What does the '|' (vertical bar) character mean in a Terminal command? Example: In a Terminal command xdpyinfo | grep resolution (that I have taken from an answer), does the | character mean that the xdpyinfo output shall be sent to the grep program input for printing a line containing the resolution string? Where should I seek for such an information to avoid filling this forum by too simple questions? Thanks.
What is the difference between "Redirection" and "Pipe"? This question may sound a bit stupid, but I can not really see the difference between redirection and pipes.  Redirection is used to redirect the stdout/stdin/stderr, e.g. ls &gt; log.txt.  Pipes are used to give the output of a command as input to another command, e.g. ls | grep file.txt.  But why are there two operators for the same thing?  Why not just write ls &gt; grep to pass the output through, isn't this just a kind of redirection also? What I am missing?
What differences exist between third-party and official lenses for Canon APS-C DSLRs? I am just another guy who just taken up photography as a social hobby who enjoys taking pics of everyday life, social events / parties &amp; some portraits. Need camera for short overseas trip (2-3 times a year), maybe some landscape pics.   I have done some research and have come up a list of main lenses that I am considering and hope you guys can offer some advice / comments to whether I should make those purchases.   Main reason why I chose "third party lenses" 'cos apparently they cost less, newer and are "award winning" - so I don't see the point of spending more for the original canon lens (which some maybe quite old - ie 3-5 yrs).   Sigma 17-70mm F2.8-4 DC MACRO OS HSM Lens (day to day lens) Sigma 85mm F1.4 EX DG HSM (for portrait &amp; bokeh effects) Wide angle lens (any suggestions)   Main questions / comments please...   Q1) What do you think of the lens choices that I have decided to build my kit?  Q2) Any wide angle lens that you will recommend? (third party or canon) or should I get wide angle zoom lens ? Q3) What are your thoughts that I chose all my lens from Third Party instead of Official Canon ones... is that a "smart move"? I would like to know what would be the best way to do unit testing of a servlet.   Testing internal methods is not a problem as long as they don't refer to the servlet context, but what about testing the doGet/doPost methods as well as the internal method that refer to the context or make use of session parameters?  Is there a way to do this simply using classical tools such as JUnit, or preferrably TestNG? Did I need to embed a tomcat server or something like that? How does "failure" work in Dungeon World? How does it move the story forward? I am having trouble understanding the specifics of failure in Dungeon World. According to the rules, a GM should "make a move" against players when they fail, and that's alright, I get that.  What I don't get is how a GM is supposed to advance the plot by doing so. Let's take an example:  Rick the Fighter is climbing a massive chain that serves to hold down the wizards tower, preventing it from drifting off. He makes the move Defy Danger, to avoid slipping of, since it's raining hard, and the chain is slippery with algae and moss. He rolls and get a score of 5, meaning he fails.  In the above situation, he fails climbing the chain, so the GM should make a move. I have a hard time seeing what move would advance the story here, since I feel that the failure would imply that he doesn't get to the tower.  Is this one of those situations, where you just skip making a roll, and just let the players climb the chain, or does anyone have any idea how to handle the move, so that the story is advanced somehow?  I just want to be able to give the players some dangers that aren't traps and monsters, and I thought that a flying wizards tower was cool. I'm having a hard time seeing how I can advance the story on a failure in this situation.    Let me elaborate on the problem. I will not say that it's wrong to make the players succeed with some "cost", even on a failed roll, it just makes true "failure" impossible. That's my beef about it. The players will eventually succeed at anything that doesn't outright kill them. How can I look at my character? Is there a way I can inspect my character's face at any point in the game after creating it during the bathroom scene?  I am playing on PlayStation 4 and rotating with the right stick in 3rd-person view obviously does not show the face. I haven't found any mirrors or shiny objects to use the reflection either.  The reason for this is that I forgot what she looks like and also I want to share my monstrous creation with others but I have already left the vault! Let G be a finitely generated abelian group and M a compact manifold,  I want to prove that $H_r(M,G)$ is finitely generated for $r\ge 0 $.  First I was thinking if  I could do induction over $r$ because for $r=0$, $H_0(M,G) \cong \bigoplus_{i=1}^nG$ where $n$ denotes the number of connected components of M.But for $r&gt;0$ I can't see a way to relate $H_r(M,G$) and $H_{r+1}(M,G)$.  