#!/bin/bash  for a in ./*.flac; do   ffmpeg -i "$a" -qscale:a 0 "${a[@]/%flac/mp3}" done   I found this script a few days ago to convert all FLAC files in the current directory into the MP3 format.  What I don't understand here is the "${a[@]/%flac/mp3}" part. I think it replaces the ending flac with mp3 for the current filename. But what eactly does the [@] part do? Is it a regular expression?
I'm quite confused about the following regular expressions I found in a shell script:  ${0##*/} ${0%/*}   How do they work?
Light Presets .exr I would like to install light presets for Blender to automate my lightning in my scenes. I have some .exr files (from Greyscalegorilla) but I don't know how to do it on Blender to make it work. Can someone help me? Thank you Why doesn't Neo teleport at random? The runabouts in Deep Space Nine sometimes have additional equipment on their backs; this is a screenshot from S02E15 (Paradise), showing the Orinoco in the background with the unknown equipment &amp; the Rio Grande in the foreground with a clean configuration:  What is the equipment &amp; why is it only sometimes present? In TeX, how is computing zero sign written with slanted vertical line on it? By looking at an integral and bounding the error? Consider an isosceles triangle. Let r be the radius of the circumscribed circle and p be the radius of the inscribed circle. Prove that the distance d between the centers of these two circles is $$d = \sqrt{r(2p-r)}$$ In the Breusch-Godfrey test we use a model  $$ e_t = \varepsilon_t + \beta_1 \varepsilon_{t-1} + \dots+ \beta_p \varepsilon_{t-p}. $$  If we reject the null hypotesis of no serial auotocorrelation of the error, it means that the residuals follow an auto-regressive model of order ($p$).  If I want to avoid this problem, I must add a certain number of lags of the response variable $y$ as regressors in the original model. However, in some cases this method is not useful.   Are there other options to consider? Suppress a biblatex field in only one of split bibliographies? I am aware of \clearfield, \clearlist etc (cf. ) - but I'm really not sure how to apply it in this context:  Say you have a split bibliography (i.e. several calls to \printbibliography in one document). How can you filter a specific field in a bibliography item - but only in one bibliography (i.e. only in one call to \printbibliography)?  For instance, in the MWE below (compiles with pdflatex test.tex &amp;&amp; biber test &amp;&amp; pdflatex test.tex &amp;&amp; pdflatex test.tex), let's say I'd like to filter urldate (i.e. urldate is not typeset) only in the first bibliography - but for the second one, the original/default behavior should be restored (i.e. urldate is typeset). How to I do that?  \documentclass{article} \usepackage{filecontents} \begin{filecontents*}{\jobname.bib} @online{ctan,   title        = {CTAN},   date         = 2006,   url          = {http://www.ctan.org},   subtitle     = {The Comprehensive TeX Archive Network},   urldate      = {2006-10-01},   label        = {CTAN},   langid       = {english},   langidopts   = {variant=american}, } @misc{google,   title        = {Google},   date         = 2007,   url          = {http://www.google.com},   urldate      = {2007-10-01}, } @misc{hotmail,   title        = {Hotmail},   date         = 2008,   url          = {http://www.hotmail.com},   urldate      = {2008-10-01}, } @misc{yahoo,   title        = {Yahoo},   date         = 2009,   url          = {http://www.yahoo.com},   urldate      = {2009-10-01}, } @misc{aol,   title        = {AOL},   date         = 2010,   url          = {http://www.aol.com},   urldate      = {2010-10-01}, } @misc{altavista,   title        = {AltaVista},   date         = 2011,   url          = {http://www.altavista.com},   urldate      = {2011-10-01}, } \end{filecontents*} \usepackage[utf8]{inputenc} \usepackage[backend=biber,defernumbers=true,style=ieee]{biblatex} \bibliography{\jobname}  \begin{document}  \section{Section 1} \begin{refsection}  Citing some stuff here: first \cite{ctan}, then \cite{google}, and finally \cite{hotmail}.  \printbibliography[sorting=none,section=\therefsection,resetnumbers=true]  \end{refsection}  \section{Section 2} \begin{refsection}  Citing some stuff here: first \cite{yahoo}, then \cite{aol}, and finally \cite{altavista}.  \printbibliography[sorting=none,section=\therefsection,resetnumbers=true]  \end{refsection}  \end{document}   Output: Standard error of a ratio I have a linear regression and two estimates, say A and B and their standard errors. I need to find the standard error of a ratio A/B [or A/(1-B)].  