How can I use awk to count the total number of input lines in a file?
I'm sure there are many ways to do this: how can I count the number of lines in a text file?  $ &lt;cmd&gt; file.txt 1020 lines
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. Emmy Noether's theorem in simpler terms I'd like to understand  and its contents as to what it implies in a bit simpler terms. I am familiar with mathematics unto Calculus 1,2,3 and some linear algebra and group theory. I am familiar with that for each symmetry there is a conservation law.    Now is there a one-one correspondence between these two always? What about laws like conservation of charge?  And conservation of energy?  And conservation of mass?  Considering our view of nature was changed as Special Relativity was introduced and thus, what earlier the theorem would have asserted as mass and energy to be originating from different symmetries then how did we reconcile these two as just one symmetry? The following is an excerpt from a New York Times article of April 6.     “Tonight, I ordered a targeted military strike on the air base in Syria from where the chemical attack was launched,” Mr. Trump said in remarks at his Mar-a-Lago estate in Florida. “It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons.”    Shouldn't that "from where" be either "from which" or else just "where" without "from?" Does there currently exist a free online service that accepts a file, hashes it, takes an authoritatively chosen timestamp (from one or more time services), signs these and sends this signed message back? E.g. a digital notary, but only with regards to the timestamp and not the validity of the content as legal notaries might be obligated to guarantee.  Such a service might have an extremely simple API: Simply wget http://service/&lt;checksum&gt; and receive a signed message containing one or more timestamps and the checksum. The emphasis would be on the type of authority who might make such a service.  Edit: Although the original question did not emphasise the following, the Bitcoin-based timestamping services provided below do not rely on one authority, but rather the entire Bitcoin network. They can be seen as tamper-proof and verifiable without the help of the service that helped you sign it! Reading a bit about recent Monica Cellio related posts, I am afraid that I may be using a language that is a lot like English, but might not be the Stack-Exchange-approved version of English. For example, my English has had a certain gender-neutral pronoun in living use for centuries. That pronoun is used throughout the literature written in this version of English. It is used in the English I was taught as a grammar school student and later as a graduate student working on a master's thesis. I believe that this English is good enough to communicate about topics relevant to the various Stack Exchange sites.  The last thing I want from Stack Exchange is to be booted out because I slip up and accidentally use the language that has served me so well for a lifetime.  The topics discussed on Stack Overflow (I almost referred to it as a "sister site;" would that have been allowed? "mother site?" Good thing I didn't?) are often centered on languages which have formal descriptions.  Where is the formal description of the language that is to be used on Stack Exchange?     Strive not with a man without cause, if he have done thee no harm.      He shall die without instruction; and in the greatness of his folly he shall go astray. Find all real numbers $x$ for which $$10^x+11^x+12^x = 13^x+14^x.$$   I thought about taking the logarithm of both sides, but didn't see how that would help. How can we make the equation simpler? Is it just for me, or has the privilege to review new posts and late answers changed for everyone?  I recently started being more active in reviewing, but the rep requirement just shot up and I can not review anymore? The rep requirement has shot up to 500. Is this just for me, as a 'process", or has it been changed site wide? If moderators can view , can we see comments we've deleted? We can see our deleted answers, but why not our deleted comments? Summer in Saint Helena The Winter Bash site is located at http://winterba.sh/.  Only one problem:   . Saint Helena is in the Southern Hemisphere. It's Summer in Saint Helena.   So shouldn't it be the Summer Bash? Don't forget our Aussie/Kiwi/South African/Southern Brazilian/Argentine/Uruguayan/Zimbabwean/Swazi/Tokelauan/Tuvaluan/Pitcairn Islander/ friends! What is the difference when you say "get off of something" and "get off something"? About integer factorization When I try to sculpt with dyntopo on a sword it creates really weird results while it works just fine on other meshes. Any idea what causes this? How to create a virtual audio device and stream audio input with it Here's my concrete problem:  I am broadcasting a game via XFire and it uses the Windows audio device to capture any audio I receive. As I am broadcasting, other users who watch the video stream are communicating with me over Skype, and they hear themselves back within the video stream and it is entirely logical since I am broadcasting the audio I hear.  What I want to do is create another audio device within Windows and redirect (pipe) ONLY the audio input from that game and not the input reveived from Skype. I would then tell XFire to use that newly created "virtual" audio device to broadcast and therefore my partners won't hear themselves back.  Is it possible to create another audio device and redirect only wanted input streams to it? So, floor is a function that converts a real number to an integer. It rounds down. This makes sense; however, what about complex numbers? I know that depending on the number, it can be split linearly. However, I do not know what $\lfloor i\rfloor$ equals. Is there a clearly defined definition of $\lfloor i\rfloor$? What do you call a person who started something that is later followed by everyone? I am looking to build a camera trap for wildlife viewing, able to capture pictures (or even videos) in decent quality to be able to identify distinct features. I do however need to be able to see the pictures in real time, so the camera would need some sort of wireless connection to a receiving device such as a phone.  I thought of using an FPV setup as used in drone racing, but the quality and range seems to be quite low, and the strengths of an analog signal seem to be latency and fps, which are both not important to me. It would be nice to have some sort of digital signal to be able to do some editing, such as storing pictures. It would also be cool to connect several cameras to one device.  Are there any solutions to this problem? Would a raspberry pi/arduino setup work in some way? Thanks! Trying to remap my left SUPER key (also called WINDOWS key) to left or right CONTROL key, with xkg Plotting logarithmic regression with gnuplot using PGFPlots I have the data in 001.csv below that I want to plot. I need two plots: one showing the data and another one showing logarithmic regression. I have no problems plotting the line for the data (and also adding a linear regression line) but I just can't manage to get a logarithmic regression line in there. As far as I understand, I need to use gnuplot for this but unfortunately I can't make it work. Any help would be much much appreciated.  Cheers,  Cem  %%%%%%%%%%%%%%%%%%%%%% %This is my data:  \begin{filecontents}{001.csv}     1990 275     1991 187     1992 249     1993 177     1994 212     1995 303     1996 323     1997 364     1998 461     1999 427     2000 683     2001 553     2002 571     2003 682     2004 585     2005 608     2006 609     2007 643     2008 719     2009 545 \end{filecontents}  %%%%%%%%%%%%%%%%%%%%%% %This is my plot for the data:  \begin{tikzpicture} \begin{axis}[     axis on top=false, axis x line=middle, axis y line=middle,     xlabel={\footnotesize Year},     ylabel={\footnotesize Frequency count},     xmin=1975, xmax=2009,     ymin=0, ymax=900,     xtick={1980,1985,1990,1995,2000,2005,2009},     ytick={0,100,200,300,400,500,600,700,800},     legend pos=north east,     legend style={font=\fontsize{6}{5}\selectfont},     ymajorgrids=true,     xmajorgrids=true,     grid style=dashed,     /pgf/number format/.cd,     1000 sep={}     ]  \addplot[     smooth,tension=0.9,color=blue,mark=diamond         ] table {001.csv};  %Somewhere here I need a logarithmic regression line.  \end{axis} \end{tikzpicture}  %%%%%%%%%%%%%%%%%%%%%% Suppose A is a 3*3  symmetric matrix s.t.  $$\begin{pmatrix} x &amp; y &amp; 1 \\   \end{pmatrix} A  \begin{pmatrix} x  \\  y\\ 1\end{pmatrix}  = xy -1 $$  let p be the no. of positive eigen value of A and q = rank(A)-p, then p=? q=?  what matrix A should be I can't find?? If a linear operator has an adjoint operator, it is bounded