Then I tried to use the fact that for every compact surface there exists a finite cover $\{A_i\}_{i=1}^m$ such that the finite intersections of $A_i$'s are contractile.Let $\{A_i\}_{i=1}^m$ such cover for $M$.Then,using induction on $m$, we have :  -For $m=0$, $M$ is contractile and $G$ finitely generated then $H_r(M,G) $is finitely generated.  -For $m=r$ it's true by induction hypothesis.  -For $m=r+1$ now putting $A_{r+1}=B$ and $\cup_{i=1}^r A_i=A$, and using Mayer Vietoris we get:  $$ ...\rightarrow H_{r+1}(A\cap B,G)\rightarrow  H_{r+1}(A,G) \oplus H_{r+1}(B,G) \rightarrow H_{r+1}(M,G)\rightarrow H_{r}(A\cap B,G) \rightarrow...$$   Here I don't know what to do, maybe I'm missing some algebraic argument It's easy to see that $H_{r+1}(A\cap B,G)$ and $H_{r+1}(A,G) \oplus H_{r+1}(B,G)$ are finitely generated.But how can I argue that $H_{r+1}(M,G)$ is finitely generated? Any idea would be aprecciated. How do I connect the initial highway to my six-lane road? permission reporting on sudoers I'm looking for a good, consistent and easy way to do a report of sudoers permissions for every user and group on the system. For users, I want the report to include permissions granted via group membership. Profile picture cannot have transparent background Collapsing a stream of multiple lines into one line I have a file containing a a large number of lines, each of which contains a bunch of numbers which are separated by spaces. I process this data in a pipe in some way, and then I want to collapse the multiple lines into a single line of all the numbers separated by spaces.  Is there a standard command-line utility I can use to do this? It seems like most line-by-line utilities won't mess with the newlines... How can I create an AddIn to ArcGIS Pro and where can I find it from ArcGIS Pro application? OpenSource ATI driver - Fan running at full speed all the time I know this is a common problem and have read other topics but couldn't resolve. Anyways yesterday I found a solution - I have 2 graphic cards (hybrid) and they were both on. So I turned one off and installed Jupiter for power management and from there on the fans were quiet and I was happy as hell.  However (:)), yesterday evening I also updated the system and the fan and it's noise came back. I checked whether I am using only 1 graphics card and I am.  c0dehunter@mintBox ~ $ sudo lshw -c video [sudo] password for c0dehunter:    *-display                       description: VGA compatible controller        product: RS780M/RS780MN [Mobility Radeon HD 3200 Graphics]        vendor: Hynix Semiconductor (Hyundai Electronics)        physical id: 5        bus info: pci@0000:01:05.0        version: 00        width: 32 bits        clock: 33MHz        capabilities: pm msi vga_controller bus_master cap_list rom        configuration: driver=radeon latency=0        resources: irq:18 memory:c0000000-cfffffff ioport:c000(size=256) memory:fbcf0000-fbcfffff memory:fbb00000-fbbfffff   Maybe the problem is (false) temp reading from GPU?  c0dehunter@mintBox ~ $ sensors acpitz-virtual-0 Adapter: Virtual device temp1:        +44.0°C  (crit = +105.0°C)  k10temp-pci-00c3 Adapter: PCI adapter temp1:        +47.0°C  (high = +70.0°C)                        (crit = +115.0°C, hyst = +110.0°C)  radeon-pci-0200 Adapter: PCI adapter temp1:       +127.5°C     The thing that is weird is that if I boot into Windows the fan is still at full power (previously it wasn't). Did I f--- up my hardware with software? :)  //OH, yes - I forgot to mention that my laptop is not hot at all. The temps are about 50°C. How to add startup applications in lubuntu? Is there a 'Startup applications' app for lubuntu? Or how do I add apps to startup? I attempted a tutorial to add entries to ~/.config/autostart, but it did not work. Isn't there an easy way? Any ideas please? Move partition data with dd to the right Stack Exchange sites need a universal clock that is visible! Since the Stack Exchange sites run on one clock, and a clock that is not common to most of us (such as those of us in the US), can we display a clock with the site time (UTC) displayed somewhere on every page, such as at the bottom with the other text?  That way we are more aware of when the days turn over, and ecetera...  close votes, delete votes, flags, and normal votes would also benefit from this as well (thanks @Grace Note!)...    What do you guys think? yea or nay? thoughts? Checking the way to stop duplicate names - validation rules or triggers This is a recurring question (see ,  and ), but I have a different spin.  Suppose I have a bunch of samples from a generic MCMC sampler. For each sample $\theta$, I know the value of the log likelihood $\log f(\textbf{x} | \theta)$ and of the log prior $\log f(\theta)$. If it helps, I also know the value of the log likelihood per data point, $\log f(x_i | \theta)$ (this information helps with certain methods, such as WAIC and PSIS-LOO).  