I guess the main problem is that I don't know the correlation between A and B. I also guess that makes this unsolvable, since the correlation plays a major role. Is this correct?  If I knew it, what would be the way to calculate the standard error? I was googling unsuccessfully.   I've created Aura components without any problem, but I can't figure out how enabled this:     I'm trying to enable that feature in a Dev Winter 15. What is a comprehensive definition of Philosophy? Alternatively, is it impossible to define Philosophy? This is a pseudo- question, but it seems like it belongs here. Exactly what the name entails. The function $2^n-1$ I see largely tends to generate primes when $n$ is prime. However, a week ago I heard that this was horribly false. Please show me a disproof. If I look through the microwave window I can see through, which means visible radiation can get out. We know also that there is a mesh on the microwave window which prevents microwave from coming out.  My question is how does this work? how come making stripes or mesh of metals can attenuate microwave radiation yet allow visible radiation?  Looks like an electrodynamics problem to me with periodic boundary conditions (because of the partitions on the microwave oven window). Is it discussed in any textbook? How to find the running network services and the port and user I want to find a list of all network services running on my system, including details of the port and services and the users. I know that I need to use netstat, ps and fuser. but I don't know how to write the command. Do I need to write a shell script to find all of them? or I can use in a line of commands? Thanks for your help. Space ship manned by only AI returns home to a different earth, back in time I read this short story 30 years or more ago.  A space ship is returning home to Earth from a battle. There are no people on board this ship, only an AI and the ship's computer. When the ship tries to contact Earth it gets no immediate response. The ship attempts to make contact for some time and then is successful with Houston Control (I think).  The AI discovers that it is on a different Earth from the one it is from and that it has also traveled back in time. (The enemy the fleet that it fought still exists).  The space ship comes from an Earth were the Greek empire did not get destroyed.  In the end the AI crashes the ship on the Capitol and gets destroyed, but the computer survives so that the human race has the knowledge of how to build ships and defend against the enemy.  Does anyone know the name of this story? Blocking web sites with Windows Firewall Is it possible to use Windows Firewall to block specific web sites for all browsers? Finding a pair of functions with properties I need to find a pair of functions $f$, $g$ such that    $f$ is not differentiable at  $x = 0$ $g$ is not differentiable at $f(0)$ $g \circ f$ is differentiable at $x = 0$   I've tried a lot of functions but just can't seem to find ones that work. Any help would be appreciated, thank you. How can I copy coverart from flac to opus with ffmpeg I am trying to convert some flac files which all have coverart embedded to opus with ffmpeg. All but the coverart gets copied over just fine, but I find myself unable to move the cover over as well. Tried all sorts of -mapmetadata stuff I could find so far, but no luck, the result is always missing the coverart.  While the original .flac reports to have a video stream with the coverart  Duration: 00:02:53.51, start: 0.000000, bitrate: 910 kb/s    Stream #0:0: Audio: flac, 44100 Hz, stereo, s16    Stream #0:1: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 500x500 [SAR 1:1 DAR 1:1], 90k tbr, 90k tbn, 90k tbc   the created opus files does not have any graphics:  size=    2815kB time=00:02:53.51 bitrate= 132.9kbits/s speed= 104x video:0kB audio:2793kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.811556%   I tried -vcodec copy, -mapmetadata 0, -mapmetadata 0:s:0 so far, with no luck. Doesnt seem to have anything todo with opus, as I have the same problem converting to aac.  So is there a way to get the cover out of the flac file and move it over to the new file in on go using ffmpeg, or do I have to extract it first and then glue it back again later to the new file with extra commands? When approximating a posterior using MCMC, why don't we save the posterior probabilities but use the parameter value frequencies afterwards? What exactly is nullptr?