When I run this…  echo "              fdsfsd dsfsdf    "     I really get the output of all these lines.  However, if I use this output as an argument for echo again…:  echo "$(echo "    fdsfsd dsfsdf    ")"   …I do only get the leading new lines, not the trailing ones:  (4 empty lines)       fdsfsd dsfsdf   So: Why does this happen? (Note I explicitly quoted the output of the $(), so I thought that would prevent such things.) And how can I prevent this?  (tested with zsh)  BTW, same result if I use printf instead of echo – although the former obviously always misses the last line break echo would usually add.
As per the following example, and as in  In bash, where has the trailing newline char gone?, I want to know "why" it happens    x="$(echo -ne "a\nb\n")" ; echo -n "$x" | xxd -p  # Output is: 610a62  # The trailing newline from the 'echo' command #   has been "deleted" by Command Substitution   I assume there must be some very significant reason for a shell action, namely Command Substitution, to actually delete some data from the command output it is substituting... but I can't get my head around this one, as it seems to be the antithesis of what it is supposed to do.. ie. to pass the output of a command back into the script process... Holding back one character seems weird to me, but I suppose there is a sensible reason for it...  I'm keen to find out what that reason is...
Eevee - Light inside a bulb lamp not passing through glass Using Eevee, I'm trying to simulate a light bulb. I have a sphere with glass material and inside it, I have a Point light. But the light is not passing through the glass:  However, if I disable the sphere object, the light is working:   How to make the light inside a bulb lamp pass through glass (using Eevee)? Here my test project: To select a child node in jQuery one can use children() but also find().   For example:  $(this).children('.foo');  gives the same result as:  $(this).find('.foo');  Now, which option is fastest or preferred and why? There seems to be more than a few computer science/programming Stack Exchange networks (is that the correct term?). Stack Overflow, being the first, has by far the most users, questions, and answers.  What is the reasoning for creating the others, and are there clear guidelines for which kinds of questions should be posted? I can see a large amount of potential overflow, many cases of people not getting a good answer to their question, because the person who has the answer isn't browsing that particular network at the moment.  I understand that they were probably created for organizational purposes, but wouldn't it almost make more sense to just have them as categories under Stack Overflow, keep them separated but still connected, instead of making people have to create multiple 'account's, one for each network?  I am sure there was a very good reason to break them up, but as someone that is new to SE, it can be somewhat intimidating to decide which one to post in to ensure you get a good answer. For example, if I am a computer science student, my first instinct might to be to post in the computer science network, until I see that it literally has 1% of the users as the Stack Overflow network, which still seems to be for programming/computer science related questions.  So my second instinct would then to be to post it into the Stack&nbsp;Overflow site on the basis that I have a significantly higher chance of my question being seen and getting a good answer. Then I notice that there is also a 'programmers' network, and I don't even begin to know where that fits in. I, and I am assuming most people, will probably just post on Stack&nbsp;Overflow to be safe.  My question is, other than the short little description blurb of each one, is there a clear cut set of guidelines which what each network is intended for, what kinds of questions should go to each one, and is anything being done to encourage people to post in these newer, smaller (more specialized?) networks as opposed to just posting in big daddy Stack Overflow?  Now again, this is for computer science/programming/"why isn't this code doing what I want?" related questions, I am not saying that if I had a question about Linux or WordPress or something I would have the same confusion. What are suitable TV sizes and viewing distances for couch surfing on a 1080p LCD HDTV? Does the OP of a flagged post get comment notifications if the post is deleted by mods? I have noticed that when I leave comments on a question and someone votes it up, I do not get a notification. If the upvote count would at least be more than 5, I would expect to be notified since that leads to a badge. Kolmogorov-Smirnov two-sample $p$-values I am using the Kolmogorov&ndash;Smirnov two-sample test to compare distributions, and I noticed a $p$-value is frequently reported as the test statistic. How is this $p$-value determined? I know it's the probability of obtaining a result at least as large as the one obtained, but how is this $p$-value determined given this is a nonparametric test? That is, we can't assume Gaussian fluctuations in the distribution and compute the $p$-value using a $t$-test.  