do this, because Java evaluates var as true anyway. I hope I have understood this right.  My question is: is it the same when Boolean variables are returned? When we have a return statement?  For example, a task specifies: the method looksBetter() will return true only if b < a. My solution was:  public boolean looksBetter() {      if (b < a) {          return true;      } else {          return false;      } }   The simple answer was:  public boolean lookBetter() {       return b < a; }   So, it seems that here we have again this implicit assumption that in case b < a == true, the return of the method is true. I am sorry ... it seems very trivial, but I am somehow not comfortable with this, and I don't know why. Thank you.


I am running Ubuntu 12.10 alongside Windows 7 I can connect to the internet using ethernet but cannot detect any wireless networks. When I use Windows 7 I can connect fine. Any help would be greatly appreciated. The output for lspci -v | grep -iA 10 network was:  02:00.0 Network controller: Broadcom Corporation BCM43142 802.11b/g/n (rev 01) Subsystem: Dell Wireless 1704 802.11n + BT 4.0 Flags: bus master, fast devsel, latency 0, IRQ 11 Memory at c0500000 (64-bit, non-prefetchable) [size=32K] Capabilities: <access denied>   lsmod:  Module                  Size  Used by joydev                 17457  0  snd_hda_codec_hdmi     32007  1  snd_hda_codec_conexant    57842  1  rfcomm                 46619  12  bnep                   18140  2  parport_pc             32688  0  ppdev                  17073  0  lp                     17759  0  parport                46345  3 parport_pc,ppdev,lp coretemp               13400  0  kvm_intel             132759  0  kvm                   414070  1 kvm_intel ghash_clmulni_intel    13180  0  cryptd                 20403  1 ghash_clmulni_intel dell_wmi               12681  0  sparse_keymap          13890  1 dell_wmi psmouse                95552  0  dell_laptop            17369  0  dcdbas                 14438  1 dell_laptop microcode              22803  0  snd_hda_intel          33491  3  snd_hda_codec         134212  3        snd_hda_codec_hdmi,snd_hda_codec_conexant,snd_hda_intel snd_hwdep              13602  1 snd_hda_codec uvcvideo               76749  0  videobuf2_core         32851  1 uvcvideo videodev              120309  2 uvcvideo,videobuf2_core videobuf2_vmalloc      12860  1 uvcvideo videobuf2_memops       13368  1 videobuf2_vmalloc snd_pcm                96580  3 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec snd_seq_midi           13324  0  snd_rawmidi            30512  1 snd_seq_midi wmi                    19070  1 dell_wmi btusb                  18334  0  bluetooth             209199  22 rfcomm,bnep,btusb snd_seq_midi_event     14899  1 snd_seq_midi mac_hid                13205  0  snd_seq                61521  2 snd_seq_midi,snd_seq_midi_event snd_timer              29425  2 snd_pcm,snd_seq snd_seq_device         14497  3 snd_seq_midi,snd_rawmidi,snd_seq rts5139               356158  0  snd                    78734  16   snd_hda_codec_hdmi,snd_hda_codec_conexant,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,s    nd_rawmidi,snd_seq,snd_timer,snd_seq_device i915                  520519  3  drm_kms_helper         46784  1 i915 drm                   275528  4 i915,drm_kms_helper i2c_algo_bit           13413  1 i915 soundcore              15047  1 snd snd_page_alloc         18484  2 snd_hda_intel,snd_pcm serio_raw              13215  0  lpc_ich                17061  0  mei                    40690  0  video                  19335  1 i915 r8169                  61650  0    iwconfig:   eth0      no wireless extensions.  lo        no wireless extensions.   rfkill list all  0: hci0: Bluetooth Soft blocked: no Hard blocked: no

I have installed Ubuntu alongside Windows 8.1. But the wifi is not working in Ubuntu (perhaps the drivers are not present), which worked fine in windows. Also I cant connect with Ethernet since my laptop does not have an Ethernet port. So is there any way for me to connect to the internet in ubuntu? Edit: Output of the terminal command  lspci -knn | grep Net -A2:  vikram@vikram-Inspiron-11-3148:~$ lspci -knn | grep Net -A2 01:00.0 Network controller [0280]: Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] (rev 01)     Subsystem: Dell Device [1028:0018]     Kernel driver in use: bcma-pci-bridge vikram@vikram-Inspiron-11-3148:~$    I did what Pilot6 suggested. Here is the output:    vikram@vikram-Inspiron-11-3148:~$ sudo dpkg -i *.deb [sudo] password for vikram:  Selecting previously unselected package bcmwl-kernel-source. (Reading database ... 163804 files and directories currently installed.) Preparing to unpack bcmwl-kernel-source_6.30.223.141+bdcom-0ubuntu2_amd64.deb ... Unpacking bcmwl-kernel-source (6.30.223.141+bdcom-0ubuntu2) ... Selecting previously unselected package dkms. Preparing to unpack dkms_2.2.0.3-1.1ubuntu5.14.04_all.deb ... Unpacking dkms (2.2.0.3-1.1ubuntu5.14.04) ... Setting up dkms (2.2.0.3-1.1ubuntu5.14.04) ... Setting up bcmwl-kernel-source (6.30.223.141+bdcom-0ubuntu2) ... Loading new bcmwl-6.30.223.141+bdcom DKMS files... First Installation: checking all kernels... Building only for 3.16.0-30-generic Building for architecture x86_64 Building initial module for 3.16.0-30-generic ERROR (dkms apport): kernel package linux-headers-3.16.0-30-generic is not supported Error! Bad return status for module build on kernel: 3.16.0-30-generic (x86_64) Consult /var/lib/dkms/bcmwl/6.30.223.141+bdcom/build/make.log for more information. modprobe: FATAL: Module wl not found. update-initramfs: deferring update (trigger activated) Processing triggers for man-db (2.6.7.1-1ubuntu1) ... Processing triggers for initramfs-tools (0.103ubuntu4.2) ... update-initramfs: Generating /boot/initrd.img-3.16.0-30-generic vikram@vikram-Inspiron-11-3148:~$


I have entered Single user mode like 5min ago. Meanwhile I shut down the computer, tried to get back to Single user mode my pressing cmd+S and it doesnt work. It outputs the error saying Builduser() Error building user of type 0xffsomethinggoeshere  It worked 5min ago. All I did was to run some ls commands. What could be the problem?  Edit> Verbose mode doesnt work either.

