I have this command (KSH)  find &lt;path&gt; -regextype posix-extended -type f -regex '.*/txt' -exec ls -l --full-time \{\} \; | sort -bnr   So, I'm reading and deciphering the command above so far what I know is that   -regextype posix-extended   this just changes the regextype to posix-extended  -type f   this only return files  -regex '.*/txt'   this is just regular expression  -exec ls -l --full-time   executes ls -l --full-time  \\{\\}   this one I don't get. What does it do? What I know is that I need to end -exec with {} \; but why there's backslash inside the curly braces?
Examples  I've recently found examples of using pairs of enclosing braces {}, with nothing in between the opening and closing braces, as arguments to commands and even to their options:  cat foo | xargs -I{} echo {}  find . -size 0 -exec rm -i {} \;  No Documentation  My problem is that I cannot find a documentation in the  that describes the usage of {} in such context as in the examples above.  I do not think it is a , because a dollar sign must precede the enclosing braces in a parameter expansion as in ${}.  It cannot be a  either, because it takes the form of {x..y[..incr]}, where x and y are not optional.  It also cannot be a  either, because {} is used as arguments.  Questions   What does a pair of enclosing braces {} even mean, in general, as an argument to any command that accepts it? Where can I find a documentation that describes the usage of {} as arguments?
I gave my friend  as a brainteaser; while her attempted solution didn't work, it raised an interesting question.  I flip a fair coin repeatedly and record the results.  I stop as soon as the number of heads is equal to twice the number of tails (for example, I will stop after seeing HHT or THTHHH or TTTHHHHHH).  What's the probability that I never stop?  I've tried to just compute the answer directly, but the terms got ugly pretty quickly.  I'm hoping for a hint towards a slick solution, but I will keep trying to brute force an answer in the meantime. Exam with 18pt main font Replacing strings in files based on certain search criteria is a very common task. How can I    replace string foo with bar in all files in the current directory? do the same recursively for sub directories? replace only if the file name matches another string? replace only if the string is found in a certain context? replace if the string is on a certain line number? replace multiple strings with the same replacement replace multiple strings with different replacements Why do we let hostile users dictate the perception of Stack Overflow? I am having some issues when rendering an image, my rendering screen is turning into grey even when making a full render. What am I doing wrong? How to print every Nth character of a string? This line of code does exactly this except I want it to start at the first character not the 7th. $ echo 1234567890abcdefghijklmnopqrstuvwxy | sed 's/.\{1,7\}\(.\{0,1\}\)/\1/g'  What I'm looking for is 19gow HUD is not working after upgrade My HUD is not working after I upgraded from 11.04 (and or 11.10).  It prompts for command and it tries loading for 4 seconds then gives up. What was L's real name? I watched through Death Note once, and I never remember hearing L's name, even after he died.  What was L's real name, or did he never have one (it was never said)? What causes a force field to be "non-conservative?" What does unwrapping a model do and why is it important? On Ubuntu 18.04, I have connected my laptop to an external display and I am able to set the external display as primary and external display only mode. But when I turn on my laptop or log out from my session the display login screen is displayed only on my(internal) laptop screen. But once I login the display switches to external only and my laptop screen turns off as expected. Is there a way I can make the login screen appear only on the external screen on bootup or on logout as in 16.04? Also the login screen does not follow my cursor as in 16.04. Analogue of closed graph theorem This is the analogue of closed graph theorem for compact space          Suppose that $X$ and $K$ are metric spaces, that $K$ is compact, and that the graph of $f: X \rightarrow K$ is a closed subset of $X \times K$. Prove that $f$ is continuous.      Because metric space is first countable, all we need is to prove that if $x = \lim_{n \rightarrow \infty} x_{n}$, then $f(x) = \lim_{n \rightarrow \infty} f(x_{n})$. Suppose $x = \lim_{n \rightarrow \infty} x_{n}$, then because $K$ is compact, sequence $\{f(x_{n})\}$ has a subsequence $\{f(x_{n_{i}})\}$ converge. Because the graph of $f$ is closed, we must have $\lim_{n \rightarrow \infty}\{f(x_{n_{i}})\} = f(x)$. All we need to prove now is $\{f(x_{n})\}$ converge to $f(x)$, but I can't prove that. Can any one help me. I really appreciate. Thanks Did Voldemort die or stay in limbo after the final battle? In Harry Potter and the Deathly Hallows, while Harry is in Kings Cross he sees something like a small child, which is the fragment of Voldemort's soul that was attached to him.     