I have two directories with subdirectories and files inside. How can I find the difference of lines in these directories using the command-line?
I have two directories that should contain the same files and have the same directory structure.  I think that something is missing in one of these directories.  Using the bash shell, is there a way to compare my directories and see if one of them is missing files that are present in the other?
Comments/tips on a (non Latex) pdf including mathematical formulas My goal : I correct copies from students that I scan to pdf. I wish I could make the annotations on the scanned copies rather than on the physical paper. Today, I have to scan the copies again to have my annotations transferable to students by email. Since most of the annotations are similar, I wish to have a stock of annotations I could transfer on the copies.  I went through a lot of technologies, including many "StackExchange Questions" here. I considered pdfcomment, cooltips, fancytooltips, the OCG family (ocgx, ocgp, ocg2, ...), etc.  Two tracks attracted more specifically my attention :    pdfcomments : I like the mouseover to see the comment, the capabillity to move the annotation around so I can have a stock on a pdf and I can copy it onto the scanned copies. This would be my choice if there was not a main drawback : it accepts only plain text when I need to use mathematical notations. (It needs selected pdf readers). Because you can move comments, you can put them on any pdf, even if it is not compiled from Latex or if you don't have the source. fancytooltips : I like the mouseover to see the comment, and the capability to use LaTeX mathematical formulas and images. Drawbacks : I can't move the annotation from a pdf document to the copies. (It works with very few pdf readers.) . I am not sure whether I can put tips on non Latex pdfs.   Is there a way to have pdfcomment have images/Latex mathematical formulas (or references to formulas that can show with a mouseover) ? Or is there a way to transfer fancytooltips to a non Latex pdf ? Or are there other techniques to achieve the goal ? Catching poisoned arrows When catching an arrow tipped with poison (like the ones used by yuan-ti) with an ability like the one the monk has or the one given by arrow catching gloves: does the ability reduce the poison damage? If so, is the total damage or the piercing one caused by the arrow only the damage that must be downed to 0 to catch the missile? Is there a way to determine the respective canonical status of Tolkien's Middle-earth related works? It is almost always difficult to determine the canonicity (if that's a word) of different works within a fictional universe, but the problems are even more complicated in regards to Tolkien's Middle-earth/Arda related material.  It is safe to say that LotR, the second edition of The Hobbit, and probably the published Silmarillion are canon.  But even the published Silmarillion is, in large part, the work of Christopher Tolkien, although to a lesser degree than it is the work of his more famous father.    When we look at the rest of the corpus, things become even more opaque.  Unfinished Tales contains different versions of the same stories.  The same is true, in even greater degree, of The History of Middle-earth.  These volumes might be considered an almost equal endeavor on the parts of Christopher and J.R.R Tolkien.    Is there a tentative canon of Tolkien's Middle-earth related works, and if not, is it possible to create one?    With such a large body of work, of varying degrees of canonicity, it would be very helpful to have something like the now-outdated levels of canon associated with the Star Wars universe, ranked by a series of letters.  Has anyone put together such a system for Tolkien's Middle-earth related works? What solutions does the equation 4x≡2mod10 have? (Hint, it will have more that one.) What about solutions to an equation ax≡dmodn, where d=gcd(a,n)? What solutions does the equation $4x\equiv2\mod10$ have? (Hint, it will have more that one.) What about solutions to an equation $ax\equiv d\mod n$, where $d=\gcd(a,n)$?  This is the question that appeared in our universities last year paper. But it seems very difficult for me like for first part I am able to solve by simplifications I got $x=5\cdot Z +3$ as solution which makes sense and seems fair but for the second one, I have no idea how can I approach that. Can you please help me out with that one. I tried to simplify that by using Euclidean algorithm but still, I didn't get any idea that what actually the solution will be. My final exam is on 2nd of next month and because of covid I am unable to contact in person for any help. So any help from this site will be appreciated. Thank you for looking at this question! Use of Indefinite Articles(a,an) Consider the following sentences:  I am staying in a hotel nearby. I am staying in an hotel nearby.  