My terminal is set to UTF-8. If I type this:  echo -n 'ýá' | xxd   I can see this output:  00000000: c3bd c3a1   Which is fine. Now I would like to remove the 'ý' character from the string, so I use:  echo -n 'ýá' | tr -d 'ý' | xxd   But the result will be:  00000000: a1   The tr removes also the next c3 byte, but that is part of the 'á' character. Why is working this way? Is this a bug? Or should I set something?
I'm trying to remove some characters from file(UTF-8). I'm using tr for this purpose:   tr -cs '[[:alpha:][:space:]]' ' ' &lt;testdata.dat    File contains some foreign characters (like "Латвийская" or "àé"). tr doesn't seem to understand them: it treats them as non-alpha and removes too.  I've tried changing some of my locale settings:  LC_CTYPE=C LC_COLLATE=C tr -cs '[[:alpha:][:space:]]' ' ' &lt;testdata.dat LC_CTYPE=ru_RU.UTF-8 LC_COLLATE=C tr -cs '[[:alpha:][:space:]]' ' ' &lt;testdata.dat LC_CTYPE=ru_RU.UTF-8 LC_COLLATE=ru_RU.UTF-8 tr -cs '[[:alpha:][:space:]]' ' ' &lt;testdata.dat   Unfortunately, none of these worked.  How can I make tr understand Unicode?
In MySQL, how do I get a list of all foreign key constraints pointing to a particular table? a particular column? This is the same thing as , but for MySQL. How do I configure Nautilus to open at my Documents folder instead of my home folder?  I've scoured this site and found answers instructing users to edit the /usr/share/applications/nautilus.desktop file, replacing %U with the path to the desired default directory. I've edited all the variants of nautilus.desktop in the said directory, but none of the edits has an effect. I've checked all the files after editing them to make sure that I saved the edit effectively, and all look good to me.   I've edited every file to read as follows:  Exec=nautilus --new-window /home/judy/Documents   I've also edited the org.gnome.Nautilus.desktop file, just to be sure, with no joy.   I'm running Ubuntu 15.10.  Note: if I enter nautilus /home/judy/Documents from the command line, Nautilus properly opens in the desired directory.  Is there a simple way that I can configure an icon in the launcher bar to run this command and have the Nautilus icon that looks like a metal file drawer?  Thanks. I'm pulling my hair out over this one. I am not asking about the two factor authentication process where the user needs to enter both a password and a one-time-password.  Gmail recently (I don't know from when exactly) changed their login process which is depicted in the following screenshot:     So, the new steps are as follows:   Enter email   Click Next  Enter password   Click Sign In    as opposed to the previous and usual way of logging in:   Enter email and password   Click Sign In    Isn't the new process non-user friendly requiring extra user interactions?  Since, Google does not usually make UX blunders can you explain the reasoning behind the new process? I'm looking for details like user interaction simplicity or any other hidden advantages.  Note: The question  doesn't cover the reason behind the change while Mervin Johnsingh's answer cites Google's reason. Resizing an Image without losing any quality Why do mirrorless cameras have quicker autofocus than SLRs using live view? I have my CIFS setup in fstab and they are working as they are supposed to on boot. They mount as they should and work for a while. Out of nowhere it seems (could be after unlocking machine etc) I get "Host is down" error trying to access it. I have multiple and they are all down. They are also shared from the same server. At this time i check on a windows computer and an outdated 14.04 machine and they are up and functioning as they are supposed to. After clicking around on the shares in nautilus and getting repeat errors they will just start working again. To access a share that is "down" takes about 2-3min of randomly clicking different mounts and going back to the first one when automagically it shows the data in the mount point.  I do not have this problem on 14.04 machines that have not been updated in a while. All of those machines are fully functional and the CIFS never go "down". On 16.04 they were not a problem until more recently.  I have made sure to update every other day and have cleaned old linux headers (in hind sight i probably should have reverted). I do this because im begging for a fix to just appear but its been weeks of battling CIFS mounts without any solution. Scale Insetted Characters to Plot $11$ out of $36$? I got this by writing down the number of possible outcomes ($36$) and then counting how many of the pairs had a $6$ in them: $(1,6)$, $(2,6)$, $(3,6)$, $(4,6)$, $(5,6)$, $(6,6)$, $(6,5)$, $(6,4)$, $(6,3)$, $(6,2)$, $(6,1)$. Is this correct? Should I ask questions I already know the answer to and answer them myself? More examples of Simpson's Paradox, barring the ones on Wikipedia, Titanic, and delayed flights. I hope someone may know fresh examples of  for use in my statistics courses.  