I am trying to capture the currently logged in user on the linux box into a variable and then use the variable to insert it into a text file and replace the username in that file  in the file (live.conf) i want to replace the line : "live_user=whatever"  with "live_user=myvariable"  My script looks like this :  #!/usr/bin/env bash  username=${USER:=$(/usr/bin/id -run)}  sed -i -r 's/^#?(live_user)\s*=.*/\1=$username/' live.conf  exit 0   however the result is it replaces the line now to look like this :  "live_user=$username" and not the actual variable...  Anyone have any ideas on how i can make this script work ?
I tried the following code to replace QQ with ZZ, but it doesn't do what I want:  var1=QQ sed -i 's/$var1/ZZ/g' $file   However, this code does what I want:  sed -i 's/QQ/ZZ/g' $file   How do I use variables in sed?
"Reality" of EM waves vs. wavefunction of individual photons - why not treat the wave function as equally "Real"? In thinking how to ask this question (somewhat) succinctly, I keep coming back to a Microwave Oven.  A Microwave Oven has a grid of holes over the window specifically designed to be smaller in diameter than the wavelength of the microwaves it produces, yet larger than the wavelengths of the visible light spectrum - this is so you can watch your food being heated without getting an eye full of microwaves.  The "realness" of electromagnetic waves seems indisputable - both from the microwave example above, and also because if I want to broadcast a radio wave with a certain wavelength, then I need to make sure I have an antenna of corresponding length to produce the wave I'm looking for.  Furthermore, we discuss and treat these waves as real, measurable "objects" that exist and can be manipulated.     Now, if I want to describe the behavior of my Microwave Oven in the framework of QM (let's pretend my oven is going to only produce 1 photon of energy corresponding to a wavelength of the microwave spectrum for simplicity) then I'll describe the behavior of that photon as a wavefunction that evolves over time and gives a probability distribution within my microwave that similarly does not allow the photon to pass through the safety grid and exit the oven cavity giving me a retinal burn.  The difference is, the wavefunction is never treated as something "real" in this description.  When the safety grid is described as working to protect you because it has holes smaller than the wavelength of the classical waves it's blocking, this is a useful description that seems to describe "real" objects/be-ables.  While it is possible to describe why an individual photon has low probability of passing through the same grid but extended physical properties such as wavelength (in space) are treated as non-real because we're dealing with a point particle and with behavior described by something we also treat as non-real (the wavefunction); it seems unclear to me why we insist this wave function which predicts behavior of physical measurements so well is somehow "non-real."    Put another way, if we have no problem treating EM waves as "Real," then why do we insist on treating the wavefunction that describes the same behavior as "unreal?"  I understand there is recent research (Eric Cavalcanti and his group for one) trying to argue this point, but as every respectable physics professor, I've ever encountered, has treated the wavefunction as an indisputably non-real mathematical tool, I needed to ask this community for an answer. Smart Phone's camera socket I just want ask how the socket in the image is called?   I couldn't really find and the closer I could get is only Raspberry's module. I am having trouble with the following sentence:      "The complexity and diversity of the new platforms is worrying us."   If "complexity" and "diversity" constitute two subjects, then the verb should presumably be "are"; however, the sentence feels more natural with "is". Is this correct? Is there a linguistic term for this occurrence?    The following questions address the general topic of compound subjects, but not specific cases like this:             And the following question seems to have somewhat inconclusive answers:         So this question is not really a duplicate of these three. Suppose that we have a vector space $V$ and the subspaces $U=\{(x,x,y,y)\in F^4:x,y\in F\}$ and $W=\{(x,x,x,y)\in F^4:x,y\in F\}$. Then how comes $$U+W=\{(x,x,y,z)\in F^4:x,y,z\in F\}?$$ How to hear my voice in speakers with a mic? Ubuntu 16.04.1 has appeared as .rar file. How do I burn it to a disk to use to install Ubuntu? I am interested in using Ubuntu for the fist time, so I went to the Ubuntu download page (), to get the download file. When the file downloaded he file, it appeared in WinRAR, so I cannot burn the file to a DVD. Can anybody point me in the right direction as to how to burn this file to a DVD when the file appears as a WinRAR file? Any help would be great appreciated. Thanks :) Using nohup to keep a script running indefinitely I am very new to Linux and I've only been using it to SSH to my web server using Putty. The issue I am having is this:  Basically I've got 2 php scripts. One get_tweets.php constantly listens for tweets on twitters Streaming API whilst the other - parse_tweets.php logs these into a db. In order for these to work they've to be kept running continuously.   