How can I use a file in a command and redirect output to the same file without truncating it?
Can I read and write to the same file in Linux without overwriting it?
How to test for minimum amount of items in inventory and execute a command if true I am using the AmazingKit plugin on my Minecraft server to make inventory kits for players. In a command block I have the following command:  /tellraw @p ["",{"text":"Iron","clickEvent":{"action":"run_command","value":"_____"}},{"text":" / "},{"text":"Gold","clickEvent":{"action":"run_command","value":"_____"}}]   Which prints the following result: Iron / Gold.  When a player clicks on Iron, what command should I write where the empty space is _____ in order to check if the player has at least (>=) 20 iron ingots in his inventory and if he/she does, remove 20 iron ingots and execute /kit Basic. If the player has less than 20 iron ingots in inventory, the command won't be executed. Instead, Insufficient amount of iron ingots will be printed out.   Same applies when a player clicks on "Gold".  I'm on 1.14 version How do I remove the LAMP stack so I can start over? I'd like to start over with my webserver and I'd like to reinstall all the LAMP packages, how do I do that? Simple chessboard exercise Given two separate annulus with centers $[C_1,C_2]$ and their corresponding radii being $[R_1,r_1]$ and $[R_2,r_2]$ respectively, larger radius being $R$. There are methods to look at whether they are overlapping or not. If they overlap how to find the overlapping area. Is there any close form expression for it?  equation of first annulus   $r_1^2&lt;(x-x_{c1})^2 + (y-y_{c1})^2 &lt;R_1^2$   equation of second annulus  $r_2^2&lt;(x-x_{c2})^2 + (y-y_{c2})^2 &lt;R_2^2$  If there are three circles overlapping, we get overlapping area as solution to set of 4 in-equations by least squares approach(Though we don't end up getting total area but, area within tangents of circles ). Upper bound and lower bound of an integral I have this problem and I don't know where to start. Can you give me some hint, please?  Suppose that $f:[a,b]\to [0,\infty]$ is a lebesgue integrable function. Let $B=\int_a^b fd\mu.$ Prove that $\sqrt{1+B^2}\leq \int_a^b\sqrt{1+f^2}d\mu\leq 1+B$. In wikipedia FKT algorithm is given for planar graphs. Not anything for complete graphs. I need to find the number of perfect matchings in complete graph of six vertices. Why does Oracle 9i treat an empty string as NULL? I know that it does consider ' ' as NULL, but that doesn't do much to tell me why this is the case.  As I understand the SQL specifications, ' ' is not the same as NULL -- one is a valid datum, and the other is indicating the absence of that same information.  Feel free to speculate, but please indicate if that's the case.  If there's anyone from Oracle who can comment on it, that'd be fantastic! Suppose $A$ is a 4x4 matrix such that $\det(A)=\frac{1}{64}$ What command should I use to rotate wood to S,N,W,E,D and U?  I read the entire world edit guide and tried some things but all the results are not satisfactory. $n$ Lines in the Plane How am I to "[u]se induction to show that $n$ straight lines in the plane divide the plane into $\frac{n^2+n+2}{2}$ regions"? It is assumed here that no two lines are parallel and that no three lines have a common point. Further, this is not a non-Euclidean problem, but I wouldn't mind a discussion on the non-Euclidean nature of the problem.  I was thinking it might be easier to show using the unit sphere.    A GOOD REFERENCE I FOUND THAT WILL BE USEFUL TO ANYONE COMING ACROSS THIS PROBLEM IS Concrete Mathematics, Graham, Knuth, Patashnik pp. 4–8. Ubuntu missing from HP boot menu I have a HP laptop with Windows 8.1 and Ubuntu 14.04 dual booted. I used to use F9 key to enter boot menu and chose Ubuntu and then GRUB would appear where I would chose Ubuntu again. This was working fine all this while. Either a hardware change or a Windows update has caused the Ubuntu option to go missing from the boot menu itself.  How do I fix this and boot into Ubuntu again? Find the limit of $\log\Big(\frac{(n^2+n)!}{n^2!n^{2n}}\Big)$ I have to prove that      $$\Big[\log\Big(1+\frac 1{n^2}\Big)+ \log\Big(1+\frac 2{n^2}\Big)+...+ \log\Big(1+\frac n{n^2}\Big)\Big] \to \frac 12$$   I know that $$\log\Big(1+\frac 1{n^2}\Big)+ \log\Big(1+\frac 2{n^2}\Big)+...+ \log\Big(1+\frac n{n^2}\Big)= \\ =\log\Big(\frac {n^2+1}{n^2}\Big)+ \log\Big(\frac {n^2+2}{n^2}\Big)+...+ \log\Big(\frac {n^2+n}{n^2}\Big)=\\ =\log\Big(n^2+1\Big)+ \log\Big(n^2+2\Big)+...+ \log\Big(n^2+n\Big)-2n\log n$$  Doing some manipulation we get:           $$\lim_{n \to +\infty}\log\Big(\frac{(n^2+n)!