I'm getting a strange message each time I boot. For a quick second before the Apple Logo appears I see the text:  BuildError(): error building a user of type 0x20010008   Then the Logo appears, and shortly after the Login screen. After which the following errors appear:  BuildError(): error building a user of type 0x20010008 **** ERROR _CreateMenuWithWithIdentifier no image for file: 1_flag_menu_item.png **** ERROR _CreateMenuWithWithIdentifier no image for file: 77_flag_other_menu_item.png **** ERROR UIFlagPickerRestoreState No state found for flag picker **** ERROR ArchiveViewCreateWithOptions ArchiveCopyPNGImage failed for file: preferences_good_samaritan_message_ribbon.png **** ERROR ArchiveViewCreateWithOptions ArchiveCopyPNGImage failed for file: logimui_bootprogressbar.png   In verbose boot this is in big text before the usual status messages that show loading of the OS.  I'm was running OS X 10.10.4, and this began once I upgraded to the GM Candidate of El Capitan 10.11, which is the newest and stable release. Haven't a clue about what it is.  Any ideas as to what these messages are?  Update: Fresh Install  I just wiped my computer and did a fresh install of 10.11 GM El Capitan. Still showing up. Seems to be an issue of the new OS.


Is it safer to only use local variables within your JavaScript code?  As I understand variables declared within the $(document).ready(function () {code here...} block are local. Meaning these cannot be accessed or changed by other scripts?  Also, if a variable is declared global but assigned a value locally, is this value then globally visible?  var a; function myFunction() {     var a = 4; }  Will other scripts on the page be able to see the value of a being set to 4?

What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?


I have models from an old game called Trespasser that were made on 3ds max back around 1998, and I cant figure out how to see or use them in blender.  I can provide one as a sample if needed, but I would like to see these models, and use them if possible.  Thank you  I do not have 3ds max software, but I also did not realize they had a trial version, so I may do as suggested. I also did not see anything about this in the forum, so I do apologize about the duplicate question.  EDIT : I cannot install  3ds max 2015, for some reason, but assuming it has to do with me using Windows Vista Ultimate instead of 7 or 8. I am looking into other means.  Thank you for the help though, maybe I can figure it out now.

I've tried to import but I don't see the (.max) file as an option when importing. Is there another way to import the 3DMax model into Blender for rigging and animation?


I'm Nigerian, passing through JFK on Delta Air on my way to St. Kitts and Nevis on tourist visa on arrival policy. I want to know if it is possible without a transit visa.

In Europe usually you don't need to go through immigration to change planes (unless you are entering/exiting Schengen). Is it the case in the US as well? May I catch a connecting flight on one of the US airports if I don't have US visa?


When viewing a deleted question that had currently been closed, the close reason(s) and the close voters are no longer displayed. It only shows the deletion action.   (10k only), for instance, was closed before it was deleted, but the reasons for closing are not in evidence. That information is available in the , of course, but that's not easy for mortals to find.  Can the closing information be restored?

Previously - posts that were a mix of closed, deleted or locked use to show at least two of those banners - however, now it only seems to show one.  If a post is closed and deleted (doing a search for closed:1 deleted:1) it only seems to be that the deletion banner is shown while it use to show the close banner and the deletion banner. They're definitely closed according to the timeline and the "reopen" option being available - there's just not the closure reason.  Posts that meet closed:1 deleted:1 locked:1 don't seem to show the lock or close banner... On here for instance the results from closed:1 locked:1 don't look right. Again, according to the timeline, they're definitely closed and locked - just no reason as to why is shown.  It looks to be a network wide thing and not just an SO one.


I have done quite a bit of research on SEO as I have a new website (around 6 months old) and it does not feature on google for any search terms that I would associate with it other than the website name where it ranks 1st lol.  My competitors are all established websites who have been around for a number of years with a solid customer base.  I suppose the main question is... Can i compete? or do i just need to bide my time?  Currently my product page structure has the main headinh <h1> at the top which is the product title  The product description then contains <h2> - Product title and brand and then a description below...  would it make much difference if below the <h2> i added another <h2> containing the product category?  My understanding is that the better googles understanding is of my products, the quicker I can potentially increase my ranking to compete with my competitors?

What are the best ways to improve a site's position in the Google search results?


The gravitational potential energy of an object at a point above the ground is defined as the work done is raising it from the ground to that point against the gravity.  How has this definition been derived? Is this definition derived from the general  definition of potential energy which says - Potential energy is energy which results from position or configuration?  If yes, then how?  Or, has this definition been derived algebraically?

The definition of gravitational potential energy is - The gravitational potential energy of an object at a point above the ground is defined as the work done is raising it from the ground to that point against the gravity . How has this definition been derived?I think this definition has been derived by using the formula Work Done=Force*Displacement . But I don't know how to do this . can someone explain this derivation? Also,  Why can't we define gravitational potential energy like this - The gravitational potential energy can be defined as the amount of work done to lift an object of mass,m to a height,h with acceleration A such that A>g in terms of magnitude? (g=gravitational acceleration)why is this definition wrong?


For a site that carries "lists" of products, what is the best approach to using canonicals? example.com/green-watches.php - this is the MAIN page (by main, it means that this should be indexed in Search results, and this should be the landing page). It will carry list of FIRST 10 products (i.e. first 10 green-watches as listed in the catalog). Now, there can be a total of 55 green-watches in the catalog, so the rest of the pages can have example.com/green-watches.php?list=11 (page2 - having 11th to 20th watch) example.com/green-watches.php?list=21 (page3 - having 21st to 30th watch) and so on.. example.com/green-watches.php?list=51 (page6 - having 51st to 55th watch)  Obviously, the content on each of these pages (main page, as well as page2 to page6) will be different. But I do not want the landing page to be from page 2 to page6....landing should be on the main page only as that's where I wish the site visitor to start. Further, the basic PHP page in all these URLs remains the same - which is example.com/green-watches.php. Its only the argument attached to it ( ?list=11 and ?list=21 and the likes) which are changing. I am catching these arguments in a FORM-GET method. Question - from SEO perspective, do the rest of the pages (page 2 to page 6) need to have their own unique canonical URL, or is it recommended to have their canonicals point to that of the main page? Any other implementation suggestions for above for better SEO?

I know there are similar questions to this, but they either did not cover what I was looking for or I did not understand them fully, therefore I am asking this here.  My situation  At the moment I am using rel prev and rel next as pagination.  <link rel="prev" href="http://www.example.com/category/blablabla/page/2" /> <link rel="next" href="http://www.example.com/category/blablabla/page/4" />   I currently also add a canonical link which refers to the first page, i.e:  <link href="http://www.example.com/category/blablabla" rel="canonical">   The problem  The situation is like this:  The first page has only 20 items (as all other pages do).  With this canonical link i.e to the first page, only the first page gets indexed by Google.  I would like all the pages to get indexed because important content might get lost if they are not indexed.  Should I just change the canonical link to the current URL? i.e the current page, in this case:  <link href="http://www.example.com/category/blablabla/page/3" rel="canonical">   Or should I do something else, if yes, then what would it be?


