when we run a normal command we just type the name of it but why we use ./ instead of just typing its name when running the script?
While executing a C program, a.out, using the Ubuntu terminal, why do I always need to type ./ before a.out, instead of just writing a.out? Is there solution for this?
I'm trying to parse json response.. but keep getting this error      Invalid conversion from runtime type List ANY> to Map String,ANY>   Map&lt;String, Object&gt; MapLv3 = new Map&lt;String, Object&gt;();      Integer x2 = 0; for (Object oh : CallsList){     MapLv3.put(String.valueof(x2), oh);     x2++; } index = x2; System.debug('Map Lv 3 ==&gt;'+MapLv3);  Map&lt;String, Map &lt;String, Object&gt;&gt; Map3 = new Map&lt;String, Map &lt;String, Object&gt;&gt;(); for (Integer a2 = 0; a2 &lt; index; a2++){     Map3.put(String.valueof(a2),(Map&lt;String,Object&gt;) MapLv3.get(String.valueof(a2))); } System.debug('Segment ==&gt;'+Map3.get('0').get('segments')); Where can I get a clean ISO of a specific build of Windows 10? I need to repair my Windows 10 installation. Where can I get a clean ISO (with install.wim, no Install.ESD, so that I can run DISM against the WIM) of the specific Windows 10 build required for this?  In my case, I need the Anniversary update (Build 14393), Creators Update (Build 15063) or Fall Creators Update (Build 16299.15). Normal subgroup of prime order is characteristic I'm stuck on this exercise from Herstein's topics in algebra:  Suppose that $G$ is a group and $|G| = pm$, where $p \nmid ~ m$ and $p$ is a prime. If $H$ is a normal subgroup of order $p$ in $G$, prove that $H$ is characteristic.  How to prove that? What we know:   $H$ and $\varphi(H)$ have prime order $p$, so they must be cyclic and abelian They are both normal subgroups of $G$   how to show that, in fact, we have $H = \varphi(H)$ for every automorphism $\varphi$ ? Give a deduction of $\forall y \exists x (x=y)$  My thinking is I can prove $\exists x(x=y)$ then use generalization theorem， which is equivalent to prove $\neg \forall x \neg (x=y)$ but I got stuck proving this... thanks in advance  Sorry that I did not specify what deduction system that I want to use here, it is the deduction sequence  where ai is either Axiom or original hypothesis or obtained from MP How to use notify-send with crontab? I really read many tutorials, but crontab doesn't start notify send.  What I've tried:   etc/crontab  added at the end:  15 * * * * notify-send 'crontab' 'test'  with crontab interface:  crontab -e   added at the end:  15 * * * * notify-send 'crontab' 'test' How to get a list of appendices? How to get a list of appendices like the list of figures and list of tables? How to set it on a separate page, like the list of figures and list of tables? How do I enable or disable the global application menu? I'm fairly excited for Unity, as it looks like a promising new direction for Ubuntu.  However, I do have a concern - will it be possible to use Unity without the global menu?  I have my window manager set to focus-follows-mouse/sloppy focus, and find the productivity gains to be immense. Sloppy focus is incompatible, however, with global menus, as it is possible for the focus to change while you move from window to menu.  Will Unity support an option to use window menus while still using Unity? What are good books/other readings for elementary set theory? I am looking to expand my knowledge on set theory (which is pretty poor right now -- basic understanding of sets, power sets, and different (infinite) cardinalities). Are there any books that come to your mind that would be useful for an undergrad math student who hasn't taken a set theory course yet?   Thanks a lot for your suggestions! What is the difference between confidence intervals and hypothesis testing? I have read about   with some commentators suggesting that hypothesis testing should not be used. Some commentators suggest that confidence intervals should be used instead.    What is the difference between confidence intervals and hypothesis testing? Explanation with reference and examples would be appreciated. What is AC actually? What is actually alternating current (AC)? And direct current (DC)? I've been reading several books about basic electric circuits analysis and they are contradictory.   Some books say that AC is the same as the sinusoidal stationary state. That is, a sine or cosine function (actually, they are the same only shifted horizontally). For instance, \$v(t) = A \sin(\omega t + \phi)\$. Acording to these books, DC is totally stationary (static), that is, the voltage and current are not time-dependant (\$v(t) = k\$, where \$k = \mathrm{const.}\$). Currents have the same form as voltages on each of these cases. According to other books, AC is any current that is changing (that is alternating) his sign over time (\$t\$). With maths notation: \$i(t_1) &lt; 0\$ and \$i(t_2) &gt; 0\$ for some \$t_1\$ and \$t_2\$ where \$t_1 \neq t_2\$. It could have any shape as long as it's alternating his sign.   I'm inclined to think that in practice wins the first option but maybe it's better the etymology of the second option.  