Thanks! Error in fontspec (my first question here) I'm using xelatex to compile this code:  \documentclass{book} \usepackage{fontspec}  \begin{document}  %This is a Greek text ``Ελλάδα'' text  \end{document}   and receive this error :  ("C:\Program Files\MiKTeX 2.9\tex\latex\fontspec\fontspec.cfg") ! Undefined control sequence. &lt;argument&gt; \LaTeX3 error:                             Erroneous variable \c__fontspec_shape_n_n_tl used! l.3806 \emfontdeclare{ \emshape, \eminnershape }   My aim is to make LaTeX compile greek letters properly in my pdf, but that's a different issue. I'm a little confused about the output I'm seeing in my routing table, particularly the 'metric' column:  $ route -n Kernel IP routing table Destination     Gateway         Genmask         Flags Metric Ref    Use Iface 0.0.0.0         192.168.0.1     0.0.0.0         UG    0      0        0 wlan0 172.16.35.0     0.0.0.0         255.255.255.0   U     0      0        0 vmnet1 192.168.0.0     0.0.0.0         255.255.255.0   U     9      0        0 wlan0 192.168.82.0    0.0.0.0         255.255.255.0   U     0      0        0 vmnet8   According to the man page, metric indicates the 'distance' to the target. I was a little confused about what exactly "target" was. I assumed it was my router (it goes to gateway 0.0.0.0, which then goes to my router at 192.168.0.1). Thus, I expected the metric to be a single hop to my router. However, it's 9! Why is this so number high? gnome-desktop-item-edit: command not found on Ubuntu 19.10 and later even with the 'gnome-panel' package installed What is a good book to learn number theory? What would be a good book to learn basic number theory? If possible a book which also has a collection of practice problems? Thanks. I am seeing quite a few conversions which have as source "accounts.google.com" (almost 40%).  AFAIK, in the new Universal Analytics as soon as a user has a Referrer set a new session is started. So if a user is getting on my page, and creates an account using social auth (e.g. Google accounts) when being redirected back, will this create a new session? I guess this would explain that there are many conversions coming from accounts.google.com - is it safe to enter accounts.google.com into the Referral Exclusion List? And more - what about Facebook logins, those would show up as facebook.com, but i probably don't want to exclude facebook.com as referrer?  Any ideas how to deal with UA referrers and social logins? How can I dynamically invoke a class method in PHP? The class method is not static. It appears that   call_user_func(...)   only works with static functions?  Thanks. Cannot create an array of LinkedLists in Java...? Mathematica envelope for the bottom of a plot, a generic function Same e-mail user, different address? I was wondering why using foo.bar@gmail.com works but not foo.bar@outlook.com.  In Gmail, foo.bar@gmail.com and foobar@gmail.com (and any combination of periods in the username) is equivalent.  Is this a hidden feature in Gmail? Which graphic file formats are supported by browsers? How to increase the signal power of a wi-fi card? I use an atheros card that requires ath9k driver. Are there any tools that can be used to increase the signal power of the wi-fi card? How to log commands within a "sudo su -"? If I:   [user@notebook ~] sudo echo 123456uu 123456uu [user@notebook ~]    Then I can see that in the logs:  [root@notebook /var/log] grep 123456uu * auth.log:Jan  9 17:01:51 notebook sudo: user : TTY=pts/3 ; PWD=/home/user ; USER=root ; COMMAND=/bin/echo 123456uu [root@notebook /var/log]    but if I:   [user@notebook ~] sudo su - [root@notebook ~] echo 1234567zz 1234567zz [root@notebook ~]    I cannot see it in the logs:   [root@notebook /var/log] grep 1234567zz * [root@notebook /var/log] echo $? 1 [root@notebook /var/log]    My question: How can I turn the logging on for the commands within the "sudo su -"?  OS is an Ubuntu 12.04 but the question is in general.   UPDATE#1:   [user@notebook ~] sudo su - [sudo] password for user:  [root@notebook ~] echo zizizi zizizi [root@notebook ~] cd /var/log [root@notebook /var/log] grep -iIR 'zizizi' * [root@notebook /var/log] grep 'COMMAND=/bin/su -' * auth.log:Jan 10 15:42:42 notebook sudo: user : TTY=pts/1 ; PWD=/home/user ; USER=root ; COMMAND=/bin/su - [root@notebook /var/log] crossfade between 2 videos using ffmpeg I've been trying to achieve a crossfade transition between 2 video clips using ffmpeg but have failed so far. I'm new to ffmpeg and am mostly relying on tweaking what I can find in the documentation and existing examples online. From what I read so far, using either the blend or overlay filter should help in achieving what I'm after but I can't figure out the command line details to get it to work.  The fade and concat filters are great for fade-out of video 1, fade-in to video 2 and concat the 2 into 1 clip type transitions but I'd appreciate help in getting a command to transition from video 1 to video 2 without any going to black in between. I couldn't find any examples for exactly this problem anywhere, maybe I'm looking for the wrong keywords...?  More speficially, my videos are mp4s (h264 video, no sound, in case that matters), each is 5 seconds long and I'm after a transition from approx. 4.5s of video 1 to 0.5s of video 2.  Similar to what this tutorial does using MLT and frames (see 2:25 for an example fade), though I'm looking for a way to do this just in ffmpeg without calling any other progs.   Any pointers or maybe a command line to get a fade like this would be much appreciated, thanks very much!