If I raise a moderator flag pointing out blatant plagiarism, and the OP deletes the post (perhaps because of downvotes, or because someone points out the plagiarism), what happens? Does a moderator still see the flag and take any necessary action on the account (for instance, if it's not the first time the account has been used to plagiarize)?

Currently, when users are putting a custom flag on a post, there is a chance that this flag will be dismissed before a moderator could see it.  For example, if it was a close flag, and the question got closed, all flags about the question are getting removed. Including custom ones. This was , from what I see in similar questions.  The same happens when someone wants to report a spam user, and writes a comment in the flag, about it. If enough people are flagging the post as the basic "it is spam", the answer will get auto-deleted, as well as the flag. This means that it's possible that the moderator will not even see such report of a spammer account, and it makes it harder to actually find them, after, and prevent them from posting new advertisements.  So the request is: is it possible to make it so that custom flags can only be dismissed by moderators?  This would prevent the loss of information that would be given by a user.


I'm on RHEL 7. Security team suggested me to update curl and dbus packages. When I try yum update , it says Loaded plugins: langpacks, product-id, search-disabled-repos, subscription-manager This system is not registered with an entitlement server. You can use subscription-manager to register. No packages marked for update  I verified that the packages are old as mentioned by security team. Below are the screenshots I received from security team.   How can I update the packages as suggested?

I'm new to RHEL. Trying to install software this morning and running into road blocks. Is it required to have a subscription to download packages via yum on RHEL?  I'm coming across different sources on the net, some make it sound like yes, you need a subscription, others making it sound like no, a subscription is only required for support.  In either case I'm stuck unable to install software ATM, because the machines I'm on don't have the subscription registered. Is there a way to install RHEL software without registering a subscription? If so, how?


I have an OL that contains LIs with small inset buttons:  <li id="123">   <button class="action1">Do 1</button>   <button class="action2">Do 2</button> </li>   And my jquery which has set up the functions on document load:  $('.action1').on('click', function() {   // do stuff });   Only, when I'm appending to the list:  li = '<li...' //defines li item here $('#myol').append(li);   The buttons don't do anything. I guess this is because the listeners were attached before the listitem was created, but what is the correct way to attach the listeners to the newly created items (or even better, set them up in such a way that newly created items are accounted for?

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I have a problem in finding the solution of the equation given in the form of:$$153^{197}=x \mod 497$$  Can anyone hep me to solve this question?

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


I have these commands:  find /var/www/html/* -type d -exec chmod 755 {} \; find /var/www/html/* -type f -exec chmod 644 {} \;   I understood from Stephen Kitt's answer  that I could combine them this way:  find /var/www/html/* -exec chmod a-x,a=rX,u+w {} \+   These chmod arguments are less comfortable for me to read, especially in the find syntax (I've yet to become familiar with the nix meaning of the combos like a-x, a=rX, and u+w and I don't have the time and peacefulness of mind to learn it in a serious way in the coming days).  Is it possible to use numbers there? If not, there might be a bit more comfortable way to unite the two commands even if a tiny bit longer than the particular one proposed?

Within my web application directory, how can I change all my folder permissions to rwxr-xr-x (755)? And how can I change all file permissions to rw-r--r-- (644)? I want to change all folders and files including sub-sub files and folders.   I know the following command would change all files and folders but I want to discrimate between a file and a folder.  chmod -R 755 ./my_web_app_project


There is a question in my textbook as follows:     Prove that for a square matrix $A$ to be commutable with any other square matrix $B$ (meaning that $AB=BA$), it is necessary and sufficient for $A$ to be a scalar matrix(i.e., to be of the form $cI$, where $c$ is a scalar and $I$ is the identity matrix).   I have proved the sufficiency part as below:  Given $A=cI$  Then $AB=cIB=cB$ and $BA=cBI=cB$.  Hence, it is proved that $AB=BA$.  But I cannot prove the necessity part, i.e., given $AB=BA$, I cannot prove that $A$ is of the form $cI$.  Please anyone help me solve it. Thanks in advance.

Let $Z_n$ be the set of all $n \times n$ matrices that commute with all $n \times n $ matrices. Show that $$Z_n = \{\lambda I_n \ | \  \lambda \in \mathbb R\}$$  ($I_n$ is the $n \times n$ identity matrix)  I don't know how to use $E_{ij}$ (matrix with $1$ in $(i,j)$ and $0$ elsewhere) and the elementary matrix $P_{ij}$ to prove this question. Can anyone explain it please?


I'm trying to conduct a Student's t-test for a table of values while trying to follow the explanation and details found on . I understand that if the p-value is   <.01 then it's really significant >.05 it's not significant in between then we need more data   But on that page they seem to accept their null hypothesis no matter what the p-value is. So I'm really not understanding now when to accept or reject the null hypothesis.    When you do you accept or reject the null-hypothesis? Is it true that you are never supposed to accept your null hypothesis, but rather reject or fail to reject the null?

Traditional statistical tests, like the two sample t-test, focus on trying to eliminate the hypothesis that there is no difference between a function of two independent samples. Then, we choose a confidence level and say that if the difference of means is beyond the 95% level, we can reject the null hypothesis. If not, we "can't reject the null hypothesis". This seems to imply that we can't accept it either. Does it mean we're not sure if the null hypothesis is true?   Now, I want to design a test where my hypothesis is that a function of two samples is the same (which is the opposite of traditional statistics tests where the hypothesis is that the two samples are different). So, my null hypothesis becomes that the two samples are different. How should I design such a test? Will it be as simple as saying that if the p-value is lesser than 5% we can accept the hypothesis that there is no significant difference?


When a Microbot Alpha has been played, it gives an ongoing action of     [...] All of your minions are considered Microbots.   Does this include minions in your discard pile?  The question came up in a game where a subsequent Microbot Reclaimer was played, which states:     [...] Shuffle any number of Microbots from your discard pile into your deck.   Does this combination allow for reclaiming minions "considered" as Microbots, even when they are in the discard pile as well as from another faction?

