sed remove all lines starting with x or X, but the lines start with spaces I have to remove lines from a text starting with x or X, but the lines start with spaces. So far I have this: sed plik.txt -e &quot;/^[xX]/d&quot;  I have tried many combinations from other questions but nothing works. Here's the text:    Sed testing Testing             xTest test           test test test xxx XXX        X test test      End of text
sed : Ignore line starting whitespace for match I want to replace the default listening port of httpd to 9090. I can edit the line in httpd.conf file using below  sed -i "/^Listen/c\Listen 9090" /etc/httpd/conf/httpd.conf   But the line   Listen 80   may have white space before it.  How do I ignore this white space to match this line?
Can apostrophe 's' be used with 'etc.'? How to Setup GIMP 2.10 on Ubuntu 16.04 (Xenial Xerus) Use of inequality $1 - \cos (x) \leq x^2 /2$ In  answer the value of $1 - \cos(x)$ has to be evaluated in order to find its upper limit, if it exists.  In particular, $x = 2 \pi / n$. The answer is related to the length of a side of a regular $n$-gon inscribed into a unit-radius circumference; because the perimeter of the $n$-gon is always less than $2 \pi$, the single side must always be less than $2 \pi / n$.  The inequality  $$1 - \cos (x) \leq \displaystyle \frac{x^2}{2}$$ (1)  is used and the proof is completed with   $$2(1 - \cos(x)) \leq (2 \pi / n)^2$$  $$\sqrt{2(1 - \cos(x))} \leq 2 \pi / n$$  But it is well known that the cosine is a function $f(x) \in [-1;1]$, so $1 - \cos (x) \in [0,2]$. By using this information, we would obtain  $$1 - \cos (x) \leq 2$$ (2)  The proof would provide  $$2(1 - \cos(x)) \leq 4$$  $$\sqrt{2(1 - \cos(x))} \leq 2$$  which is a completely different result.   Why in that case it is preferable to use (1) instead of (2)? How to choose when it is convenient to use (1) and when to use (2) in a proof? Why am I getting black photos when I use the Manual feature on my DSLR? Triggered send status queued, need to get an alert Is there a way to conveniently define a C-like structure in Python? I'm tired of writing stuff like:  class MyStruct():     def __init__(self, field1, field2, field3):         self.field1 = field1         self.field2 = field2         self.field3 = field3 I get it after updating in Synaptic Manager  I recently did a clean install of Ubuntu 17.04 from 16.10.  error message:-  W: Download is performed unsandboxed as root as file '/var/cache/apt/archives/partial/samba-libs_2%3a4.5.8+dfsg-0ubuntu0.17.04.1_i386.deb' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) I need to show that for prime numbers of the form $p=4n+1$, $x=(2n)!$ solves the congruence $x^2 \equiv-1\pmod p$. I then need to show this implies p isn't a gaussian prime.   I have started to solve this using Wilson's theorem that a number $z$ is prime iff $(z-1)!\equiv-1\pmod z$. Therefore the endpoint of my proof should be that $(p-1)!\equiv-1\pmod p$.  As $p$ is of the form $p=4n+1$, I only need to prove that $4n!$ is congruent to $-1$ modulo $p$.   Here is my working so far: Starting with the congruence $x^2 \equiv -1\pmod p$:    $$\eqalign{x^2 = -1\pmod p&amp;\implies   x^2 + 1 = kp \implies (x-i)(x+i) = kp\cr &amp;\implies ((2n)!-i)((2n!)+i))=kp \implies 4n!- 1 =kp\cr}$$   This is where I start to run out of any ideas that seem to get me anywhere. Any tips would be greatly appreciated! How do I pass a function as a parameter to in elisp? I'm trying to pass one method to another in elisp, and then have that method execute it.  Here is an example:  (defun t1 ()   "t1")  (defun t2 ()   "t1")  (defun call-t (t)   ; how do I execute "t"?   (t))  ; How do I pass in method reference? (call-t 't1) I need assistance in integrating $ \frac{x \sin x}{1+(\cos x)^2}$ ArrayList object sorting confusion Event handler not working on dynamic content What is the "canary thread" and why is it starving? The following occasionally appears in /var/log/syslog:  rtkit-daemon[1145]: The canary thread is apparently starving. Taking action. rtkit-daemon[1145]: Demoting known real-time threads. rtkit-daemon[1145]: Successfully demoted thread 1431 of process 1368 (n/a). rtkit-daemon[1145]: Successfully demoted thread 1430 of process 1368 (n/a). rtkit-daemon[1145]: Successfully demoted thread 1368 of process 1368 (n/a). rtkit-daemon[1145]: Demoted 3 threads.   What's going on here? Why is my animation not keeping location and rotation correctly? I am currently 3d modeling a twisty puzzle and trying to animate it. I have the puzzle done but when I try to animate it, it randomly twists and turns the individual objects in different directions before converging back to their original form at the end of the animation.  