I want to obtain a (crude) estimate of the marginal likelihood, just with the samples that I have, and possibly a few other function evaluations (but without rerunning an ad hoc MCMC).  First of all, let's clear the table. We all know that the harmonic estimator is the . Let's move on. If you are doing Gibbs sampling with priors and posteriors in closed form, you can use ; but I am not sure how to generalize outside of those cases. There are also methods that require you to modify the sampling procedure (such as via ), but I am not interested in that here.  The approach I am thinking of consists of approximating the underlying distribution with a parametric (or nonparametric) shape $g(\theta)$, and then figuring out the normalization constant $Z$ as a 1-D optimization problem (i.e., the $Z$ that minimizes some error between $Z g(\theta)$ and $f(\textbf{x}|\theta) f(\theta)$, evaluated on the samples). In the simplest case, suppose that the posterior is roughly multivariate normal, I can fit $g(\theta)$ as a multivariate normal and get something similar to a Laplace approximation (I might want to use a few additional function evaluations to refine the position of the mode). However, I could use as $g(\theta)$ a more flexible family such as a variational mixture of multivariate $t$ distributions.  I appreciate that this method works only if $Z g(\theta)$ is a reasonable approximation to $f(\textbf{x}|\theta) f(\theta)$, but any reason or cautionary tale of why it would be very unwise to do it? Any reading that you would recommend?  The fully nonparametric approach uses some nonparametric family, such as a Gaussian process (GP), to approximate $\log f(\textbf{x}|\theta) + \log f(\theta)$ (or some other nonlinear transformation thereof, such as the square root), and  to implicitly integrate over the underlying target (see  and ). This seems to be an interesting alternative approach, but analogous in spirit (also, note that GPs would be unwieldy in my case). What safety precautions should I take when taking photos in the snow? I’m going to Queenstown, NZ in a couple of weeks and want to take my (very new, very precious) Canon 7D with me. I’ve done a little bit of research on how to protect my baby from cold climate (e.g. ) and found that the biggest problem is probably going to be condensation. Some suggestions have been to place the camera in a plastic bag or letting the camera gradually adjust to the new temperature or placing silica gel in the camera bag to absorb moisture. I am leaning toward the latter at the moment because it sounds like it’s the easiest, so I was just wondering if anyone has had any experience in this matter and could share their wisdom.  As an alternative I could take my Canon 350D, as I really wouldn’t care if that got damaged in the snow. However I’m a film student and tend to take just as many videos as photos – hence why I really want to take the 7D. But I would seriously regret it if it got damaged… dilemma!   So as I actually haven’t used a question mark in the body of text, I will specify that the question is: What safety precautions should I take when taking photos in the snow?  Cheers. The is sometimes pronounced &quot;tha&quot; (/ðə/) or &quot;thi&quot; (/ðiː/). Which is the correct pronunciation of this word? Are both correct and used interchangeably at specific places? If the second question is correct, please provide the rule of pronouncing at different places. Options for crowdsourcing GIS data? I am looking at collecting spatial information from a range of stakeholders to identify opportunities within a landscape.  However, the data that we are collecting are not presently mapped and so we wish to use an interactive method to get this information onto a map.  Which online websites/methods would people recommend for circulating to a non-technical audience to try and get them to map what they know?    Where the emphasis is on ease of use by the stakeholder. I need to find algorithm that can calculate centroid A (aka gravity center, geometric center, center of mass) from the figure where circles T1,T2,T3,T4,T5,..,Tn intersect AND length of line R from centroid to farthest corner of mentioned figure   Following information is given:   T1   Latitude    =   56.999883   Longitude   =   24.144473   Radius  =   943 T2   Latitude    =   57.005352   Longitude   =   24.151168   Radius  =   857 T3   Latitude    =   57.005352   Longitude   =   24.163356   Radius  =   714 T4   Latitude    =   56.999042   Longitude   =   24.168506   Radius  =   714 T5   Latitude    =   56.994226   Longitude   =   24.15709    Radius  =   771   Result should look like this:  A Latitude = XX.XXXXXXX    Longitude = XX.XXXXXXX  Radius = XX    As you probably already figured out, I am working on software that can find device location by closest Wifi Access Points or Mobile Base stations, as number of access points or base stations might change, I need an algorithm that can adapt to uncertain amount of points.  There are some similar questions  and , but none of them exactly answers to my question.