Microbot Alpha says "All of your minions are considered Microbots."  Does this mean while this card is in play, every single minion in play and in discard and in my hand are considered Microbots?   For every Microbot Fixer in play, does every single minion I have in play now get +1 because they are all microbots? If Microbot Archive is in play, does every single minion I have now cause me to draw a card when destroyed? If I play Microbot Reclaimer, can I shuffle any minions from my discard pile into my deck (by considering them all microbots)?   It looks like this link addresses the first item above:   And it looks like this link addresses the 3rd item, implying that minions in the discard are not minions because they are out of play:


I have created a split string function and I am getting the desired output. However upon verification in main I can't seem to determine the size of my first dimension to loop over each word in it. here is my code: #include <stdio.h> #include <stdlib.h> #include <string.h>  char **split(char *str) {     int str_length = 0;     int i = 0;     int separator_count = 0;     while (str[i] != '\0') {         if (str[i] == ' ') {             separator_count++;         }         i++;     }      char **word_array;      word_array = malloc((separator_count + 2) * sizeof(char *));        int word_len = 0;     int separator_index = 0;     int b = 0;                                     //to iterate over "str"        for (int a = 0; a < (separator_count + 2); a++) {         word_len = 0;         while (str_length < strlen(str) + 1) {             str_length++;              if (str[b] == ' ' || str[b] == '\0') {                 separator_index = b;                 word_array[a] = malloc(word_len * sizeof(char));                 int word_depth = 0;                 for (int c = (separator_index - word_len); c < separator_index; c++) {                     chrctr = str[c];                     word_array[a][word_depth] = str[c];                     word_depth++;                 }                 word_array[a][word_len] = '\0';         //terminate found and stored word with null charachter                 word_len = 0;                           //reset word length counter to 0                 b++;                                    //skip to next charachter                 break;                                  // break to go to next index of word_array             }             word_len++;             b++;         }     }     word_array[separator_count + 2] = NULL;     return word_array; }  int main() {     char s[] = "A complete toolkit for building search into your product.";  //test string     char **ss = split(s);     for (int i = 0; i < sizeof(ss); i++) {        //here is the problem, and doing sizeof(ss)/sizeof(ss[0])=1 !!         for (int j = 0; j < strlen (ss[i]); j++) {             printf("%c", ss[i][j]);         }         printf ("\n");     } }  I want to verify my output bat can't seem to get the size of the first dimension of my string array I have seen that sizeof(array)/sizeof(array[0]) works, it is not for me it yields 1. and if I replace it with the number of words it works just fine.

First off, here is some code:  int main()  {     int days[] = {1,2,3,4,5};     int *ptr = days;     printf("%u\n", sizeof(days));     printf("%u\n", sizeof(ptr));      return 0; }   Is there a way to find out the size of the array that ptr is pointing to (instead of just giving its size, which is four bytes on a 32-bit system)?


I have a file containing just a certificate and I would like to move this over to a second file and overwrite a line in the file. certificate format will be: -----BEGIN CERTIFICATE----- abc -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- xyz -----END CERTIFICATE-----  The second file is a yaml file and i want to overwrite Value4 with the certificate Value1 Value2 Value3 Value4  Output would be Value1 Value2 Value3 -----BEGIN CERTIFICATE----- abc -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- xyz -----END CERTIFICATE-----  Any ideas on how this can be done?. Ideally I dont want to use line numbers because the second file may have new fields added below the certificate in the future.

I want to write a sed (or awk) command to replace a string from one file with the entire contents of another file. Note that second file from which I want to get the content has more than one line. I tried this:  sed -e "s/PLACEHOLDER/$(sed 's:/:\\/:g' TestOutput.txt)/" SQLInput.txt   but got an error saying sed: -e expression #1, char 22: unterminated 's' command


My problem is the following: I use Mendeley to organize my literature. Conveniently, Mendeley is able to generate BibTex files of my groups, which I reference in my LaTeX document. This allows me to easily add a source to my reference manager, go back to my document and basically cite them immediately.  Now, I added a new source which is a newspaper article. Unfortunately, if I choose "Type: Newspaper Article" in Mendeley, the manager creates a Bibtex entry that looks as follows:  @misc{Doe2019,     author = {Doe, Jane},     booktitle = {NewspaperX},     title = {{Hello There!}},     year = {2019} }   This is the Mendeley Default output and it can't be changed!  This does not include the day or month I could enter in the manager, which is... not good. But, okay. More importantly, if I use Biblatex and bibstyle=authoryear, not even the Newspaper name (booktitle) appears in the bibliography. Here a MWE:  \documentclass[a4paper, 12pt]{article}  \usepackage{filecontents}  \begin{filecontents*}{example.bib}     @misc{Doe2019,         author = {Doe, Jane},         booktitle = {NewspaperX},         title = {{Hello There!}},         year = {2019}     } \end{filecontents*} \usepackage[backend=biber,citestyle=authoryear-icomp,bibstyle=authoryear,uniquename=false]{biblatex} \bibliography{example.bib}  \begin{document}     This is my example \parencite[][]{Doe2019}.     \printbibliography \end{document}   Now, here are my questions:   Is it possible to add the newpaper name to the bibliography by changing the LaTeX-file What would be a suitable workaround?  where one includes a ? Abandonding Mendeley because there are more convenient tools out there?   Edit: Using the Type "Journal Article" in Mendeley at least solves the problem to a certain extent.

I want to cite an online news article, i.e. one that didn't also appear as a printed version, using BibLaTex with the authoryear style. Example:  \documentclass[12pt,paper=a4,bibtotocnumbered,abstract=on]{scrreprt} \usepackage[ngerman]{babel} \usepackage[backend=bibtex,style=authoryear,doi=false,isbn=false]{biblatex} \addbibresource{Export-Test.bib} \DefineBibliographyStrings{german}{     urlseen = {abgerufen am}, }  \begin{document} Test \autocite{Darroch.2017}.  \end{document}   with the corresponding entry in the .bib file:  @Online{Darroch.2017,  author = {Darroch, Gordon},  year = {2017},  title = {Netherlands 'will pay the price' for blocking Turkish visit – Erdoğan },  journal = {The Guardian},  url = {https://www.theguardian.com/world/2017/mar/12/netherlands-will-pay-the-price-for-blocking-turkish-visit-erdogan},  urldate = {2017-03-12} }   The output looks like this:  Darroch, Gordon (2017). Netherlands 'will pay the price' for blocking Turkish visit – Erdoğan URL:  (abgerufen am 12.03.2017)  I've tried multiple things instead of journal, but the name of the news website just doesn't want to appear. In the end, it should look like this:  Darroch, Gordon (2017). Netherlands 'will pay the price' for blocking Turkish visit – Erdoğan In: The Guardian. URL:  (abgerufen am 12.03.2017)  Any ideas how to fix this? Thanks a lot!


I was reading some blog and I found that I can manually start GUI by issuing this command sudo startx, so I did that. I did it in the terminal with the GUI already running. Now I'm unable to login to my user account.   Before that my PC used to boot straight into my account without asking for the password (without even showing the GRUB menu since I have only Ubuntu 12.04 installed on my PC). But now it boots and lands in a screen (without showing the GRUB menu) which displays my user account along with the Guest account. When I choose my account, it asks for the password. I entered the password but it comes back again to the same screen without any response. I am damn sure that the password that I entered was right. When I choose the Guest account, everything goes well. Now I have access only to the Guest account.  Before posting this question, I read similar questions posted here:        and  I tried solutions suggested for them but nothing worked.  This page () and this page () seems to provide some solutions but I could not bring up the GRUB menu by pressing the SHIFT key or the ESC key. While booting, I kept pressing the keys (I tried both the keys separately) but it would land straight onto the screen displaying user accounts.  I logged into the Guest user and changed my administrator account to standard one. I have no way to know what the root password is.   I opened the Terminal in the Guest account and entered sudo passwd root. It returned the following:  sudo: unable to change sudoers gid: Operation not permitted sudo: setresuid() [0, 0, 0] -> [128, -1, -1]: Operation not permitted   Now I can not access any of my files or folders. Are there any possible solutions to my problem without re-installing the OS? Is there any way to reset all the User accounts and regain access to my account?