I know that both are correct. But I would like to know why? I do not see any proper reason for the second one as the 'h' is not silent as in French. So, what could be the reason? How do I list all available shell builtin commands? We know bash supports number of  buitin commands  like:  $ type type cd help command type is a shell builtin cd is a shell builtin help is a shell builtin command is a shell builtin   I want to get list of all available shell builtin commands. How do I do that by command-line? Has user testing found that the "three horizontal bars" for main menu on mobile is commonly understood? Since canonical is  Ubuntu One, what are the possible alternatives?  I currently use Ubuntu One as a backup service for my Documents folder and various other folders I deem important. Of course I have backups on an external hard drive as well, but nevertheless, I find Ubuntu One to be very useful. What I'm especially looking for is a cloud service that does not need a special folder (such as a dropbox or google drive folder); something that is able to integrate into my own file system and syncs just any folder I want to.   I am aware that this question is rather subjective, but I do guess many people who have used Ubuntu One are now in the dark. Can I use one Apple ID for Apple Music and another for iTunes & App Store? Let us suppose I want to use a shared Apple ID for logging into iTunes &amp; App Store, in order to share music and app purchases with a friend.  But let us also suppose that, despite this, my friend and I have very different tastes in music, so I don't want to share Apple Music playlists and "like" assertions with my friend. In other words, I don't want Apple Music to think I like the music my friend likes, and vice versa.  Is there a way that my friend and I can share an Apple ID for logging into iTunes &amp; App Store, but use different Apple IDs for Apple Music?  I suspect the answer is no, but I just wanted to ask. The cardinality of a language over a set of variables $V$ with $\#V= κ$ In predicate logic, to define a language, we consider the following $3$ sets:  (1) $V$, the set of variables;  (2) $F$, the sets of function symbols;  (3) $P$, the set of predicate symbols with their arities.   Now I am concidering about determine the cardinality of a language over a set with arbitary cardinality, $κ$(Note that $κ$ can be either finite, countablely infinite or uncountablely infinite ).  May I please ask:  If the cardinality of $V$, $\#V = κ$, what conditions on $V$ , $F$ and $P$ will give us a language over $V$, $F$ and $P$ with cardinality $κ$?  And may I please ask if it is the fact that if $\kappa$ is finite, then to get a language with cardinality $\kappa$ we need $(V+F+P)^{&lt;\omega}=(\kappa+F+P)^{&lt;\omega}=\kappa$, so we can never have a language of cardinality $\kappa$. I think it is something weird here. Am I wrong with something?  I had googled it but I have get nothing from websites, now I am confused. Could someone please help? Thanks so much!  EDIT: Latter I am told that in my course, the cardinality of a language refers to the set of expression instead of this of the set of strings. So now I need to consider further about when a string makes sense.  EDIT':Now I am considering that if we can find out a general way to determine the cardinality of expression, which may related to combinatorics. See this question:  Any help would be appreciate. Comparing signatures of apks I have two .apk files that are supposed to be different versions of the same app. What is the best way to check if they where both signed with the same key?  I want to make sure no mistakes were done and the newer version would be treated as an update of the same app. How can I test the quality of a RNG? On electronics.stackexchange we had  about constructing a True Random Number Generator. Since the method relies on noise, which isn't deterministic, the only way to test the quality of the RNG seems to be empirical. Not being a statistician I suggested to test a long bit sequence for normality, but I have no idea what outcome is acceptable and what isn't. For instance counting single bits I guess we have a thumbs-up for a 499500/500500 distribution, but when is the ratio too much skewed to be acceptable? Same for 2-bit and longer sequences. Of course, if testing for normality is a Bad Idea™, I'd like to hear it, including better alternatives.    