If they do I'd love to learn the names of them and what they do.
Linux determines the type of a file via a code in the file-header. It doesn't depend on file-extensions for to know which software is to use for opening the file.  That's what I remember from my education. Please correct me in case I'm wrong!  Working a bit with Ubuntu systems recently: I see a lot of files on the systems which have extensions like .sh, .txt, .o, .c  Now I'm wondering: Are these extensions are meant only for humans? So that one should get an idea what kind of file it is?  Or does they have some purpose for the operating-system too?
"Temporarily unreachable" when using fetch as Googlebot from Webmasters Tools The page I'm trying to fetch is public.  The server logs show no request.  Google reports that any page on my site is "Temporarily unreachable". It won't even fetch the verification file, a static HTML file that was successfully used to verify with the webmaster tool application itself.   My site is running on the .  What is causing this? I was reading a textbook. I found that it was mentioned the speed of sound increases with increase in temperature. But sound is a mechanical wave, and it travels faster when molecules are closer.   But an increase in temperature will draw molecules away from each other, and then accordingly the speed of sound should be slower. How is it possible that the speed of sound increases if temperature increases? What is the relation of speed of sound and temperature? I've read a new study which suggests that yawning may help you keep a cool head. Also, the findings might hold some hope for sufferers of insomnia, migraines, and even epilepsy.  Is there any conclusion about what the function of yawning is and why do we yawn? pyPdf for IndirectObject extraction Following this example, I can list all elements into a pdf file  import pyPdf pdf = pyPdf.PdfFileReader(open("pdffile.pdf")) list(pdf.pages) # Process all the objects. print pdf.resolvedObjects   now, I need to extract a non-standard object from the pdf file.   My object is the one named MYOBJECT and it is a string.  The piece printed by the python script that concernes me is:  {'/MYOBJECT': IndirectObject(584, 0)}   The pdf file is this:  558 0 obj &lt;&lt;/Contents 583 0 R/CropBox[0 0 595.22 842]/MediaBox[0 0 595.22 842]/Parent 29 0 R/Resources   &lt;&lt;/ColorSpace &lt;&lt;/CS0 563 0 R&gt;&gt;     /ExtGState &lt;&lt;/GS0 568 0 R&gt;&gt;     /Font&lt;&lt;/TT0 559 0 R/TT1 560 0 R/TT2 561 0 R/TT3 562 0 R&gt;&gt;     /ProcSet[/PDF/Text/ImageC]     /Properties&lt;&lt;/MC0&lt;&lt;/MYOBJECT 584 0 R&gt;&gt;/MC1&lt;&lt;/SubKey 582 0 R&gt;&gt; &gt;&gt;     /XObject&lt;&lt;/Im0 578 0 R&gt;&gt;&gt;&gt;   /Rotate 0/StructParents 0/Type/Page&gt;&gt; endobj ... ... ... 584 0 obj &lt;&lt;/Length 8&gt;&gt;stream  1_22_4_1     ---&gt;&gt;&gt;&gt;  this is the string I need to extract from the object  endstream endobj   How can I follow the 584 value in order to refer to my string (under pyPdf of course)?? semi filled circle How to set page geometry for a single page only? If $|\lbrace g \in G: \pi (g)=g^{-1} \rbrace|>\frac{3|G|}{4}$, then $G$ is an abelian group. Assume that $\pi$ is an automorphism of a finite group $G$. Let $S$ denote the set $\lbrace g \in G: \pi (g)=g^{-1} \rbrace$. Show that if $|S|&gt;\frac{3|G|}{4}$, then $G$ is an abelian group.    Anyone has any idea on how to solve this ? I have no idea how to start. How can I implement "cut outs" for lighting in OpenGL? Default constructor with empty brackets Windows Starter Edition, Home and Home Premium do not include gpedit, how do I install it? I want to make some changes to Windows that require using the Group Policy Editor (gpedit.msc).  Unfortunately the Group Policy Editor is not included with the Starter Edition, Home and Home Premium editions of Windows.  How can I install it? I want to create liveUSB on part of my flash stick. I made a partition with GParted and downloaded .iso file of Ubuntu 19 from the official website to mount with gnome-disk-utility.  I noticed that the iso file has "amd64" in the name. But I intend to use this USB not only on amd computers!  Is that important? Will the live USB work on PC with Intel/other processor? The website I'm working is allegedly going to have a massive hit rate soon after launch. The client is talking about the possibility  of around 2500 hits per second over a day or so.   