I need to reset my password. I have followed these steps:    However, then I go to "root" or "netroot" recovery options, it tells me:  Give root password for maintenance (or type Control-D to continue)   Clearly, I do not know the root password. If I type CTRL+D, I return to the list of options. From  I read:  Under chapter 'The Other Way':  4. Highlight the line that begins kernel and press 'e' to edit`   But in the grub configuration file I have no line that starts with kernel. Only:  setparams 'Ubuntu...' recordfail set gxfpayload... insmod part_msdos insmod ext2 set root=... search --no-floppy... linux /boot/vmlinuz-2.6.38... initrd /boot/initrd.img-2.6....   Those are all lines in my GRUB. Which line should I edit? Or is there another way to reset my password?


Almost finished a large interior project and suddenly when ever I open the specific file Blender keeps crashing. I've restarted my MacBook, reinstalled Blende, turned load UI off, then back on again, reinstalled Blender into a different folder. Sent the file to a friends MacBook, duplicated the file then moved it with no luck what so ever. Is there anyway of recovering the file?

When I open a blender file, my project is visible for a few seconds while I can't make any changes to it, and then it closes. Does anyone know how to fix this? This doesn't happen to all of my blender files by the way. I can also start a new project.


I have been riding my bike quite frequently since August 2016. I ride a Roadmaster Granite Peak 26'. Initially, I used to ride continuously for probably 7 miles or 8 miles. I used to clock averages of 12 mph (20 km/h) . Recently, I have started putting more effort into my riding and I clock somewhere between 13.5 mph to 14.5 mph (22-23 km/h). Also, I can definitely do longer distances(i.e. 15-16 miles or 22-24 km at a stretch) on my bike now without getting easily tired and a better average speed.   I wanted to increase my endurance more and would like to go on 20 miles-30 miles (32-50 km) stretch continuously with short breaks.   What are some ways I can achieve this goal?    From

I've just learned of a local century ride that is only 2 weeks away. I'd like to join, but not sure if I'm ready. I've been commuting by bike for the last five years. The last year of my commuting has been 18 miles/day that I do at least 4 days/week. Over the last 2 months, I've done several weekend rides of 40-50 miles, but I haven't gone over 50. I usually take one 10-minute break at about the 75% mark during these longer rides. After these longer rides, I'm tired and hungry, but feel like I could keep going at a leisurely pace after eating. Am I ready to leap to 100 miles? I don't have any days between now and the event where I'll be able to go for more than about a 30-mile ride.  The terrain for the century is flat, just like my normal biking.


How to create a Wi-Fi hotspot (infrastructure network, not ad-hoc) on a Mac without any Internet connection?  In Windows, we can easily create an infrastructure wifi LAN hotspot with:  netsh wlan set hostednetwork mode=allow ssid=MyWifi key=12345678 netsh wlan start hostednetwork   It is compatible with most devices like Android/Windows/Mac/iOS, and it does not require an available Internet connection.  So, is there a similar solution on OS X 10.10 (Yosemite) that:   can create a Wi-Fi hotspot; compatible with most devices; does not require an Internet connection?

Is it possible to put my AirPort in access point mode, so it creates an infrastructure (ie, non-ad-hoc) network from the command line on OS X?  Similar to using System Preferences -> Sharing -> Internet -> Share from … to computers using WiFi.


This is how I have always written event raisers; for example PropertyChanged:      public event PropertyChangedEventHandler PropertyChanged;     private void RaisePropertyChanged(string name)     {         var handler = PropertyChanged;         if (handler != null)             handler(this, new PropertyChangedEventArgs(name));     }   In the latest Visual Studio, however, the light bulb thingamabob suggested simplifying the code to this:      private void RaisePropertyChanged(string name)     {         PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));     }   Although I'm always in favor of simplification, I wanted to be sure this was safe.  In my original code, I assign the handler to a variable to prevent a race condition in which the subscriber could become disposed in between the null check and the invocation.  It seems to me that the new simplified form would suffer this condition, but I wanted to see if anyone could confirm or deny this.

Something that confuses me, but has never caused any problems... the recommended way to dispatch an event is as follows:  public event EventHandler SomeEvent; ... {     ....     if(SomeEvent!=null)SomeEvent(); }   In a multi-threaded environment, how does this code guarantee that another thread will not alter the invocation list of SomeEvent between the check for null and the invocation of the event?


In D7 I would like to display some cause for the 403 and that changes by path (and other factors but those are easy). I can think of a few tricks like using request_uri() to see which page we were on, originally but I wonder if there is a good practice already established for this?

How is it possible for a module to detect when Drupal is outputting the "access denied" page? I know how to do it with Drupal 6; I need to know how to do it with Drupal 7.


I have this string:  Sat Apr 18 23:22:15 PDT 2009   and I want to extract   23   what should I have for it ? something like \d\w

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?


I'm currently working with a couple regexes trying to go through very large chunks of sql to find phone numbers.  The ones I've found are a little too specific, which is causing some problems catching things it shouldn't recognize as phone numbers, mainly coordinates and large numbers.  I'm needing something that strictly looks for 10 and 7 digit phone numbers that are separated by either dashes or periods, nothing else.  Any suggestions out there?

I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:   1-234-567-8901 1-234-567-8901 x1234 1-234-567-8901 ext1234 1 (234) 567-8901 1.234.567.8901 1/234/567/8901 12345678901   I'll answer with my current attempt, but I'm hoping somebody has something better and/or more elegant.


I believe this is another easy one for you LINQ masters out there. Is there any way I can separate a List into several separate lists of Some Object, using the item index as the delimiter of each split?  Let me exemplify: I have a List<T> and I need a List<List<T>> or List<T>[], so that each of these resulting lists will contain a group of 3 items of the original list (sequentially).  example:   Original List: [cat, dog, pane, wolf, pig, sun, queen, fox, x'mas, yak, ice, mark, cold] Resulting lists: [[cat, dog, pane], [wolf, pig, sun], [queen, fox, x'mas], [yak, ice, mark], [cold]]

Is there any way I can separate a List<SomeObject> into several separate lists of SomeObject, using the item index as the delimiter of each split?  Let me exemplify:  I have a List<SomeObject> and I need a List<List<SomeObject>> or List<SomeObject>[], so that each of these resulting lists will contain a group of 3 items of the original list (sequentially).  eg.:   Original List: [a, g, e, w, p, s, q, f, x, y, i, m, c] Resulting lists: [a, g, e], [w, p, s], [q, f, x], [y, i, m], [c]   I'd also need the resulting lists size to be a parameter of this function.