I've been using the following commands to run them in the background and from what I've seen they run for most of the day, however whenever I log on to my computer in the morning the scripts have stopped and I've to run commands again.  nohup php my_script.php &gt; /dev/null &amp;   I'm just wondering if that is normal based on the commands I am using, should they run indefinitely when using nohup and if not what is the alternative? A CRON job?  Thanks for the help EntityFieldQuery order by title iPhone App › Add voice recognition? RF Energy Harvesting Why can energy invested in RF radiation not be harvested fully? What are the main factors that affect this? Is there any significant research nowadays that fully describes this process? I stand on the conclusion: "Energy moves from one form to another.", but in this case why can it not be harvested in that quantity to use it for powering low-power devices or store it in significant quantities in some batteries for later use? Why is it not profitable nowadays and why is it not used today like energy from water, wind and other energy sources? Insert into ... values ( SELECT ... FROM ... ) I am trying to INSERT INTO a table using the input from another table. Although this is entirely feasible for many database engines, I always seem to struggle to remember the correct syntax for the SQL engine of the day (, , , , and ).  Is there a silver-bullet syntax coming from an SQL standard (for example, ) that would allow me to insert the values without worrying about the underlying database? The world I've been playing crashed recently and took the level.dat with it, so I've recreated it, however I have no idea what my seed used to be, and I really don't want to end up with another corrupted game world from exploring with the wrong seed.  How can I recover the seed which was used to generate my world? Using same modulus for RSA I know that there exist some attack when using same modulus.      But with a little modification, $m$ is the plain-text $N$ is the RSA modulus $r_1, r_2$ is the random padding $e, s$ is the public exponent $C_e, C_s$ is the cipher-text  encrypt as follow $$С_e = (m + r_1)^e   \bmod N$$ $$С_s = (m + r_2)^s   \bmod N$$  If attacker only knows $C_e, C_s, r_1, r_2, e, s, N$. Is it possible to know $m$?  It seems the  does not work? Image data URI and SEO Do you think the use of image data URI is SEO friendly?   On the one hand saves you a HTTP request. On the other hand it really messes up your code. Especially for image files larger than 20KB or moving GIF image files of up to 200KB, the quantity of code inserted is enormous. As Googlebot reads usually from top to bottom, all data after the image data URI encoding will be harder to rank well in Google.   Consider that image data URI is not in the CSS files as they should normally be and for the time being I can use only TinyMCE editor which provides me with just two options, either insert image with the image data URI method or the traditional image link.   I would like to know which is more search engine friendly. A generic question across most board games: once a player has taken their turn (taken their finger off the piece they are playing), should they be allowed to change their mind?  Similarly, if a player forgets to take a privilege, such as an occupied building in Puerto Rico giving an extra worker, or plantation, if they remember a few moves later, should they be allowed to take the privilege?  Very few rules explicitly express how these events should be dealt with, so they are generally left up to the group. However, my group's rules will change depending on the personality of the players playing (not all members are available each time we play). I would like to make this consistent, and would appreciate feedback on how others deal with this scenario. vectorized array creation from a list of start/end indices How do you remove duplicates from a list whilst preserving order? $\left|x_{n+1} - x_n\right| < C\left|x_n - x_{n-1}\right|$ prove this is Cauchy Latexmk and the location of Asymptote's generated files I am trying out Asymptote with latexmk and I would like to automate the interaction.  Consider the following latex document test.tex:  \documentclass{minimal} \usepackage{asymptote} \def\asydir{asymptote}  \begin{document}  Testing Asymptote:  \begin{asy} settings.outformat = "pdf"; unitsize(2cm); draw((0,0) -- (1,0)); \end{asy}  \end{document}   In my latexmkrc I have the  for Asymptote integration:  sub asy {return system("asy -o asymptote/ \"$_[0]\"");} add_cus_dep("asy","eps",0,"asy"); add_cus_dep("asy","pdf",0,"asy"); add_cus_dep("asy","tex",0,"asy");   Running latexmk -pdf test.tex generates test.pdf in the current folder and test-1.asy and test-1.pdf in the asymptote folder -- but only if   I manually created the asymptote folder prior to running latexmk. The folder specification in the latex document (\def\asydir{asymptote}) and latexmkrc (-o asymptote/) are identical.   I would like latexmk to read asydir from the main tex file, create the directory if it does not exist and run asy with the read output folder.  Is this possible? Find all natural numbers $n$ and $m$ for which $n^m=(n-1)!+1$