edit Diehard was mentioned a few times, but I'm not sure this answers my question. The normality test should give a normal distribution, with better bell curve approximations for longer sequences. Diehard seems also to have tests which either should result in normal or exponential distributions. But my question remains: how do I judge the results? Just by looking at the curve and discern a bell curve in it? To get back at my first example, a 499500/500500 distribution is definitely OK, and a 950000/50000 distribution definitely is a no-no, so where does the switch-over happen? How do malloc() and free() work? For example,      I like chocolate, vanilla, and lemon and orange ice cream.    Indicating "lemon and orange" is a combined flavor, as an item in the list needing an initial and. What is the relationship between redshift and conformal time ?   For example in a paper i found:   taking $z_e = 3234 $ at the time of radiaton-matter equality yields the conformal time $\frac{\eta_e}{\eta_0} = 0.007$ and taking $z_E=0.39$ at matter-$\Lambda$ equality yields $\frac{\eta_E}{\eta_0}=0.894$ and setting redshift at decoupling $z_d=1089$ yields $\frac{\eta_d}{\eta_0} = 0.0195$  where $\eta_0$ is the present decoupling time.  Further some cosmological parameters are given as :  $\Omega_r = 8.36 \times 10^{-5}, \Omega_m = \Omega_b + \Omega_{dm} = 0.044 +0.226, \Omega_\Lambda = 0.73,  H_0=0.72$  Now how can i calculate all those $\eta_e, \eta_E, \eta_d, \eta_0$ from given redshift values and/or above parameters ? I searched whole of my text books trying to find an explicit relation for conformal time $\eta$ but all i got was $ \mathrm{d}t=a(t)\mathrm{d}\eta$. Any help would be very helpful. How to get Debian codename without lsb-release I am trying to create a script that requires me to print the debian codename so that I may echo it into the sources.list file.  I am trying to make this script work across any version of Debian, so I had hoped to set a bash variable of the release codename. This would be simple to do (with lsb_release -c), however our deployment images do not contain lsb_release by default - and with this script being required to fix the sources.list, installing lsb-release with apt-get would not be an option.  I have found numerous ways to get the release number and other info about the system, but cannot find a reliable place to get the codename.  Any ideas would be greatly appreciated!  (OS I am testing this with is Debian Squeeze) Imported CSV data is not displayed in QGIS I watched a simple video tutorial on how to accomplish it, but nothing shows up on my project when I add the layer. Even if I try zoom to layer, the screen just shows blue. I'm not sure if it has something to do with my Excel, computer, or program. I really need help as I am new to QGIS. (I just posted this, but it won't let me comment to people under that question any more) I have a layer of google hybrid, but when I do add the new layer it is at the top and checked transparency and everything. Its just not accepting the data I entered into the excel spreadsheet is my guess to what the issue is.  I have the spreadsheet with the name, longitude, latitude. Save as CSV In QGIS go to Layer &gt; Add layer &gt; Add Delimited Text Layer Upload the CSV Excel file Add  Nothing shows even tho there is a line in the layers (bottom left) showing that &quot;something&quot; is there but if I choose &quot;zoom to layer&quot; it changes to a blue screen I have a Base layer Google Maps hybrid, and an area of interest on Georgia GIS Point or discrete longitude and latitude columns? I see that the Point type is made to store geometric coordinates, however I don't see what problem it is trying to solve, or what advantages it offers over simply using two numerical columns. It's 16 bytes, so is it just an abstraction for two 8 byte floats? Or is it a string containing some kind of geohash that optimizes the performance of certain queries?  Let's say I want to get all the points for a specific viewport on a Leaflet map... with numerical columns representing latitude and longitude, I'd just filter for all the rows that have a latitude number between the N/S bounds and a longitude number between the E/W bounds, easy. I looked into using Point here, but the syntax is cumbersome and it seems to me like unnecessary overhead for development and for database performance... is it? Why does my Nikon D3100 give the error "Lens not attached" with a Vivitar 200 telephoto lens? Conveniently schedule a command to run later? What's a simple way to run a command, say, 8 hours from now? I can think of this way:  nohup bash -c "sleep 28800 ; ./mycommand.sh" &amp;   Is there a more "proper" way?