I have this cheat engine script: [Enable] 009516C2: jns 0095138F  [Disable] 009516C2:     je 0095138F  I want to convert it to C++, Can anyone help?

I have a program in which I've lost the C++ source code.  Are there any good C++ decompilers out there?  I've already ran across .


While reading   about 32 bit vs 64  bit OS i came to know that there is instruction length varies from 32 bit to 64 bit.  What actually it means and what is its importance?

What are the differences between 32-bit and 64-bit systems?  If you have used both of them, what kind of sharp differences have you experienced?   Would it be a problem to use 32-bit programs on 64-bit systems in some cases?


Lately, I am having trouble understanding the difference between what is average, what is expected value, and what is mean when using Calculus. I am under the impression now that they are the same thing which confuses me. Why would expected value, the $E[X]$ symbol, have the form $E[X]=\int_a^bx\cdot f(x)dx$, rather than $E[X]=\frac{1}{b-a}\int_a^bf(x)dx$. I thought the second equation was the definition of average from a calculus stand point. I am wanting to know the difference between using these three terms and when to use their corresponding equations appropriately.

For example in statistics we learn that mean = E(x) of a function which is defined as  $$\mu = \int_a^b xf(x) \,dx$$  however in calculus we learn that  $$\mu = \frac {1}{b-a}\int_a^b f(x) \,dx $$    What is the difference between the means in statistics and calculus and why don't they give the same answer?  thank you


I have three questions on Stack Overflow that I want to offer bounties on. Trouble is, I already have an outstanding bounty on another question, and thus I can't offer bounties on any other questions until I award that one (and even then I'll be limited to one at a time). I respectfully disagree with the FAQ's guidance that only one bounty may be offered per user, and request that the limit be increased.

In order to avoid the system being overflown,  at a time was imposed when the new bounty system was introduced, with the plan of looking at this again when some time has passed.   I haven't kept totally close tabs, but I've never seen the overall number of bounties rise above 170 in the past two months. The old average was about 100-150 bounty questions at a time.  In light of this, would relaxation of the rules, as promised, be conceivable? At least to two questions at a time, if not a bit more? If not right now, then at some point in September April?


So I've been starting to make a Cash Register program which will take in what the user is paying and how much the object costs.  This will tell the user how much coins (Toonies, loonies, etc.) they'll get in return.  Here's the part of the code that determines how much coins the user will get in return:  if(amountPayed >= amountToPay) {     remainder = amountPayed - amountToPay;      while(remainder > 0) {          if(remainder >= 2) {             toonies++;             remainder = remainder - 2;             System.out.println(remainder);         }          else if(remainder >= 1) {             loonies++;             remainder = remainder - 1;             System.out.println(remainder);         }          else if(remainder >= 0.25) {             quarters++;             remainder = remainder - 0.25;             System.out.println(remainder);         }          else if(remainder >= 0.1) {             dimes++;             remainder = remainder - 0.1;             System.out.println(remainder);         }          else if(remainder >= 0.05) {             nickels++;             remainder = remainder - 0.05;             System.out.println(remainder);         }          else if(remainder >= 0.01) {             pennies++;             remainder = remainder - 0.01;             System.out.println(remainder);         }      }   I've been having a problem with getting the correct amount, the loop ended up being infinite.  I thought to myself, this can't be true as I made sure that all the values would go through evenly.  I decided I should do some debugging so I made it output the remainder everytime it went through.  Here's what I got:  18.01 16.01 14.010000000000002 12.010000000000002 10.010000000000002 8.010000000000002 6.010000000000002 4.010000000000002 2.0100000000000016 0.010000000000001563 1.5629858518551032E-15   This was very weird to me because the numbers I entered only went to the second decimal.  I was subtracting the numbers from the remainder just fine.  So what's my problem?

public class doublePrecision {     public static void main(String[] args) {          double total = 0;         total += 5.6;         total += 5.8;         System.out.println(total);     } }   The above code prints:  11.399999999999   How would I get this to just print (or be able to use it as) 11.4?


I disassembled a cheap digital tire pressure gauge that had quit working (leaking silver oxide cell, as I discovered).  After deciding it was unrepairable I removed the circuit board, which had the LCD display on the back.  It fell off and seemed to be completely unattached. There was a ribbed rubber strip between a plastic "step" on the the display and the row of contacts.    Here are some images of the LCD:    Front ↑     Back ↑     Edge view showing the "step" ↑     The rubber spacer ↑   I happened to view the display under bright light with a specular reflection from the plastic, and saw this:    Since the ribbing on the spacer runs "vertically" from the contacts on the PCB is that how power and signal are delivered to the faint, almost invisible traces on the display?  I don't see any embedded wires in the rubber... is each rib designed to conduct along its length but be insulated from its neighbors?  The spacer looks and behaves just like a simple piece of rubber.  What is this technology (both the "spacer" and the invisible traces on the LCD) called?

The LCD below is from a cheap digital clock which was (obviously) damaged (broken glass).    The electrical connection between the PCB and the display was realized with this pink strip.    Its flexible...    ...and consists of alternating rows of conductive and insulating material between the pink boarders.    [above image was altered in contrast/brightness to highlight the alternating strips]  What is this kind of connector called? Is it only used for displays?   I am pretty impressed that the connection is reliable just from the very slight pressure between the strip and the PCB. Also, its easily removable from the display. There seems to be some conductive layer on the glass, from where the signal goes into the displays internals. This connection seems to be damaged for the three rightmost signals, where the glass is broken.


I am currently making a memory game where it spawns a 3D object into the scene and checks if the 2 game object is the same. So currently, my scripts is able to do the checking by using the name of the gameobject and able to spawn the amount of gameobject based on the amount of textures/material that is in the list but I have run into a problem where 3 or more of the same texture of the gameobject have spawn, which I was thinking of using Boolean to limit the amount of gameobject being spawn with the same texture, but I do not know how I should implement it into the code. By the way, with the current code, the gameobject spawns at the same location which I have not got into, as I was stuck due to having the current issue. public class CardControl : MonoBehaviour { public List<Material> materialList; public GameObject prefab; private Vector3 pos; private Quaternion rot = Quaternion.identity; private bool Same;  private float XPosition = 0f; private float YPosition = 0f; private float ZPosition = 0f;  private void Awake() {     pos = new Vector3(XPosition, YPosition, ZPosition);     Same = false;       for (int i = 0; i < (materialList.Count * 2); i++)     {         Material mat = RandomMaterial(materialList);                  InstantiateWithMaterial(prefab, pos, rot, mat);              } }  public Material RandomMaterial(List<Material>_List_) {      return _List_[Random.Range(0, _List_.Count)];      }  public void InstantiateWithMaterial(GameObject _prefab_, Vector3 _pos_, Quaternion _rot_, Material _mat_) {     GameObject obj_ = Instantiate(_prefab_, _pos_, _rot_);     obj_.gameObject.GetComponent<MeshRenderer>().material = _mat_;     obj_.name = _mat_.name + "1"; } }

What is the best way to randomize the order of a generic list in C#? I've got a finite set of 75 numbers in a list I would like to assign a random order to, in order to draw them for a lottery type application.


