For example, I can run ln, nano, and programs I installed over apt like sl or worms without having to give the full path. However, when I build a program/package/software manually/using make/using something else, I have to invoke it using the full path, in my case ~/ghc/bin/ghc. How do you tell bash, or for that matter, sh, which names exist?  I know how to do this on Windows, but as far as I know, there's no equivalent of %PATH% in Linux/Unix/Ubuntu (in my case).
How to add something to PATH ? I have added like   PATH=$PATH:/home/example export PATH   and it works until I restart , after that when  I type env in PATH there is no /home/example.
I'm not sure how to solve this problem. Can you guys provide some input/hints?      Let $A=(x_1,y_1)$, $B=(x_2,y_2)$ and $C=(x_3,y_3)$ be three points in $\mathbb{R}^{2}$.      Show that the area of $\Delta ABC$ is given by   $\frac{1}{2}\left| \det(M) \right|$, where   $$M = \begin{pmatrix} 1 &amp; 1  &amp; 1\\  x_1 &amp; x_2 &amp; x_3\\  y_1 &amp; y_2 &amp; y_3 \end{pmatrix}$$ Logitech LS21 recognized as 2.0 system - Windows 8.1 doesn't detect Subwoofer I got my dad a Logitech LS21 system for Christmas. It's a 2.1 system, but it's recognized in Windows 8 as a 2.0 system (it says there is no subwoofer connected).    How would I go about getting the sub recognized?  It plays some sound now, but it's so quiet you can't hear it without putting your ear right next to it. Which experiments prove atomic theory?  Sub-atomic theories:   atoms have: nuclei; electrons; protons; and neutrons. That the number of electrons atoms have determines their relationship with other atoms.   That the atom is the smallest elemental unit of matter - that we can't continue to divide atoms into anything smaller and have them retain the characteristics of the parent element. That everything is made of atoms.     These sub-theories might spur more thoughts of individual experiments that prove individual sub-atomic theories (my guess is more was able to be proven after more experiments followed). QGIS Graphics Glitch after changing CRS What do I need for extreme macro photography? I am wanting to venture into some extreme macro photography, specifically insects, such as . After doing some research I have believe that my 1::25 macro lens will be sufficient if I am to use some extension tubes (which I have bought).  I would like to shoot the in the wild, is this possible/likely? Or is this always a catch, then release style of shooting?  Regarding the link I've posted, would this be possible with a 1:25 macro and extension tubes? I have a set of three (21mm, 31mm and 13mm). How would you go about shoot a blue bottle for example? Surely they are going to fly away? Should I use a tripod or will that cause more of a hindrance than a help? Are there any techniques/tricks I could use to get a sharp focus on my subject? Implementing a PIVOT query How can I pivot the following SELECT statement:           SELECT sc.CID,                 sc.CodeName     as OverviewText,                 scRAG.CodeName  as RAGStatusText             FROM StatusCode      sc LEFT OUTER JOIN ProjectOverview po               ON sc.CID          = po.ProjectOverviewCID              AND po.ProjectId    = 180 LEFT OUTER JOIN StatusCode      scRAG               ON po.RAGStatusCID = scRAG.CID           WHERE sc.SCID         = 18   Such statement yields the result set that follows:  CID OverviewText    RAGStatusText --- ------------    ------------- 153 Cost            Green 154 Requirements    Yellow 155 Schedule        NULL 156 Technical       NULL 157 Testing         NULL   But, I want it to return one single row with 10 values, as shown bellow:   ----------------------------------------------------------------------------------------------  | Cost | Green | Requirements | Yellow | Schedule | NULL | Technical | NULL | Testing | NULL |  ----------------------------------------------------------------------------------------------   Can I pivot on CID? Torque on a rod? I've learned that the torque on an object is just $ \text{perpendicular force}\times\text{radius}$ and that has worked well for things like seesaws but it doesn't take into account the torque of the object itself!    In the picture the rod has a total mass of 5kg, and by definition the torque on the right is greater than that on the left.  $$T=Fr$$   I am supposed to solve the question     What distance to the left of the fulcrum (triangle supporting the rod) would I have to put a 3kg weight to balance the rod?     I've tried calculating the net torque $T_{net} = I\alpha$ but I don't really know how to approach this. I'm looking for an explanation more than an answer. lsusb relevant output Bus 001 Device 006: ID 0bda:8812 Realtek Semiconductor Corp. RTL8812AU 802.11a/b/g/n/ac WLAN Adapter  Upon plugging the device it is recognized by lsusb, however when I go to wireless settings no adapter is recognized. The driver is installed (by going to software and updates -> addition drivers and selecting the open source driver). Windows 8 skype is terrible.  They've removed many buttons, most of the preferences, and have in general made it impossibly oversimplified and difficult to use.  Old Skype was fine when I had windows 7.  Is there any way to get it back on Windows 8? Related:   I know I must describe my past and current research in my personal/research statement or statement of purpose. But do I use technical terms?  I was given the advice that since the people reading my statement are mathematicians (I am applying to US for applied mathematics), they should know what I am talking about.  Although I am applying to applied mathematics, it would also be nice to hear from other fields (biology, computer science, engineering etc) about this. Where did the world go? I was playing on my main world when my laptop ran out of power.  I found a charger and woke it up, but Minecraft had crashed.  Now, it doesn't appear in the world selection screen!  I have verified that it still exists in the Minecraft folder, and the directory contents look to be in order.  Does Minecraft save an internal flag somewhere when it crashes hard?  If so, how do I reset it? Existence of irreducible polynomials over finite field Ignoring BGRT: invalid status 0 (expected 1) Using THE before some countries I have been taught that it's grammatically proper to use the before countries like "Sudan and Yemen" but I was never given a reason (if there exists any, of course) when I asked why, except for "it is one of those ambiguous parts of English language that we &ndash; as non-native speakers &ndash; should just accept without trying to look for a reason". Now, I'd like to know if there is any answer to this "why" or I should keep on believing that there are no hard and fast rules when it comes to questions like these. Why can't Mathematica integrate this? Is this arthropod non-intrusive and recommended to be left alive? Where can I find historical data on flights, specifically Delta international flights?  I need to find out about cancellations, diversions and any other flight data pertaining on particular route at a given time.  This source has to be official and stand up to legal scrutiny. I am using Log4Net with the AdoNetAppender to log messages from a simple systray application into a SQL Server 2005 database.  I want to log the machine name along with the log message because this application will be running on multiple machines and I need to know on which one the message originated.  But, I cannot find a way to expose this information via the log4net.Layout.PatternLayout that I am using with the appender.  Is there a way to log the machine name via log4net in this manner? Are repository lists secure? Is there an HTTPS version? Are repository updates secure?  As a bear of little brain from the developer side, I cannot understand why the repository list is http://security.ubuntu.com and the other http(unsecured) sites listed in /etc/apt/sources.list.  Without a certificate chain match this appears as "ask any responder for a list of packages to update" instead of "ask the ubuntu.com site..."  Can any network choose to spoof the update sites, and is this a common practice to provide a locally cached and vetted copy? The following is an excerpt from a New York Times article of April 6.     “Tonight, I ordered a targeted military strike on the air base in Syria from where the chemical attack was launched,” Mr. Trump said in remarks at his Mar-a-Lago estate in Florida. “It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons.”    Shouldn't that "from where" be either "from which" or else just "where" without "from?"