Why the following redirection doesn’t work?
Why can't certain programs (like readlink) take input from a pipe?
Consider the group $\mathbb{Q}$ under addition of rational numbers. If $H$ is a subgroup of $\mathbb{Q}$ with finite index, then $H = \mathbb{Q}$.  I just saw this on our exam earlier and was stumped on how to show this. Any ideas? WPF textblock binding with List does anyone know if there is a simple way to bind a textblock to a List. What I've done so far is create a listview and bind it to the List and then I have a template within the listview that uses a single textblock.  what I'd really like to do is just bind the List to a textblock and have it display all the lines.  In Winforms there was a "Lines" property that I could just throw the List into, but I'm not seeing it on the WPF textblock, or TextBox.  Any ideas?  did I miss something simple?  Here's the code  &lt;UserControl x:Class="QSTClient.Infrastructure.Library.Views.WorkItemLogView" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"          Width="500" Height="400"&gt; &lt;StackPanel&gt;     &lt;ListView ItemsSource="{Binding Path=Logs}" &gt;         &lt;ListView.View&gt;             &lt;GridView&gt;                 &lt;GridViewColumn Header="Log Message"&gt;                     &lt;GridViewColumn.CellTemplate&gt;                         &lt;DataTemplate&gt;                             &lt;TextBlock Text="{Binding}"/&gt;                         &lt;/DataTemplate&gt;                     &lt;/GridViewColumn.CellTemplate&gt;                 &lt;/GridViewColumn&gt;             &lt;/GridView&gt;         &lt;/ListView.View&gt;     &lt;/ListView&gt; &lt;/StackPanel&gt;     and the WorkItem Class  public class WorkItem {     public string Name { get; set; }     public string Description { get; set; }     public string CurrentLog { get; private set; }     public string CurrentStatus { get; private set; }     public WorkItemStatus Status { get; set; }     public ThreadSafeObservableCollection&lt;string&gt; Logs{get;private set;}   I'm using Prism to create the control and put it into a WindowRegion          WorkItemLogView newView = container.Resolve&lt;WorkItemLogView&gt;();         newView.DataContext = workItem;         regionManager.Regions["ShellWindowRegion"].Add(newView);   thanks How is dark energy consistent with conservation of mass and energy? I initially thought that dark energy must in some way violate conservation of mass and energy since the component of the energy density of space that comes from dark energy is constant, and space is expanding. Therefore, as space expands the energy in the universe that comes from dark energy would increase. I presumed the source of this energy was not coming from the conversion of other types of energy to dark energy, so it must violate conservation.  I decided to Google this and came upon this article:    It says that dark energy does NOT violate conservation and quotes Carroll, Press, and Turner (1992):  "…the patch does negative work on its surroundings, because it has negative pressure. Assuming the patch expands adiabatically [i.e. without loss or gain of heat], one may equate this negative work to the increase of mass/energy of the patch. One thereby recovers the correct equation of state for dark energy: P = – ρ c2. So the mathematics is consistent."  Is there a way to explain this in layman's terms? (The blog attempted to do this, but it was very unclear to me.) More specifically, can you explain where my initial train of thought described above fails when I erroneously concluded that dark energy violates conservation?  Thank you. How to easily build your own Linux Distro? I wanted to have a go at creating my very own Linux Distribution. Could you suggest some nice and easy-to-follow tutorials (preferably text based and not videos). I have heard something about Arch Linux but I don't know how to go from there. What do I need? Correct usage of suspended hyphens I have seen some people using them while others not. Should I still use a suspended hyphen in the following snippet?     I have used upper- and lowercase in my script. The replier's From email address is modified when Marketing Cloud RMM forwards an email to the routing address We've set up RMM to forward replies to routing address and SFMC adds our subdomain to the replier's From email address (i.e. replier@gmail.com becomes replier.gmail.com@oursubdomain.com). However, their reply-to address remains the same.  It seems like DMARC Forward Reply Rewrite is enabled, but we were advised not to touch it as that may affect email deliverability.  Is there any workaround to this? And what will happen if we disable this feature? How to remove duplicate values from a multi-dimensional array in PHP How can I remove duplicate values from a multi-dimensional array in PHP?  Example array:  Array (     [0] =&gt; Array     (         [0] =&gt; abc         [1] =&gt; def     )      [1] =&gt; Array     (         [0] =&gt; ghi         [1] =&gt; jkl     )      [2] =&gt; Array     (         [0] =&gt; mno         [1] =&gt; pql     )      [3] =&gt; Array     (         [0] =&gt; abc         [1] =&gt; def     )      [4] =&gt; Array     (         [0] =&gt; ghi         [1] =&gt; jkl     )      [5] =&gt; Array     (         [0] =&gt; mno         [1] =&gt; pql     )  ) Leagues still count association bonus Let $G$ be a finite group, say a group with $n$ elements, and let $\emptyset \neq S \subseteq G$. Suppose $e \in S$, and that $S$ is closed with respect to multiplication. Prove that $S$ is a subgroup of $G$.    Let $G = \{a_1, \ldots, a_n\}.$ Let $a_i \in G.$ Then any number of $a_ia_1, a_ia_2, \ldots, a_ia_n \in S,$ since $S$ is closed under multiplication. One of those $a_ia_j$ is $e$ since $e \in S.$ Then either $a_i$ or $a_j$ is $a^{-1}.$ Would this argument work? How to deal with variable income in the budget We have a budget planned out for various categories, and in order to make ends meet we count on child support for my wife's child from a previous marriage.  However, lately we have not been receiving this amount.  How do we deal with this in the budget?    My wife has just been "borrowing" it from our savings, but I don't think that is reasonable given that I find it highly unlikely we will ever be able to recover it.  On the other hand, she doesn't think it reasonable to cut out of her budget and cutting it out of the budget for the kids (which is where it really should be going!) isn't reasonable either. I was trying to prove this inequality using induction, but couldn't do.  Question: Suppose $a$ and $b$ are real numbers with $0 &lt; b &lt; a$. Prove that if $n$ is a positive integer, then:  $$a^n-b^n \leq na^{n-1}(a-b)$$ Divergence of $\frac{ \hat {\bf r}}{r^2} \equiv \frac{{\bf r}}{r^3}$, what is the 'paradox'? I am trying to pull logs and doing few others things directly. written a small line BASH but not working. I am sure thats with IF Condition.    sed -rne '/21:25:07/,/21:50:07/ p'  server.log.2015-04-21 &gt; /tmp/filename.log ; du -sh  /tmp/filename.log ;  if [`du -sh  /tmp/filename.log` -gt 0] then gzip /tmp/filename.log ; How to use aes-encryption in PostgreSQL? ArrayList contains case sensitivity Is it possible to make abstract classes in Python? Lowering elevation of lake using QGIS I am in QGIS. I have a raster layer of mountains and a lake. I have a vector layer (shapefile) of the lake. It sits nicely where it supposed to be over the raster level. I am going to convert this height map to an STL so that I can cnc this out of wood, so I'd like the actual lake to be something like 200 feet lower than it shows on the raster layer so that I can fill it with blue epoxy. I have read a lot of clipping and everything else, and I am lost. Are quotes needed for local variable assignment? Can I safely omit quotes on the right side of a local assignment?  function foo {     local myvar=${bar}     stuff() }   I'm mainly interested in bash, but any info on corner cases in other shells are welcome. How to disable "time travel" entirely? Is there evidence of dark matter in our galaxy? Is there evidence of dark matter in our galaxy?  How can we measure this, say, how many percent of the center of our galaxy is dark matter?  I did not find the answer in the question