Say I use some Linux operating system. How could I see a list of all the shells that came installed with it (either CLI shells or GUI shells)?  Typing echo $SHELL isn't good for me because it only shows me my current shell (Bash), but what I desire is to list all shells currently installed in the system.  My aim is to have a direct check of all the shells that came with my OS, especially if there are any other beside sh and Bash.
How to list available shells for use by command-line?
shred multiple hard drives Pre-1972 sci-fi short story or novel: alien(?) tunnel where people try new moves and get destroyed if they're not the correct ones What Sith Lords were turned to the Light Side? Fantasy book where a young prince becomes a mage When I was younger (11-12 years old, so the early 2000s) I once read a story where a young boy, who may have been either a young prince or a squire of some sort, is recruited by a wizard and taken to a city to train as a mage.  I seem to remember him living in dorms with the other children at this school, until he gets into difficulty with another of the boys in the dorm. He is kicked out of the dorms and ends up living above a blacksmith shop (I think).  I remember it being the first book in a series of books of which there were about 3 out at the time. I think one of the stories was about the boy going to a tower to do something or other.  Does anyone have any idea what this book series is? I haven't been able to find it for years now but it was a story I really loved. I need a little hint in a proof on convergence of a sequence. The problem I have is: Suppose $(x_n)$ is a monotone decreasing sequence of real numbers such that $\sum x_n$ converges, prove that:  $$\lim_{n \to \infty} nx_n=0$$  My idea is: proving this fact aims to prove that given $\epsilon &gt;0$ there's some natural $n_0 \in \mathbb{N}$ such that if $n &gt;n_0$ we have $|nx_n|&lt;\epsilon$.  Now, I know that $\sum x_n$ converges, so that given $\epsilon'&gt;0$ there's some $k_0 \in \mathbb{N}$ such that if $k &gt; k_0$ we have:  $$\left|\sum_{i=1}^{k}x_i - S\right|&lt;\epsilon'$$  Where $S = \sum x_n$. Now, since $(x_n)$ is monotone decreasing we know that we must have $x_1 &gt; \cdots &gt; x_k$ so that the sum of all $x_i$ should be less or equal to $k x_k$. So I know that I have:  $$\left|\sum_{i=1}^{k}x_i - S\right|\leq\left|\sum_{i=1}^{k}x_i\right|+|S|\leq|kx_k|+|S|$$  I feel that the proof will come from this, however I'm stuck at this point. Can someone give just a little hint on how to proceed from here?  Thanks very much in advance for your help. Finding an item in a List using C# how long does the care take to reach the last pole algebra word problem There are 20 poles with a constant distance between each pole. A car takes 22 seconds to reach the 12th pole starting from the first pole, with a constant speed between each pole. how many seconds will it take to reach the last pole?   Is the answer 36 seconds?   since $\frac{22} {12}  = 1.83 $  $1.83 \times 20 = 36.67 $ Does transparency work in eevee I have been trying to create a transparent lens using the eevee rendering engine in 2.8 but the transparency slider has no effect. Has this feature not been implemented yet? I've looked all over the Web for an answer with no luck. I'm a noobee so am probably doing something wrong. Consider the following example:  \documentclass{article} \newtheorem{Theorem}{Theorem} \begin{document} \begin{Theorem} On the other hand, this one has only one claim. \end{Theorem} \begin{Theorem} \begin{enumerate} \item First claim \item Second claim \end{enumerate} \end{Theorem} \end{document}   Typesetting it results in:    Notice there is extra horizontal space before the first item in the list of the second theorem.     Is there a sensible way to get rid of that?   Ideally, the solution would work with amsthm, thmtools, enumitem.  N.B.: this is related to  but not quite the same. Excessive water when cooking scallops This is partly a continuation of  question, since that one was already closed, but my question is about a specific problem encountered the last time I cooked scallops.  I got the pan up to a reasonable temperature and put the scallops in, and as they were cooking, TONS of water came out of the scallops and filled the pan.  I poured it out, continued cooking, and more water came out.  Several iterations later, I thought they were done, but they were still very raw inside, so we ended up tossing the batch (it definitely wasn't sushi grade).  