Ignoring the fact that this hit rate is probably wild client optimism and apart from getting the largest servers possible, what is the best way that Drupal should be configured to support a large hit rate.  I've read Scaling the , ,  and many other pages, but what I'm looking for is real experience of doing this, what works, what doesn't, and what to expect. Let $p$ be an odd prime number. Prove that $$\left( \frac{1 \cdot 2}{p} \right) + \left( \frac{2 \cdot 3}{p} \right) + \left( \frac{3 \cdot 4}{p} \right) + \cdots + \left( \frac{(p-2)(p-1)}{p} \right) = -1$$ where $\left( \frac{a}{p}\right)$ is the Legendre symbol.  This seems to be a tricky one! I've tried using the property $\left( \frac{ab}{p} \right)=\left( \frac{a}{p}\right) \left( \frac{b}{p} \right)$ and prime factoring all the non-primes but to no avail. I had a quick thought of induction haha, but that was silly. I tried factoring the common Legendre symbols like $\left( \frac{3}{p}\right) \left[ \left( \frac{2}{p} \right) + \left( \frac{4}{p} \right) \right]$ but that didn't bring anything either. And I've been looking for pairwise cancellation with $1$ term leftover, but that does not seem to work.  Can you help? Recursively replace string in files I want to replace the backslash in the string page_path\example_filename.txt with a forward slash.  I also want to be able to run this on a large file system and have it recursively search all directories.  I found someone on the web who said to use grep, xargs, and sed but I wasn't able to get it to work. I've been trying different variations on delimiters and escape characters, but didn't get it.  Here is the command I was trying to run: grep -lr -e 'page_path\\' * | xargs sed -i 's/page_path\/page_path//g'  Thanks in advance. Given that $a,b,c$ are distinct positive real numbers, prove that $(a + b +c)\big( \frac1{a}+ \frac1{b} + \frac1{c}\big)&gt;9$   This is how I tried doing it:  Let $p= a + b + c,$ and $q=\frac1{a}+ \frac1{b} + \frac1{c}$.  Using AM>GM for $p, q$, I get:  $$\frac{p+q}{2} &gt; {(pq)}^{1/2}$$ $$\sqrt{(a + b +c)\bigg(\frac1{a}+ \frac1{b} + \frac1{c}\bigg)} &lt; \frac{\big(a+\frac1{a} + b+\frac1{b} + c+\frac1{c}\big)}2$$ And for any $x\in \mathbb{R}, \space \space x+\frac1{x}≥2.$ Thus,   $$(a + b +c)\bigg(\frac1{a}+ \frac1{b} + \frac1{c}\bigg)&lt;9, $$ which is the opposite of what had to be proven. What did I do wrong? How run a .jar file with a double-click? Difference between >> and >>> in verilog? What is the difference between &gt;&gt; and &gt;&gt;&gt; in verilog/system verilog? I know that == tests for only 1 and 0, while === tests for 1, 0, X, Z. So how is that similar to the shift operator? Get Edge / Vertex / Face from mouse position What has been proved about the big bang, and what has not? Ok so the universe is in constant expansion, that has been proven, right? And that means that it was smaller in the past.. But what's the smallest size we can be sure the universe has ever had?  I just want to know what's the oldest thing we are sure about. OEM license activation for Windows 10 Home VirtualBox guest, on Ubuntu host Context Three years ago my company got me a Lenovo T550 with Windows 10 Home installed on it (my understanding is that this is called &quot;OEM&quot;). I immediately erased everything to install Ubuntu on it. Unfortunately from now on I will need to use Windows 10 a few times a week for legacy reasons, but my main work is still on Ubuntu, so I am thinking of running Windows 10 within VirtualBox within Ubuntu. Lenovo recommendation Lenovo told me that my Windows Home license is somehow linked to my hardware (firmware?) and that Windows will automatically find this out. They pointed me to :  The installation of Microsoft Windows Server 2008,2008 R2 SP1, 2012, and 2012 R2 from Lenovo OEM media to such a virtual machine will fail until the virtual BIOS has been updated to include this information. setVMBIOS.exe performs this function for servers using Microsoft Hyper-V technology. Consult your hypervisor vendor for information on how to perform this function on other hypervisors. [...] The fix resolves this issue by adding Lenovo information to the virtual BIOS.  Note: That page does not mention Windows 10 Home, but I guess the same applies? VirtualBox How to apply Lenovo's recommendation to VirtualBox? (5.2.18) Right now I have out-of-the-box VirtualBox and the VM I created yesterday with standard settings does not activate:   Windows is not activated. Windows reported that no product key was found on your device. Error code: 0xC004F213