Some other cuestions have relation to this:   Is AC a voltage that is the sum of a sinusoidal stationary state and a constant voltage? For instance, \$v(t) = A \sin(\omega t + \phi) + k\$. Is AC a shawtooth wave? I've got a custom loop that I'm using to display some Real Estate listings that will be available within 60 days. I'm calling it with the following function:   &lt;?php  $sixtydays = date('Y/m/d', strtotime('+60 days')); $paged = (get_query_var('paged')) ? get_query_var('paged') : 1; $query = new PostsOrderedByMetaQuery(array(   'post_type' =&gt; array('post', 'real-estate'),   'meta_key' =&gt; 'Time Available',   'meta_compare' =&gt; '&lt;=',   'meta_value' =&gt; $sixtydays,   'paged' =&gt; $paged,   'orderby_meta_key' =&gt; 'Price',   'orderby_order'    =&gt; 'ASC' )); ?&gt; &lt;?php while ($query-&gt;have_posts()) : $query-&gt;the_post(); ?&gt;   While the loop works great, I can't get it to paginate. It shows the first 10 (my default) posts but doesn't show the pagination. The only way to display all posts is to show them on one page by adding 'posts_per_page' =&gt; -1, I have similar loops on other pages that have no problem paginating. The only difference with this one is that there are two meta keys that are filtering the posts.   I'm using WP Page Navi for this and the rest of my pages. I'm closing the loop and adding the pagination using the following code:   &lt;?php endwhile; // End the loop. Whew. ?&gt; &lt;?php wp_pagenavi(); ?&gt; &lt;?php wp_reset_query(); ?&gt;   How can I go about fixing this? The strange thing about the maximum in Planck's law I read that it makes a difference whether you calculate $\frac{dE(\lambda) }{d \lambda}=0$ or $\frac{dE(\omega)}{d \omega}=0$ in the sense that the maximum energy density with respect to the wavelength does not coincide with the frequency maximum that one would assume to be at $\omega_{max} = \frac{c}{\lambda_{max}}$. Actually, I do not understand why this is so ( Now, I am only interested in a pure physical explanation, mathematically this is clear and due to the chain rule). Does anybody know how to explain this odd thing?  Somehow I feel that the core of the question has not been completely answered. Although I can easily look up wikipedia, where the need for the chain rule is explained, I am rather interested in understanding where the following argument breaks down, which seems to be why this question has caused some confusion in the past(as you can see by googling this question):  So we have $E(\omega)$ the energy radiated at a given frequency. Now this function has a maximum somewhere, so there is a frequency where a maximal amount of energy is emitted. In other words: If you add the sum of the photon's energies at each frequency that are emitted, you will notice that the maximum is reached at this frquency. Now $E(\lambda)$ tells you basically the same for the wavelength, but again: We know where at which frequency the maximal amount of energy is radiated, so we know the corresponding wavelength.   I think there is a need to explain this.   If anything is unclear, please let me know. Is it possible to set the "urgent" flag in Gmail for outgoing mail? I'd like to be able to flag time-sensitive emails as such. I'm using the beamer miniframes theme (with subsection=false) and the compress option. Currently the navigation shows the dots for each subsection side-by-side. I would prefer if there would be a horizontal space (e.g. with the width of a dot) between the dots of each subsection. Is this possible? Right now it looks like:  Section 1 oooooo  And I would prefer it to look like:  Section 1 ooo ooo  MWE: \documentclass[compress]{beamer}   \useoutertheme[subsection=false]{miniframes}   \begin{document}   \section{Sec 1}   \subsection{}   \begin{frame}[t]     hi   \end{frame} \subsection{}   \begin{frame}[t]     hi   \end{frame} \end{document}` Why doesn't archive.ubuntu.com use HTTPS? I always see instructions for adding the Universe and Multiverse repositories that look something like the following:  sudo add-apt-repository -y "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc) main universe restricted multiverse"   Recently I tried editing this to use HTTPS instead and was dismayed to find that archive.ubuntu.com doesn't appear to respond to HTTPS. Now I wonder how feasible it would be, or what damage could be done, if an attacker were to successfully perform a man-in-the-middle attack here?  Am I being too paranoid, considering the role these repositories perform on a system? Export Windows 7 search results to a text file What is the source for defaulting to plain English readings of non-game terms? How do I Sort a Multidimensional Array in PHP I have CSV data loaded into a multidimensional array. In this way each "row" is a record and each "column" contains the same type of data.  I am using the function below to load my CSV file.  function f_parse_csv($file, $longest, $delimiter) {   $mdarray = array();   $file    = fopen($file, "r");   while ($line = fgetcsv($file, $longest, $delimiter))   {     array_push($mdarray, $line);   }   fclose($file);   return $mdarray; }   I need to be able to specify a column to sort so that it rearranges the rows.  One of the columns contains date information in the format of Y-m-d H:i:s and I would like to be able to sort with the most recent date being the first row. Explain proof by contradiction. Factorial of 0 - a convenience?