The examples I've been using are fine, but I'd like to have some new ones.  I'm familiar with the ones on the Wikipedia page: the gender bias lawsuit at Berkeley, batting averages, mortality rates among low birth babies, party voting on the Civil Rights Act, and success rates of kidney stone treatments.  I'm also familiar with the example of survival rates on the Titanic and the one about delayed flights at America West vs. Alaska Airlines.  These are all good ones, but, like I said, I'm looking for more. Does anybody know any others?  For those who aren't familiar with it, Simpson's paradox is essentially a property of unreduced fractions: It's possible to have, simultaneously, $$\frac{a_1}{b_1} &lt; \frac{c_1}{d_1} \text{ and } \frac{a_2}{b_2} &lt; \frac{c_2}{d_2}, \text{ but } \frac{a_1 + a_2}{b_1+b_2} &gt; \frac{c_1+c_2}{d_1+d_2}.$$   For example, $\frac{1}{3} &lt; \frac{34}{100}$ and $\frac{66}{100} &lt; \frac{2}{3}$, but $\frac{67}{103} &gt; \frac{36}{103}$.  It can be hard to spot this happening in a given real-world scenario. Extend or remove Data Explorer timeout I know that we don't have automatic login for the Data Explorer, but what's with the automatic timeout/logout?  There have been times that I am logged into the site, maybe I walk away for a little bit, and I come back to being logged out.    Is there a reason for logging us out of Data Explorer?  If so, is it possible to either remove the timeout or extend the period of time before timeout? What is the meaning of ./ before a given path? not able to execute multiple commands on multiple linux machines? Help with this trigonometry problem What's the difference between the server version and the desktop version? Seems that I just proved $2=4$. Solving $x^{x^{x^{.^{.^.}}}}=2\Rightarrow x^2=2\Rightarrow x=\sqrt 2$.  Solving $x^{x^{x^{.^{.^.}}}}=4\Rightarrow x^4=4\Rightarrow x=\sqrt 2$.  Therefore, $\sqrt 2^{\sqrt 2^{\sqrt 2^{.^{.^.}}}}=2$ and $\sqrt 2^{\sqrt 2^{\sqrt 2^{.^{.^.}}}}=4\Rightarrow\bf{2=4}$.  What's happening!? Do the laws of physics evolve? Hubble's constant $a(t)$ appears to be changing over time. The fine stucture constant $\alpha$, like many others in QFT, is a running constant that varies, proportional to energy being used to measure it. Therefore, it could be agued that all running constants have 'evolved' over time as the Universe has expanded and cooled. Both the local and global curvature of the Universe changes over time implying that so too does the numerical value of $\pi$. All these things are however constants (well, let's say parameters since they are not really 'constant'.)   In  with astronomer Sir Fred Hoyle, Feynman said "what today, do we not consider to be part of physics, that may ultimately become part of physics?" He then goes on to say "..it's interesting that in many other sciences there's a historical question, like in geology - the question how did the Earth evolve into the present condition? In biology - how did the various species evolve to get to be the way they are? But the one field that hasn't admitted any evolutionary question - is physics."  So have the laws of physics remained form-invariant over the liftetime of the Universe? Does the recent understanding of the aforementioned not-so-constant constants somehow filter into the actual form of the equations being used? Has advances in astronomical observations, enabling us to peer back in time as far back as the CMB, given us any evidence to suggest that the laws of nature have evolved? If Feynman thinks that "It might turn out that they're not the same all the time and that there is a historical, evolutionary question." then this is surely a question worth asking.  NB/ To be clear: this is a question concerning purely physics, whether the equations therein change as the Universe ages, and whether there is any observational evidence for this. It is not intended as an oportunity for a philosophical discussion. How do you create product mock-ups? How can I edit my network profile independently? My oldest account on the network is Area 51, followed by Mi Yodeya.  I recently filled out the "about me" section on Mi Yodeya (but nowhere else) and did not choose the "update all sites" option because my blurb is pretty specific to that site.  I intended to have that blurb on exactly one site.  I was surprised tonight to discover that that blurb is now on my network profile, where I see no "edit" link.  Am I stuck with either having a site-specific blurb as my network blurb (because it's my first non-Area-51 site) or rewriting it to be more general?  Or is there some way that I can independently edit the network profile?  (Or designate a different site as the default?)   shows that someone else had this problem too, but I'm asking for support, not for a new feature, so I'm asking this separately. Let $M$ be the manifold of real positive definite $n \times n$ matrices, define a mapping $i:A \to \sqrt A$ (where $A\in M$ and $\sqrt A$ means the unique positive definite square root of $A$). Please show that $i$ is smooth.