Control sequences in setting PS1 for xterm This is from .bashrc file: # If this is an xterm set the title to user@host:dir case &quot;$TERM&quot; in xterm*|rxvt*)     PS1=&quot;\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1&quot;     ;; *)     ;; esac  I was wondering what does \[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\] do? I know \[...\] are non-printing characters, but what does this actually do?
Where can I find a complete reference for the $PS1 variable? The default PS1 variable on my machine (Kubuntu 13.10) is this:  \[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\u@\h:\w\$   I'm looking for a reference for how the $PS1 variable works that, at a minimum, allows me to understand the above PS1 variable.
How to derive addition of velocities without the Lorentz transformation? Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of    $$w~=~\dfrac{u+v}{1+uv/c^2}$$   without Lorentz transformation? Using just the constancy of light speed. How is the passage of time handled in Pokemon? Error: 'else' without 'if' error while loading shared libraries: libssl.so.1.1 (and libcrypto.so.1.1) As you can see I'm missing libcrypto and libssl files. I locked out myself from my server after running apt-update and apt-upgrade, I'm running this from web console, because ssh nor any other program won't work because of missing SSL files.  I tried removing and installing apt install openssl so did libssl-dev and/or compiling own openssl from a distro. None of these create the needed .so files, I ran locate, those files are not present anywhere on the server. There's also libssl1.0.0 which cannot be reinstalled and removing it would cause removal of 700MB of packages that would literally kill server and delete all data. Should a toggle button show its current state or the state to which it will change? Between vs. Among - "Difference [between | among] one thing and other things." Consider the following two versions of a question:1   Version 1: What is the difference in meaning between "[to be] not invited" and similar negation forms?  Version 2: What is the difference in meaning among "[to be] not invited" and similar negated forms?    Personally, I think Version 1 might subtly suggest a Star Topology (see below) with the target sentence "[to be] not invited"at the center.  And Version 2 might subtly suggest a more free-form comparison like the Mesh or Fully Connected, with the target sentence simply "one among many":   Between approx equal "Star" and among approx equal "Fully Connected"?  Don't get me wrong: I do think this is quite subtle, not always applicable, and I don't think anyone would intuit such a "network topology" meaning without further explanation.   So the main question is, are both grammatically correct?  If yes, is there a semantic difference to choose one over another, perhaps as I suggested?  Or does the plurality aspect of between and among trump other semantic and stylistic issues?    1. In my question , another user provided a very helpful edit. However, the change of the word between to among prompted this question. $\bigodot=?$ for $(\sqrt 2) ^ \sqrt 3 \bigodot (\sqrt 3) ^ \sqrt 2$ where $\bigodot is \lt or \gt$ $\bigodot=?$ $(\sqrt 2) ^ \sqrt 3 \bigodot  (\sqrt 3) ^ \sqrt 2$  where $\bigodot is either \lt or \gt$   In other words, which one is larger $(\sqrt 2) ^ \sqrt 3$ or $(\sqrt 3) ^ \sqrt 2$? The best I could do was ending up with $\sqrt \frac {3}{ 2} = \frac {\ln 3}{\ln 2}$  side question : is there a symbol like encircled $?$ for when what we are trying to find is the correct order symbol like one of $\lt,\leq,=,\geq , \gt $ ?  Hopefully using just juxtopisition of symbols without resorting to real analysis. is it possible to do with precalculs algebra? How to estimate camera sensor size? I am using a smartphone for capturing photos and I need to estimate the camera sensor size (mm*mm). I have the resolution (in pixels) and the focal length (in pixels). I can also measure the size of any stationary object and its distance w.r.t the lens. Basically, I don't have a pixel-to-mm metric for any of the above parameters that I can use. Is there any way I can calculate that to estimate sensor size? Expressing the area of the cross section of a cylinder I was able to solve similar questions where a triangle was involved, but this one has had me looping and pondering on it for the past week.  The Condition: Let $r$ be a positive constant. Consider the cylinder $x^2+y^2\leq r^2$ and let C be  part of the cylinder that satisfies $0\leq z\leq y$.  The questions:  (1) Consider the cross section of $C$ by the plane $x=t(-r\leq t\leq r)$ and express its area in terms of $r,t$  (2) Calculate the volume of $C$, and express it in terms of $r$.  (3) Let $a$ be the length of the arc along the base of the circle $C$ from the point $(r,0,0)$ to the point $(r cos\theta,r sin\theta,0)(0\leq\theta\leq\pi)$. Let $b$ be the length of the line segment from the point $(r cos\theta, r sin\theta, 0)$ to the point $(r cos\theta, r sin\theta, r sin\theta)$. Express $a$ and $b$ interms of $r,\theta$  (4)Calculate the are of the side of $C$ with $x^2+y^2=r^2$, and express it in terms of $r$.  Here are the expected answers(which I keep failing to get to):  (1) $\frac{1}{2}(r^2-t^2)$  (2) $\frac{2}{3}r^3$  (3) $r\theta$ and $r sin\theta$  (4) $2r^2$ Move every file that is not a directory How can I add an application to the GNOME window manager? The GNOME on-board documentation covers only the things anyone can easily guess. I have an application for that I can only start from the command line. Not that I mind using a terminal but ...  Anyway, how do I add the command (and preferably a nice logo) to GNOME WM? If/Else with Selenium IDE - when confirmation message comes up I have a scenario, in case of the user registration successful, it will display a success message on the next page otherwise an error message shows on the same page. How to automate the test case to return as passed if it is success and failure in case of error message comes up.  Please help me out here. I have been given a Bode plot of a low pass filter, and tasked with essentially reversing the effects by using a high pass filter. I have solved for the transfer function which is the first equation, and I am assuming the inverse transfer function will give me the information I need to construct the high pass filter. I know the values for \$z\$ and \$p\$. Is there a method given any transfer function to realise the circuit elements required? $$H(s) = 0.17\frac{s-z}{s-p}$$ $$H(s)^{-1} = 5.88\frac{s-p}{s-z}$$ How can I know if a branch has been already merged into master? I have a git repository with multiple branches.   How can I know which branches are already merged into the master branch? I usually prefer to fix a Linux system than to reinstall from scratch. My computers have seen many distribution upgrades and a list of PPAs or third-party repositories. APT usually makes sure that everything works in the end. However, the fact that the package manager thinks that all required packages are 'installed' does not guarantee that all the files are present on the file system.  Such a such situation may occur if you have to work-around dependency problems with dpkg --force-*. One could also reproduce such a situation by deleting a file from /usr as root.  Is there a simple way to verify whether all files belonging to an installed package are present?  If a such a problem package is found, aptitude reinstall fixes the problem. Focal length of an ellipse and related results The equation $X^{n} + Y^{n} = Z^{n}$ , where $ n \geq 3$ is a natural number, has no solutions at all where $X,Y,Z$ are intergers. Rounding up to next power of 2 I want to write a function that returns the nearest next power of 2 number. For example if my input is 789, the output should be 1024. Is there any way of achieving this without using any loops but just using some bitwise operators? Low wifi signal in 14.04 LTS Is there a way to "rescue" mesh that has very bad topology?