He recoiled. He had spotted the thing that was making the noise. It had   the form of a small, naked child, curled on the ground, its skin raw and rough, flayed-looking, and it lay shuddering under a seat where it had been left, unwanted, stuffed out of sight, struggling for breath.      He was afraid of it. Small and fragile and wounded though it was, he did not want to approach it. Nevertheless he drew slowly nearer, ready to jump back at any moment. Soon he stood near enough to touch it, yet he could not bring himself to do it. He felt like a coward. He ought to comfort it, but it repulsed him.      Harry Potter and The Deathly Hallows   Once Harry returns to the world of the living, that part of Voldemort's soul stays in limbo. Is this what happens to all fragments of someone's soul if he has divided his soul by creating a Horcrux? Does that mean that Voldemort's soul however crippled will stay in limbo or when all parts of his soul die, so does he? Cardinal number subtraction We all know that $|\mathbb{N}| = \aleph_0$. Since $|\{-1\} \cup \mathbb{N}| = \aleph_0$ as well, I guess you could say that $\aleph_0 + 1 = \aleph_0$.  You can go on to derive that $\aleph_0 + \aleph_0 = \aleph_0$, and by induction $n \times \aleph_0 = \aleph_0$ (assuming that $n$ is finite, anyway).  Now, here's a thing: What is $\aleph_0 - \aleph_0$?  Well, $|\mathbb{P}| = \aleph_0$, and $|\mathbb{P} \backslash \mathbb{N}| = \aleph_0$, so perhaps $\aleph_0 - \aleph_0 = \aleph_0$?  No, wait. Consider the set $S = \{n \in \mathbb{N}: n &gt; 5\}$. Now we have $|S| = \aleph_0$, and yet $|\mathbb{N} \backslash S| = 5$. So maybe $\aleph_0 - \aleph_0 = 5$?  But that is absurd, since we can redefine $S$ to make the result any finite number we wish. Or we can define $S$ such that the result is countably infinite.  Does this mean that the notion of $\aleph_0 - \aleph_0$ simply has no definite answer? Or am I just being too simplistic here? How do I use Moq to mock an extension method? I am writing a test that depends on the results of an extension method but I don't want a future failure of that extension method to ever break this test. Mocking that result seemed the obvious choice but Moq doesn't seem to offer a way to override a static method (a requirement for an extension method). There is a similar idea with Moq.Protected and Moq.Stub, but they don't seem to offer anything for this scenario. Am I missing something or should I be going about this a different way?  Here is a trivial example that fails with the usual "Invalid expectation on a non-overridable member". This is a bad example of needing to mock an extension method, but it should do.  public class SomeType {     int Id { get; set; } }  var ListMock = new Mock&lt;List&lt;SomeType&gt;&gt;(); ListMock.Expect(l =&gt; l.FirstOrDefault(st =&gt; st.Id == 5))         .Returns(new SomeType { Id = 5 });   As for any TypeMock junkies that might suggest I use Isolator instead: I appreciate the effort since it looks like TypeMock could do the job blindfolded and inebriated, but our budget isn't increasing any time soon. Why is the complex number $z=a+bi$ equivalent to the matrix form $\left(\begin{smallmatrix}a &-b\\b&a\end{smallmatrix}\right)$ Possible Duplicate:          On Wikipedia, it says that:     Matrix representation of complex numbers   Complex numbers $z=a+ib$ can also be represented by $2\times2$ matrices that have the following form: $$\pmatrix{a&amp;-b\\b&amp;a}$$   I don't understand why they can be represented by these matrices or where these matrices come from. Determining the characteristic of a field If $\mathbb{F}=\{ 0,1,x,y\}$ is a field with four elements, why is the characteristic 2?   In a field with four elements, the characteristic is 2 or 3(since it has to be a prime). Is there any way to determine precisely the characteristic of this field, and in general any finite field? What books, journals, and/or electronic resources have you found most valuable for expanding your knowledge in the GIS field, and why? How can I correct a reviewer's opinion? My edit to an answer was accepted by two of the three reviewers, with the third rejecting with a claim that part of my edit was incorrect.  In fact, my proposed edit was entirely and demonstrably correct, and the reason given for rejecting is invalid.  How can I let that reviewer know about their error, and have them change their review to "Accept" - changing stats for both of us?  Please note:  This is not the same question as asking for an appeal of an edit that was rejected.  It's asking what I can do about one of the three reviewers, a dissenter who voted against my edit based on their incorrect information. I'm having some trouble proving the following statement using mathematical induction:   $$\frac{1}{2}n^{\frac{3}{2}} \leq \sqrt{1} + \sqrt{2} + \sqrt{3} + \sqrt{4} + ... + \sqrt{n}      ,\text{ (for all sufficiently large n)}$$   I'm sort of confused because $n^{\frac{3}{2}}$ = $n  n^{\frac{1}{2}}$ which means that there are n of the largest possible root values on the left hand side while the right hand side has values like $\sqrt{1}$, $\sqrt{2}$, etc. As n grows sufficiently large wouldn't the left hand side outgrow the right hand side no matter what the constant multiple is? If I'm thinking about this correctly just let me know, if not, any help would be appreciated.