}{n^2!n^{2n}}\Big)=\frac 12$$      How can I prove this limit? How can there be animals on the surface in Zion's world? It is apparently canon that  in Neo's day.  However, in the first movie, The Matrix, Morpheus tells Neo that one of the things known for certain is that humans "burned the sky" in order to deny solar engery to the machines, which in turn led to the humans who survived the War being plugged into the Matrix to provide bioelectric energy to supply the machines.  If there's not enough sunlight for solar power, how can there be enough to grow plants to serve as food for animals?  Low levels I can understand -- house plants, at least, thrive in conditions too dim for solar panels to produce cost-effective power -- but every surface scene we see in the trilogy is as dark as a cloudy night; light coming only from the machines.  That wouldn't begin to support photosynthesis, which means all animal life would starve in, at most, a matter of a few years. Suddenly mysql/mariadb won't start How can I open a cmd window in a specific location? How can I open a cmd window in a specific location without having to navigate all the way to the directory I want? Can I use my laptop as a second monitor? Is it possible to make my laptop's screen act as a second monitor for my desktop computer? How exactly does time slow down near a black hole? How exactly does time slow down near a black hole? I have heard this as a possible way of time traveling, and I do understand that it is due in some way to the massive gravity around a black hole, but how exactly does that massive gravity slow down time? How is stock price determined? Is stock price determined only by the last trade that takes place?  For example, if a stock I own is trading at $3.42, and I place a Sell Limit order for $0.00, will the stock price temporarily dip to $0.00?  Likewise, if I place a Buy Limit order for $100.00 for a stock that is trading at $1.23, will the price spike to $100.00?  Is there some sort of "average price" that is reported on the stock ticker?  Thanks for your help in understanding this! Full Wi-fi/ethernet signal but no internet I'm really hoping someone here can help me, as I'm getting pretty frustrated with my macbook now. I have a late 2011 model 15" macbook pro running OSX 10.9.5 that refuses to connect to Internet on my home network. I have the same problem whether it's WiFi or through ethernet cable, I have full signal but not getting online. Every other device connects fine; android phones and tablets,xbox one, iPhone and other macbooks, all online and browsing the net. I have had no problems connecting to other networks with my macbook pro before and I just tried at a friend's house to check, with no problems. A little something, that may be a clue to someone: when I open network diagnostic tool, my macbook pro connects for something that seems like a microsecond and it tells me I'm connected to Internet and everything seems fine. My IP is 192.168.0.5 subnet mask 255.255.255.0 and IPv6 is set to automatic. None of the options are checked under the proxies tab. Now I've tried the following, in different order and a number of times, to no avail:   Renewing/turning off&amp;on/inputting manually DHCP.  Restarting/resetting the router and the macbook.  Turning WiFi on/off. Remove &amp; add services (WiFi &amp; ethernet). Checked and copied all network settings from another macbook pro that's connected and online on my network. Ran network diagnostic and assistant tools Duplicated/removed/added location Removed the /Library/Preferences/SystemConfiguration folder. Removed network password from keychain.      I've tried other things too, but can't remember what else right now.  Response from ifconfig en1:  en1: flags=8863&lt;UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST&gt; mtu 1500              ether 28:cf:da:e6:95:0a              inet6 fe80::2acf:daff:fee6:950a%en1 prefixlen 64 scopeid 0x5               inet 192.168.0.5 netmask 0xffffff00 broadcast 192.168.0.255              nd6 options=1&lt;PERFORMNUD&gt;              media: autoselect               status: active    I'm praying that someone out there has the magic words or the 2-click solution for me, but I would be grateful for a long thorough guidelines to solve it too! &lt;3        Regards Trond Internal or external oscillator I always use the internal oscillator that pics have as I have never found the need to run anything at higher frequency than 8 MHz (which is the fastest the pics I use tend to be able to go). Are there any reasons, beyond going above 8 MHz, that mean I should use an external oscillator? It just seems like one more thing to go wrong to me but I'd be interested to hear what others do.