Let $G$ be a group and $\psi_a:G\rightarrow G,a\in G,\psi_a(g)=aga^{-1}$, I need to show that $\psi_a$ is homomorphism one to one and onto  It's not the same question like      "Is the conjugation map always an isomorphism?"   because here I need to show why $\psi_a$ is one to one and onto  Attempt:  $\psi_a(g_1g_2)=ag_1g_2a^{-1}$  $\psi_a(g_1)\psi_a(g_2)=ag_1a^{-1}ag_2a^{-1}=ag_1g_2a^{-1}$  $ \Rightarrow \psi_a $ is hom'

Given a group $G$ with $a\in G$ fixed, define $\phi: G \to G$ by $\phi(x) = axa^{-1},  x \in G$, I am wondering when $\phi$ is an isomorphism. I think that it is always an isomorphism because it is one to one, and the order of the domain ($|G|$) and the order of the range are equal. Am I wrong in thinking this?


I have uninstalled ubuntu but the bootstrap is still showing ubuntu before starting what to do?

I have a computer that dual-boots (or tri-boots) Windows 8 Release Preview, Windows 7, and Ubuntu 12.04. Grub boots between Windows 8 and Ubuntu; for which I use primarily. Recently, I decided to remove Ubuntu, as I hardly used it. I deleted the Ubuntu partition accidentally before replacing the Grub bootloader. Now, whenever I want to boot the machine, it gives me the "grub-rescue" prompt -- I am unable to boot into either Windows (8 nor 7), nor Ubuntu (except via USB, of course). I do not have any Windows 7/8 recovery media, so that isn't an option. Please note that after I deleted the Ubuntu partition, I put the PC into hibernate, and then turned it on. This means the C:\ [Windows 8] drive cannot be mounted. I don't know if that is bad, but it definitely doesn't make things better.  I am currently booting Ubuntu via USB, in an effort to restore the Windows bootloader. I have looked into using boot-repair to solve the problem using the instructions , although after attempting to apply the changes, it gave the error: "Please install the [mbr] packages. Then try again." I don't know why I'm getting this error; is there a way to install the 'mbr packages?' I honestly don't know what exactly they are, nor how to install them. Are there any other options I have not yet exhausted to be able to boot back into Windows, in the case that there is a better way? I want to set the bootloader to boot into Windows 8, but booting into either Windows 7 or 8 is fine (I can use EasyBCD from there). Is there a simple solution to this? I've checked BIOS, and I haven't been able to find a way to boot into Windows.


I take a lot of pictures of my sons playing High school baseball (and at times lacrosse and soccer). And a lot of my sons' travel baseball games.  I have a Canon Rebel EOS XSi (450D) which of course came with a Canon  EF-S 18-55mm lens.   I needed a zoom lens and my father recommended a 75-300mm lens. Which I realized too late didn’t have stabilization.  My pictures are blurry. The pictures at night are even worse. I am desperate to get a zoom lens that will work for high school baseball and travel baseball and within two years some college baseball pictures.  Help! What type of zoom lens will get me through? And is there a lens that  will work with low light or at night games?  Is my a bit older Canon Rebel EOS XSi (450D) even fast enough to handle these type of pictures with this type of lens?  I have tried to figure this out and haven’t been successful. Is there another option than the EF 70-200 f/2.8L? Would the 75-300mm with a stabilizer help at all?

I recently took on my first paying client, and she is also into photgraphy. She usually does sports for her highschool yearbook. They just have an entry level Canon DSLR with a kit zoom on it that goes up to 200mm, but it's not very fast (f/4 or 5.6 or so). She told me that she has a tough time - especially at basketball games - getting shots with any kind of reasonable lighting, and has to do a lot of work in post just to get them reasonable.   mentions the Cannon EF 300mm f/2.8L IS USM II for professional sports photographers. At $6k USD I suspect the yearbook won't be springing for that lens anytime soon.  So I was curious, are there any reasonable quality, fast lenses for Canon cameras that are lower priced (certainly no more than say, $1k)? I'd love to be able to point them to a couple of options. I assume the largest print they'd be making would be a full spread in the yearbook - maybe two 17"x11" (two 8.5" side by side)


What will be the sign convention for radius of curvature of a concavo-convex lens ? I know for equibiconcave and equibiconvex separately but for mixed one I am not clear  .  For example for the following what will be the sign convention for radius of curvature here:

Why is the sign convention used in the derivation of the lens formula and yet used again when it is applied in numerical problems? Won't the whole idea of sign convention be eliminated if it is used twice?


Probably this is very naive question, based on lack of understanding but I was watching a video from Andreas M. Antonopoulos about blockchain, bitcoin and consensus algorithms and he asked for the SHA-256 output of the string Hello!. A guy told him the first few characters, and being Windows/C# dev I decided just for fun to check the answer implementing this very simple C# method:      public byte[] Generate(string valueToHash)     {         byte[] hashValue;         byte[] stringToBytes = Encoding.ASCII.GetBytes(valueToHash);          using (SHA256 hashGenerator = SHA256.Create())         {             hashValue = hashGenerator.ComputeHash(stringToBytes);         }          return hashValue;     }   and then output the result using this method:      public static void PrintByteArray(byte[] array)     {         for (int i = 0; i < array.Length; i++)         {             Console.Write($"{array[i]:X2}");             if ((i % 4) == 3) Console.Write(" ");         }         Console.WriteLine();     }   But I got a different result.   I remember in the past that there were sites which were storing a huge databases of hashes and the actual value to produce them and back then it was possible to paste the hash value and if it's something common you will get the actual string. This got me to think that no matter what language/Os you are using, a value hashed with SHA-256 for example would produce the same result. However it seems that this is not entirely the case. The guy from the video who provided the answer turned out (from the comments) to use a Mac machine, so what exactly is causing the SHA-256 to produce different outputs for the same input? Is it the OS, is it the programming language? Maybe I've made mistake in my simple code?

If you hash a string using SHA-256 on your computer, and I hash the same string using SHA-256 on my computer, will we generate the same value? Does the algorithm depend on a seed (so we'd both need the same seed) or some other such parameter?  edit:  To clarify, by 'string' I meant 'the same byte input', which as the comments and @ispiro's answer point out, may be different for the same character string depending on the encoding.