Where did all the liquid come from, and is there any way to avoid that the next time? How to write (La)TeX (with parentheses) [or any other TeX-related logo] I'm looking after a macro to write the (La)TeX logo (with parentheses), i.e. something similar to \TeX, \LaTeX, but where the output includes ()'s. Weird behavior when overriding gnome alert styling? After playing around with the i3 tiling window manager, I had my fill and decided to uninstall it and continue using gnome. However, to my dismay, something in i3 overrode the default gnome alert box. For example, when connecting to wifi, I get a gray or blue box instead of the nice ubuntu popups. The screenshot says it all. Any ideas?    (See top right corner) Uniform continuity of $\sin(x\sin x )$ for all $x\in (0,\infty)$ What Android emulators are available? I will like to know some of the android emulators that work really well with Ubuntu 11.10 and above. I want to try 'whatsapp' on Ubuntu through an android emulator. Thanks in advance Detection of the Electric Charge of a Black Hole I'm having difficulty solving an exercise in my course.  The question is:      Prove that $n!\geq 2^n$.   We have to do this by induction. I started like this:   The lowest natural number where the assumption is correct is $4$ as: $4! \geq 2^4 \iff 24 \ge 16$. The assumption is: $n! \ge 2^n$.   Now proof for $(n+1)$ which brings me to: $(n+1)! \ge 2^{(n+1)}$  I think I can rewrite it somehow like this:  $$ {(n+1)} \times {n!}  \stackrel{\text{(definition of factorial)}}{\ge} 2^n \times 2 $$  $$ (n+1) \times 2^n \ge 2^n \times 2 $$  Then I think I can eliminate the $2^n$ and have something like this: $n+1 \ge 2$, or $n \ge 1$.  But I think I'm wrong here some where and was hoping somebody has some advice on this. How can I prove the above assumption?  Any help would be appreciated, kind regards. Determine all functions satisfying $f(x + f(x + y)) + f(xy) = x + f(x + y) +yf(x)$ I'm using the Webform module for Drupal 8. The module confirmation settings for a form are the following:   Page (redirects to new page and displays the confirmation message) Inline (reloads the current page and replaces the webform with the confirmation message.) Message (reloads the current page/form and displays the confirmation message at the top of the page.) URL (redirects to a custom path or URL) URL with message (redirects to a custom path or URL and displays the confirmation message at the top of the page.)   But how am I able to submit a form via AJAX so that the page doesn't reload on submit, but a confirmation message still replaces the form? What did I do wrong?    EDIT:  Here is the solution which works:  First you have to hook the form alter function and set an AJAX callback (as in ):  use \Drupal\Core\Form\FormStateInterface;  function MYTHEME_form_alter(&amp;$form, FormStateInterface $form_state, $form_id) {   if ( isset($form['#webform_id']) &amp;&amp; $form['#webform_id'] == 'MYWEBFORM' )   {     // add an AJAX callback to the form submission     $form['actions']['submit']['#ajax'] = array(       'callback' =&gt; '\Drupal\MYMODULE\Controller\DefaultController::processFormSubmission',       'event' =&gt; 'click',     );   } }   Then in the processFormSubmission function you can process the form (put use \Drupal\Core\Form\FormStateInterface; at the top of your file) like:  // Instantiate an AjaxResponse Object to return. $ajax_response = new \Drupal\Core\Ajax\AjaxResponse();  /* do sth */  // in the DOM: replace the form with the text 'form submitted' $ajax_response-&gt;addCommand(new \Drupal\Core\Ajax\HtmlCommand('#MYFORM', 'form submitted'));  return $ajax_response; How can I add the session name to my screen status display? This is my current .screenrc files which is mostly copied from the link in the code  #First iteration 2014-09-06, not quite sure of stuff to add # got a fancy hardstatus line noted below hardstatus on hardstatus alwayslastline # hardstatus string "%w"  # blagged this hardstatus like from https://bbs.archlinux.org/viewtopic.php?id=55618, not quite sure what it does hardstatus string '%{= kG}%{C}Screen: %{c}%{= kG}[%= %{= kw}%?%-Lw%?%{r}(%{W}%n*%f%t%?(%u)%?%{r})%{w}%?%+Lw%?%?%= %{g}][%{C} %d-%m %{W}%c %{g}]'   I now want the session name to appear in it as well, and the one I have settled on is from this answer -   The solution runs along these line:  hardstatus string '%H:%`' backtick 0 30 30 sh -c 'screen -ls | grep --color=no -o "$PPID[^[:space:]]*"'   It is an area I am not familiar with and I wonder how the backtick command fits in it, ie whether it is a screen command at all. Doubt on Rechargable LED Emergency bulb I have recently seen a  and I  was wondering how it is working.  In the event of a power failure, the LED bulb will turn ON automatically. That is, when the switch is ON and mains power goes off the bulb will detect that and turn ON. If the switch is OFF bulb will not turn ON. When mains are ON and the switch is ON the bulb will start recharging again.  It is just like a normal bulb. See the   My question is, how the bulb will detect the event of mains failure? Can somebody give me a hint on this?