What does the (2) after Unix system calls names mean?
What does the number in parentheses shown after Unix command names in manpages mean?
How can I access cloth properties via python? I want to manipulate options like Disk Cache with python:    Any Ideas? Why is jumping into water from high altitude fatal? Order of automorphism group of cyclic group Let $G$ be a cyclic group of order $m$. What is the order of $\text{Aut}(G)$?  I want to know the proof as well (elementary if possible). I would still accept the proof if one answers with $m = p$, a prime. Or on top of that, I would accept the answer with extra assumption: $q \equiv 1$ mod $p$ with another prime $p$. Urgent Sydney transit visa question How to show that the spherical metric satisfies the triangle inequality? For $x,y\in \mathbb R^n$ define  $$d(x,y)={\|x-y\| \over \sqrt{1+\|x\|^2} \sqrt{1+\|y\|^2}}$$ Here $\|x\|$ is the euclidean norm of a vector. How to prove that $d$ (the spherical metric) is indeed a metric?     Progress so far:    $d(x,y)\ge 0$ is obvious. $d(x,y) =0 \iff \|x-y\|=0 \iff x=y$, so the positivity holds. $d(x,y) = d(y,x)$ is clear from the formula, so symmetry holds.    But I am having difficulties with the triangle inequality. Writing it out in coordinates leads to a complicated inequality with square roots all over the place in denominators. Is there a better way? How can I maintain open ssh connection and use it from shell scripts? Currently i invoke the following:  $ ssh me@host.com my_cmd   This is slow and not easy to automate safely. I would like to establish ssh connection once and have some script that will forward my commands to host.com and print output.  Is that possible ?  Adding my machine to authorized_keys is not an option for me and it wouldn't solve slowness issue. Continuous and bounded variation does not imply absolutely continuous I have a question about the pattern "turn &lt;something&gt; on &lt;somebody&gt;" :     Then he allegedly turned the body-building equipment on his 44 year-old wife, identified by sources as Feng Liang, and his elderly mother-in-law, Feng Kun Zaehng,77, the sources said.     I understand the phrase "*turn the gun on &lt;somebody&gt;", am not sure about "turn the equipment on &lt;somebody&gt;".  Could the example be wrong? Fermi in his lecture asserts:     The second law of thermodynamics rules out the possibility of constructing a perpetuum mobile of the second kind.   So, this means there can be no machine which just transforms all the heat energy gained by cooling surrounding bodies into mechanical work.  But how does actually the Second Law prohibit this?   The hot reservoir provides heat energy to the system. Does it cause a decrease in entropy of the universe(system + hot reservoir)? How? In order to receive heat wouldn't the system have to be cooler than the reservoir? If so, then entropy increases as the heat energy gets expelled from the reservoir at a higher temperature than the temperature the system receives the heat energy. Is it so?  I'm not getting how the Second Law nullifies the existence of this machine. Could anyone please explain how the Law prohibits the perpetual machine of the second kind? Proof that the One-Dimensional Simple Harmonic Oscillator is Non-Degenerate? I have seen many folks doing this  concluding that shadow from point A on the Moon can travel to point B on the Moon faster than light.  What I fail to understand here (and I am sure I am wrong), is nothing can travel faster than light. I also read about Relativity where Einstein stated that every event happening for you depends on how fast the light gets from where the event is happening to you.  This is my particular problem with this Moon shadow experiment. You cannot make a shadow travel faster than light, because in order for the "disappearance" of light to get to the Moon, it has to travel at light speed.  Here is one way to understand my point. Consider we shine a flashlight on Moon, like the guy in the linked video did, we move the finger across the face of the flashlight, before we moved the finger it was casting the shadow at Point A on Moon, after we finish moving our finger, the shadow is at Point B on the Moon.  When the finger reaches the end of it's moving length, the light waves that have left the flashlight before the finger reached there will have to hit Point B and it will take them a second and a half to get there, and another second and half for us to see that shadow on point B, which makes it 3 seconds + finger moving time for us to actually see the shadow at point B. That means shadow traveled (say) across the diameter of the Moon in 3 seconds.   