We need to convert the following to reported speech:     Why have you taken a room on the tenth floor?   I am confused about the word order.  Should it be     He asked her why she had taken a room on the tenth floor.    or     He asked her why had she taken a room on the tenth floor.   or neither? Why?  I suppose since we convert an interrogative sentence into a declarative one (on conversion to reported speech), the correct one would be the first. However, the it doesn't 'sound' right. And English is not lacking in exceptions.

I believe the sentence in the title is grammatically correct.   Recently I've seen too many people writing it this way:     I'm not sure what is the right way.   Is it grammatically correct as well? Maybe in a different sense? Or simply misuse by non-native speakers?


When studying the irreducible representations of SO(3) one usually looks at the irreps of the infinitesimal rotations instead, i.e. the ones of so(3), the Lie Algebra of SO(3). The Irreps of so(3) can be parametrized by a single number $j \in {0, 1/2, 1, 3/2, ...}$  These irreps of so(3) can be raised to irreps of SO(3), via the map that maps elements of so(3) to SO(3).   My question now is: How does SU(2) come into play? IIRC the irreps of SO(3) only correspond to the full-integer irreps of so(3). How is this possible when every so(3) irrep can get raised to one of SO(3) as described above? Do several irreps of so(3) get raised to a single one of SO(3)?  If what I said so far is correct, then the discovery of the Zeeman effect called for an enhancement of this theory, as some spectral lines showed a degeneracy of $2j + 1 \in N$, meaning j had to be a half-integer: only the full integer irreps of SO(3) aren't enough!  SO(3) and SU(2) are isomorphic to each other, up to the Rotations $\pm id$. How does this solve the issue of SO(3) not accounting for half-integer representations?  Cheers and thanks in advance!

$SU(2)$ is the covering group of $SO(3)$. What does it mean and does it have a physical consequence?  I heard that this fact is related to the description of bosons and fermions. But how does it follow from the fact that $SU(2)$ is the double cover of $SO(3)$?


I enjoy reviewing on SO, is it currently possible to review on the iOS app? If not, is it planned to be implemented?

I'm using the official Stack Exchange mobile app for iOS or Android, and  My app crashed! It doesn't look good on my new smartphone. It won't run after I updated my device. I noticed another bug. I have an idea for a new feature which is currently not in the app.  How do I report bugs with or request features for the iOS and Android apps? Also:  I've used the built-in functionality of the app to report a bug or submit a feature request. Did I do the right thing? The app prompted me to post on Meta after an error occurred. Should I post about it here? I'm wondering why the latest version is from 2017. I've heard rumors that the apps are no longer supported; is that true? I can't find the app on my device's app store anymore! Where did it go?     We get a lot of bug reports from users about the mobile apps, which are unsupported, and at the moment, there is no centralized Q&A pair for those to be closed as duplicates of (the relevant answers are spread across multiple unrelated questions). This question is an FAQ proposal, to serve as a directly-related duplicate target for those questions.


Related:   I am in Ukraine I have 70 days left on my shengen visa My 180 day period ends in 40 days I want to travel to Spain for as long as possible If I travel to spain right now, how long can I stay there? 40 days? Or 70 days? Or Do I have to take a plane home in 40 days and then a plane to Spain the next day to enjoy 90 more days? Seems nonsensical, right?     quotes      The 6 month (or 180 days to be precise) period starts on the day of   the first entry into the Schengen zone (Note that the day of first   entry means the day you physically arrive in the zone and not the day   the validity of the visa starts). In that 6 month period, you can only   stay in the Schengen zone for a maximum of 90 days, irrespective of   whether you have a new Schengen visa issued by the same or a different   Schengen country that is valid beyond this 6 month period. At the end   of this 6 month period, a NEW 6 month period starts and you can again   spend a maximum of 90 days in the Schengen zone, provided you have a   valid visa. If your stay duration overlaps two 6 month periods, then   you must individually satisfy the 90 day limit in BOTH periods. All   following 6 months period will be calculated back to back from the   date of the first entry, until you remain outside the Schengen zone   for at least 6 months. When you stay outside for at least 6 months   (continuously) and THEN enter the Schengen zone, the six month period   again starts from the day of the entry. It would be as if you were   entering the Schengen zone for the first time.   What does the "you must individually satisfy the 90 day limit in BOTH periods" actually mean? Does it mean that I must be 90 days in one and 90 days max in other visa, or 90 days in both visas combined or what?  But the link is not clear enough for me to understand.  I even read the  and used it's calculator, which seems to give off random numbers.  How am I supposed to follow the rules if no one seems to know them.  Edit: There is no such thing as a period overlap, it's just that you can't stay for more than 90 days in the last 180 days, that's the only rule.

I have searched the web a lot and could not find an answer that fits my situation. Here are two links that are quite contradictory:       My situation:  I've visited Portugal in December 2012 for 29 days on a Schengen visa valid from December 1st, 2012 to February 1st, 2013 for research purposes (I am a Ph.D. student). I want to visit Sweden from February 10th, 2013 to May 10th, 2013 (89 days). I have applied for a Schengen visa again (for research). How will the 90/180 rule work in my situation?


Is the word "lettuce" an uncountable noun or countable noun ?

As a non-native English speaker, I have a bit of trouble finding the plural of the word 'lettuce'. In my own language (Dutch) it doesn't have a plural at all, and 'lettuces' simply sounds funny to me. Is that just a feeling, or is this word actually not really being used? Would there be another way of expressing the same thing (i.e. bunches/pieces of lettuce), what would be the word of quantity for lettuce?


I (Indonesian) have a possible travel itinerary from Japan to Berlin via UK Heathrow airport. From the airline website it says that I need to move from Terminal 3 (arrival from Japan) to Terminal 5 of Heathrow airport. As I have never been to Heathrow before, do I need to pass the border check/immigration? If so then  do I need to have UK transit visa or some sort? I have residence permit visa for Germany.

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


I'm moving from the UK to Australia later this year, and shipping most of my stuff, including two bicycles (simply hybrid bikes, nothing fancy).  Australia has strict biosecurity rules about what you can bring into the country, including cleaning requirements for things like bikes. They want to avoid you bringing in any foreign seeds or bugs that could cause problems.  I have a cheap power washer that would certainly do a good job of cleaning the bikes, but I'm concerned that it could blast water into bearings and whatnot, potentially causing issues.  What do you recommend?

I was chatting to the guys at my LBS the other day about how they get my bike so clean when I take it in for a service. They said they use compressed air to clean it.   They warned I shouldn't use any high pressure water because it can get into the sealed bearings and cause damage. I also noted on the  (right at the end) that you should "Never spray your bicycle with water under pressure".  How much of an issue is this? Rinsing the bike with the hose is such a convenient way to wash off loose grit and then the soap after washing. How do you clean your bikes?