The screencast of me attempting to animate this is here:   File at the end of the screencast:    This is the original file. Just delete the 2 keyframes that are there:    I did make this with a tutorial. It is by rcpongo and I have very slightly edited his design. All credit goes to him for my design. I updated to Ubuntu 20.04. When I use the default terminal, everything is fine. But if try to use terminator, I cannot use sudo. I get permission denied. Again, only when using terminator.  How can I sudo from the terminator? I really would like to continue to use a terminator.  Edit: I just also noted that it cannot find make either. I guess it's all messed up. I'll try to uninstall it and install again I guess. How do I calculate the probability density function for a joint beta + uniform distribution? The PDF of a Beta distribution is $$ f_X(x) = {{x^{a-1}(1-x)^{b-1}}\over {B(a,b)}}  $$ and CDF $$ F_X(x) =  I_x(a,b) $$ The PDF of a uniform distribution is $$ f_Y(y) =  {1 \over {b-a}} \space for \space  x \in [a,b] $$ and CDF $$ { x - a} \over {b - a} $$ I've know that if X and Y are two independent, continuous random variables, described by probability density functions above of $f_X(x)$ and $f_Y(x)$ then probability density function of $Z = XY$ is $$  f_Z(z) = \int_\infty^\infty f_X(x)f_Y({z\over x}){1\over abs(x)}dx  $$ but I'm struggling with the algebra to get  from this to the PDF and the CDF of the joint distribution. I'm using the uniform distribution between 0 and 1. n tasks assigned to n computers, what is the EX value of a computer getting 5 or more tasks? Apostrophes for possession: nouns My best friend of the moment - 'Essential Grammar in Use' for elementary students by Raymond Murphy - says that 'we normally use -'s for people.'     I stayed at my sister's house. (not the house of my sister).   Then, bellow in the same unit (64) says that 'we use of... for things, places, etc.'     Look at the roof of that building. (not that building's roof)   After that I thought:  Finally!!! I understand the rules for apostrophes!!!  But soon I lost all that naif excitement when I saw other written examples on the internet that were not following those 'rules'.     I've learnt that we can apply apostrophes to ...     one year's pay   and, finally, amazingly enough ... to , which means ANY kind of nouns (I deduce uncountable nouns are also part of the possibilities). This demolishes what is said in the grammar. So, it seems that eventually:     That building's roof -> is valid   So, now I need your help.    1) Can you tell me the rules concerning the apostrophe to show possession in respect to its usage with nouns? Can we really apply to all kind of nouns? e.g. teeth's, vehicle's, Paula's, forest's, manager's, Ireland's, etc     Scotland's worst drivers   Metadata improves information's accessibility       2) Is there a sense that justifies what is written in the grammar: 'we normally use -'s for people'? or it does not make sense at all? So, I was given the following problem as part of a homework assignment.     Suppose $f'(x) &gt; 0$ in $(a,b)$. Prove that $f$ is strictly increasing in $(a,b)$, and let $g$ be its inverse function. Prove that $g$ is differentiable, and that   $$g'(f(x)) = \frac{1}{f'(x)}$$   I have proven that $f$ is strictly increasing in $(a,b)$, and I could prove that $g'(f(x)) = 1/f'(x)$ if I could prove that $g$ is differentiable. The problem is that I am having trouble with a proof of that. Any advice?   Also, as a reference, this is exercise 5.2 from Baby Rudin. How to save an alias of an eval $(other_comand) command I've been using docker for a while and there's a command I write each time I boot up my docker:  eval $(docker-machine env)   I know eval shouldn't be used unless necessary, but it's mentioned by the following:  docker-machine env outputs environment variables like this:  docker-machine env export DOCKER_TLS_VERIFY="1" export DOCKER_HOST="tcp://&lt;some_ip&gt;:&lt;some_port&gt;" export DOCKER_CERT_PATH="/home/gableroux/.docker/machine/machines/default" export DOCKER_MACHINE_NAME="default" # Run this command to configure your shell:  # eval $(docker-machine env)   eval grabs these and load them in my current session.  Now what if I'd like to have an alias like this:  alias dockereval="eval $(docker-machine env)"   Syntax is good, but the problem is when a dotfile (let's say .zshrc as an example), well the content of the $() is evaluated when registering the alias when you source that file.  which dockereval   Results in  dockerenv: aliased to eval   I tried a few things like:  alias dockereval="docker-machine env | eval" alias dockereval="docker-machine env | /bin/bash" alias dockereval="eval `docker-machine env`"   but none did work. 2nd one is probably because it's running in a different session, 3rd does the same as $() I guess  Is there an other way to load these environment variables with an alias?