So. about 3000 Km in ~3 seconds make it 1000 Km per seconds which is very tiny compared to the speed of light. How can these experiments conclude that Shadow could be made to travel faster than light? What is the obvious clue that I am missing here? Simple bijection $\mathbb N_0 \times \mathbb N_0 \to \mathbb N_0$ I'm looking for a 'simple' bijection $$ \pi \colon \mathbb N_0 \times \mathbb N_0 \to \mathbb N_0, $$  where 'simple' in this context means that it should be as easy as possible to define and it should be self-evident that said function is in fact a bijection. It's a quest for convenience - not minimal complexity in any rigorous sense.  Here are a couple of examples I came up with - none of which satisfy both requirements:   Let $\pi(m,n) = c(2^m3^{n+1})$, where $c \colon \{2^m3^{n+1} \mid m,n \in \mathbb N_0 \}\to \mathbb N_0$ is the order isomorphism (or in fact Mostowski collapse) of its domain under the natural ordering, Let $\pi(m,n) = \langle n,m \rangle$ - Gödel's pairing function, Let $\pi(m,n) = m \oplus n$ - the number resulting from '' $m,n$ (where we imagine both $m$ and $n$ as in infinite decks of cards whose $i$th element is labeled with its respective $i$th digit). ... Showing a tensor is not a simple tensor I have been trying to make a short clip of a bullet hitting a wine glass with wine in it, but I keep running into the same problem with the add-on. Every time I have used it the result has left me with at least a partial box being generated as several of the fractured pieces.  I have tried subdividing and/or adding a sub-surf modifier but the result only changes where the large distorted fragments end up. I have been having trouble with this for quite some time and I would greatly appreciate any help. 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? How many nonnegative integer solutions are there to the pair of equations  \begin{align}x_1+x_2+\dots +x_6&amp;=20  \\ x_1+x_2+x_3&amp;=7\end{align}  How do you find  non-negative integer solutions? Enumerate in multicols how to move the last element upwards Code: \documentclass{article} \usepackage[a5paper]{geometry} \usepackage{multicol} \setlength{\parindent}{0cm} \begin{document} \begin{multicols}{2}   \begin{enumerate}   \item text 1   \item text 2   \item text 3   \item text 4   \item text 5   \end{enumerate} \end{multicols} \end{document}  Gives this:  How to move &quot;text 5&quot; upwards adjacent to &quot;text 4&quot;? When quoting something said by someone else, should I use a comma before the quote? Suppose I quote the definition given in a dictionary. Am I correctly using the the punctuation marks in the following sentences? (I am using them in the way I think correct in American English.)     One of the meanings of cat is, "a small animal with soft fur that people often keep as a pet."        A cadet is, "a young person who is training to become an officer in the police or armed forces."   Should I use a comma only when I explicitly quote somebody?     Groucho Marx once said, "Although it is generally known, I think it's about time to announce that I was born at a very early age."   Should I use a comma in this case too?     As Groucho Marx said,            No one is completely unhappy at the failure of his best friend.      On Comma Sense, A fun-damental guide to punctuation (Richard Lederer and John Shore), I read the following about using the comma:     Use commas to set off complete quotations:           The great general George S. Patton once said, "No, no—the war is this way, you idiots!" This is NOT an installation problem question. I've had both op sys working fine side-by-side for a couple of weeks now. I'm using Ubunutu 12.04 64-bit.  This morning when I tried to switch from Win8 to Ubuntu, it just rebooted into Win8. No grub screen whatsoever. This is the 3rd machine I've had dual-booting &amp; have never seen this, but then Win8 is a 1st for me &amp; has thrown some pretty awesome blocks in the path to get to here. Atrocious op sys...  I'm assuming the ASUS updater did this yesterday. (ASUS R503U)  So, do I just put the Ubuntu disk in &amp; reinstall grub? Rewrite Sharepoint URL (Sharepoint 2013) I'd like to rewrite all my site urls in the way the the user can't figure out the exact name of the the page his viewing. let's say that my site is "www.justarandomsite.com"  and may page is "page.aspx" I' like to have instead of "www.justarandomsite.com/pages/page.aspx" sothing like this: "www.justarandomsite.com/skdhfjksdgfjksdgfjdsgvdjhsgfjdsdsjfgkdsjgfkdsgfjdsgfjkdsg"